{"id":5163,"date":"2015-10-28T15:56:50","date_gmt":"2015-10-28T15:56:50","guid":{"rendered":"https:\/\/opentextbc.ca\/biology\/chapter\/24-4-hormonal-control-of-human-reproduction\/"},"modified":"2021-03-04T00:09:48","modified_gmt":"2021-03-04T00:09:48","slug":"24-4-hormonal-control-of-human-reproduction","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/biology\/chapter\/24-4-hormonal-control-of-human-reproduction\/","title":{"raw":"24.4.\u00a0Hormonal Control of Human Reproduction","rendered":"24.4.\u00a0Hormonal Control of Human Reproduction"},"content":{"raw":"<div class=\"titlepage\">\n<div class=\"abstract\">\n<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\nBy the end of this chapter, you will be able to:\n<div class=\"itemizedlist\">\n<ul class=\"itemizedlist\">\n \t<li class=\"listitem\">Describe the roles of male and female reproductive hormones<\/li>\n \t<li class=\"listitem\">Discuss the interplay of the ovarian and menstrual cycles<\/li>\n \t<li class=\"listitem\">Describe the process of menopause<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idm79404496\"> <\/span>The human male and female reproductive cycles are controlled by the interaction of hormones from the hypothalamus and anterior pituitary with hormones from reproductive tissues and organs. In both sexes, the hypothalamus monitors and causes the release of hormones from the pituitary gland. When the reproductive hormone is required, the hypothalamus sends a <strong>gonadotropin-releasing hormone (GnRH)<\/strong><a id=\"id857370\" class=\"indexterm\" href=\"\"><\/a> to the anterior pituitary. This causes the release of <span id=\"m44841-autoid-cnx2dbk-id1775068\"> <\/span><strong>follicle stimulating hormone (FSH)<\/strong><a id=\"id857385\" class=\"indexterm\" href=\"\"><\/a> and <span id=\"m44841-autoid-cnx2dbk-id1775072\"> <\/span><strong>luteinizing hormone (LH)<\/strong><a id=\"id857399\" class=\"indexterm\" href=\"\"><\/a> from the anterior pituitary into the blood. Note that the body must reach puberty in order for the adrenals to release the hormones that must be present for GnRH to be produced. Although FSH and LH are named after their functions in female reproduction, they are produced in both sexes and play important roles in controlling reproduction. Other hormones have specific functions in the male and female reproductive systems.\n<div class=\"section\" title=\"Male Hormones\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idp121831536\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Male Hormones<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idp77886272\"> <\/span>At the onset of puberty, the hypothalamus causes the release of FSH and LH into the male system for the first time. FSH enters the testes and stimulates the <span id=\"m44841-autoid-cnx2dbk-id1775096\"> <\/span><strong>Sertoli cells<\/strong> to begin facilitating spermatogenesis using negative feedback, as illustrated in\n\n<\/div>\n<a class=\"xref target-figure\" title=\"Figure\u00a043.14.\u00a0\" href=\"#attachment_1401\">Figure 24.14<\/a>. LH also enters the testes and stimulates the <span id=\"m44841-autoid-cnx2dbk-id1775106\"> <\/span><strong>interstitial cells of Leydig<\/strong> to make and release testosterone into the testes and the blood.\n\n<span id=\"m44841-fs-idm108547280\"> <\/span><span id=\"m44841-autoid-cnx2dbk-id1762952\"> <\/span><strong>Testosterone<\/strong><a id=\"id857477\" class=\"indexterm\" href=\"\"><\/a>, the hormone responsible for the secondary sexual characteristics that develop in the male during adolescence, stimulates spermatogenesis. These secondary sex characteristics include a deepening of the voice, the growth of facial, axillary, and pubic hair, and the beginnings of the sex drive.\n\n[caption id=\"attachment_1401\" align=\"aligncenter\" width=\"600\"]<a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_01.jpg\"><img class=\"wp-image-5159\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1.jpg\" alt=\"Figure_43_04_01\" width=\"600\" height=\"256\"><\/a> Figure 24.14.\u00a0 Hormones control sperm production in a negative feedback system.[\/caption]\n\n<div id=\"m44841-fig-ch43_04_01\" class=\"figure\" title=\"Figure\u00a043.14.\u00a0\">\n<div class=\"title\"><\/div>\n<span id=\"m44841-fs-idm49834240\"> <\/span>A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus and anterior pituitary to inhibit the release of GnRH, FSH, and LH. The Sertoli cells produce the hormone <span id=\"m44841-autoid-cnx2dbk-id1762997\"> <\/span><strong>inhibin<\/strong><a id=\"id857538\" class=\"indexterm\" href=\"\"><\/a>, which is released into the blood when the sperm count is too high. This inhibits the release of GnRH and FSH, which will cause spermatogenesis to slow down. If the sperm count reaches 20 million\/ml, the Sertoli cells cease the release of inhibin, and the sperm count increases.\n\n<\/div>\n<div class=\"section\" title=\"Female Hormones\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idm47116928\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Female Hormones<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idp93525568\"> <\/span>The control of reproduction in females is more complex. As with the male, the anterior pituitary hormones cause the release of the hormones FSH and LH. In addition, estrogens and progesterone are released from the developing follicles. <span id=\"m44841-autoid-cnx2dbk-id1796066\"> <\/span><strong>Estrogen<\/strong><a id=\"id857572\" class=\"indexterm\" href=\"\"><\/a> is the reproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption; it is also responsible for the secondary sexual characteristics of females. These include breast development, flaring of the hips, and a shorter period necessary for bone maturation. <span id=\"m44841-autoid-cnx2dbk-id1796072\"> <\/span><strong>Progesterone<\/strong><a id=\"id857589\" class=\"indexterm\" href=\"\"><\/a> assists in endometrial re-growth and inhibition of FSH and LH release.\n\n<span id=\"m44841-fs-idm47697408\"> <\/span>In females, FSH stimulates development of egg cells, called ova, which develop in structures called follicles. Follicle cells produce the hormone inhibin, which inhibits FSH production. LH also plays a role in the development of ova, induction of ovulation, and stimulation of estradiol and progesterone production by the ovaries. Estradiol and progesterone are steroid hormones that prepare the body for pregnancy. Estradiol produces secondary sex characteristics in females, while both estradiol and progesterone regulate the menstrual cycle.\n<div class=\"section\" title=\"The Ovarian Cycle and the Menstrual Cycle\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idp32933696\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">The Ovarian Cycle and the Menstrual Cycle<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idp35768912\"> <\/span><strong>The <span id=\"m44841-autoid-cnx2dbk-id1690759\"> <\/span>ovarian cycle<\/strong><a id=\"id857630\" class=\"indexterm\" href=\"\"><\/a> governs the preparation of endocrine tissues and release of eggs, while the <span id=\"m44841-autoid-cnx2dbk-id1690763\"> <\/span><strong>menstrual cycle<\/strong><a id=\"id857644\" class=\"indexterm\" href=\"\"><\/a> governs the preparation and maintenance of the uterine lining. These cycles occur concurrently and are coordinated over a 22\u201332 day cycle, with an average length of 28 days.\n\n<span id=\"m44841-fs-idp108162320\"> <\/span>The first half of the ovarian cycle is the follicular phase shown in <a class=\"xref target-figure\" title=\"Figure\u00a043.15.\u00a0\" href=\"#attachment_1402\">Figure 24.15<\/a>. Slowly rising levels of FSH and LH cause the growth of follicles on the surface of the ovary. This process prepares the egg for ovulation. As the follicles grow, they begin releasing estrogens and a low level of progesterone. Progesterone maintains the endometrium to help ensure pregnancy. The trip through the fallopian tube takes about seven days. At this stage of development, called the morula, there are 30-60 cells. If pregnancy implantation does not occur, the lining is sloughed off. After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase. The endometrium begins to regrow, replacing the blood vessels and glands that deteriorated during the end of the last cycle.\n<div id=\"m44841-fs-idp6751792\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fig-ch43_04_02\" class=\"figure\" title=\"Figure\u00a043.15.\u00a0\">\n<div class=\"body\">\n<div class=\"mediaobject\"><\/div>\n<div class=\"mediaobject\">\n\n[caption id=\"attachment_1402\" align=\"aligncenter\" width=\"600\"]<a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_02f.png\"><img class=\"wp-image-5160\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f.png\" alt=\"Figure_43_04_02f\" width=\"600\" height=\"609\"><\/a> Figure 24.15.\u00a0 The ovarian and menstrual cycles of female reproduction are regulated by hormones produced by the hypothalamus, pituitary, and ovaries.[\/caption]\n\n<\/div>\n<span id=\"m44841-fs-idm12233456\"> <\/span>Which of the following statements about hormone regulation of the female reproductive cycle is false?\n<div class=\"orderedlist\">\n<ol class=\"orderedlist\">\n \t<li class=\"listitem\">LH and FSH are produced in the pituitary, and estradiol and progesterone are produced in the ovaries.<\/li>\n \t<li class=\"listitem\">Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.<\/li>\n \t<li class=\"listitem\">Both progesterone and estradiol are produced by the follicles.<\/li>\n \t<li class=\"listitem\">Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idp22451904\"> <\/span>Just prior to the middle of the cycle (approximately day 14), the high level of estrogen causes FSH and especially LH to rise rapidly, then fall. The spike in LH causes <span id=\"m44841-autoid-cnx2dbk-id1760029\"> <\/span><strong>ovulation<\/strong>: the most mature follicle, like that shown in <a class=\"xref target-figure\" title=\"Figure\u00a043.16.\u00a0\" href=\"#attachment_1403\">Figure 24.16<\/a>, ruptures and releases its egg. The follicles that did not rupture degenerate and their eggs are lost. The level of estrogen decreases when the extra follicles degenerate.\n\n[caption id=\"attachment_1403\" align=\"aligncenter\" width=\"300\"]<a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_03.jpg\"><img class=\"wp-image-5161\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03.jpg\" alt=\"Figure_43_04_03\" width=\"300\" height=\"424\"><\/a> Figure 24.16.\u00a0 This mature egg follicle may rupture and release an egg. (credit: scale-bar data from Matt Russell)[\/caption]\n\n<span id=\"m44841-fs-idm95096192\"> <\/span>Following ovulation, the ovarian cycle enters its luteal phase, illustrated in <a class=\"xref target-figure\" title=\"Figure\u00a043.15.\u00a0\" href=\"#attachment_1402\">Figure 24.15<\/a> and the menstrual cycle enters its secretory phase, both of which run from about day 15 to 28. The luteal and secretory phases refer to changes in the ruptured follicle. The cells in the follicle undergo physical changes and produce a structure called a corpus luteum. The corpus luteum produces estrogen and progesterone. The progesterone facilitates the regrowth of the uterine lining and inhibits the release of further FSH and LH. The uterus is being prepared to accept a fertilized egg, should it occur during this cycle. The inhibition of FSH and LH prevents any further eggs and follicles from developing, while the progesterone is elevated. The level of estrogen produced by the corpus luteum increases to a steady level for the next few days.\n\n<span id=\"m44841-fs-idm149795664\"> <\/span>If no fertilized egg is implanted into the uterus, the corpus luteum degenerates and the levels of estrogen and progesterone decrease. The endometrium begins to degenerate as the progesterone levels drop, initiating the next menstrual cycle. The decrease in progesterone also allows the hypothalamus to send GnRH to the anterior pituitary, releasing FSH and LH and starting the cycles again. Figure 24.17 visually compares the ovarian and uterine cycles as well as the commensurate hormone levels.\n<div id=\"m44841-fs-idp24150368\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fig-ch43_04_04\" class=\"figure\" title=\"Figure\u00a043.17.\u00a0\">\n<div class=\"body\">\n<div class=\"mediaobject\"><\/div>\n<div class=\"mediaobject\">\n\n[caption id=\"attachment_1404\" align=\"aligncenter\" width=\"500\"]<a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_04.png\"><img class=\"wp-image-5162\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04.png\" alt=\"Figure_43_04_04\" width=\"500\" height=\"590\"><\/a> Figure 24.17.\u00a0 Rising and falling hormone levels result in progression of the ovarian and menstrual cycles. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)[\/caption]\n\n<\/div>\n<span id=\"m44841-fs-idp70242864\"> <\/span>Which of the following statements about the menstrual cycle is false?\n<div class=\"orderedlist\">\n<ol class=\"orderedlist\">\n \t<li class=\"listitem\">Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle.<\/li>\n \t<li class=\"listitem\">Menstruation occurs just after LH and FSH levels peak.<\/li>\n \t<li class=\"listitem\">Menstruation occurs after progesterone levels drop.<\/li>\n \t<li class=\"listitem\">Estrogen levels rise before ovulation, while progesterone levels rise after.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"section\" title=\"Menopause\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idm128602736\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Menopause<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<span id=\"m44841-fs-idp129033696\"> <\/span>As women approach their mid-40s to mid-50s, their ovaries begin to lose their sensitivity to FSH and LH. Menstrual periods become less frequent and finally cease; this is <span id=\"m44841-autoid-cnx2dbk-id1767630\"> <\/span><strong>menopause<\/strong><a id=\"id858012\" class=\"indexterm\" href=\"\"><\/a>. There are still eggs and potential follicles on the ovaries, but without the stimulation of FSH and LH, they will not produce a viable egg to be released. The outcome of this is the inability to have children.\n\n<span id=\"m44841-fs-idm107557984\"> <\/span>The side effects of menopause include hot flashes, heavy sweating (especially at night), headaches, some hair loss, muscle pain, vaginal dryness, insomnia, depression, weight gain, and mood swings. Estrogen is involved in calcium metabolism and, without it, blood levels of calcium decrease. To replenish the blood, calcium is lost from bone which may decrease the bone density and lead to osteoporosis. Supplementation of estrogen in the form of hormone replacement therapy (HRT) can prevent bone loss, but the therapy can have negative side effects. While HRT is thought to give some protection from colon cancer, osteoporosis, heart disease, macular degeneration, and possibly depression, its negative side effects include increased risk of: stroke or heart attack, blood clots, breast cancer, ovarian cancer, endometrial cancer, gall bladder disease, and possibly dementia.\n<div id=\"m44841-fs-idm28103312\" class=\"note career\">\n<div class=\"title\">\n<div class=\"body\">\n<h2 class=\"title\">Reproductive Endocrinologist<\/h2>\nA reproductive endocrinologist is a physician who treats a variety of hormonal disorders related to reproduction and infertility in both men and women. The disorders include menstrual problems, infertility, pregnancy loss, sexual dysfunction, and menopause. Doctors may use fertility drugs, surgery, or assisted reproductive techniques (ART) in their therapy. ART involves the use of procedures to manipulate the egg or sperm to facilitate reproduction, such as <span class=\"emphasis\"><em>in vitro<\/em><\/span> fertilization.\n\n<span id=\"m44841-fs-idm74481808\"> <\/span>Reproductive endocrinologists undergo extensive medical training, first in a four-year residency in obstetrics and gynecology, then in a three-year fellowship in reproductive endocrinology. To be board certified in this area, the physician must pass written and oral exams in both areas.\n\n<\/div>\n<\/div>\n<h2>Summary<\/h2>\n<p style=\"text-align: left;\">The male and female reproductive cycles are controlled by hormones released from the hypothalamus and anterior pituitary as well as hormones from reproductive tissues and organs. The hypothalamus monitors the need for the FSH and LH hormones made and released from the anterior pituitary. FSH and LH affect reproductive structures to cause the formation of sperm and the preparation of eggs for release and possible fertilization. In the male, FSH and LH stimulate Sertoli cells and interstitial cells of Leydig in the testes to facilitate sperm production. The Leydig cells produce testosterone, which also is responsible for the secondary sexual characteristics of males. In females, FSH and LH cause estrogen and progesterone to be produced. They regulate the female reproductive system which is divided into the ovarian cycle and the menstrual cycle. Menopause occurs when the ovaries lose their sensitivity to FSH and LH and the female reproductive cycles slow to a stop.<\/p>\n\n<div class=\"textbox exercises\">\n<h3>Exercises<\/h3>\n<ol>\n \t<li>Which of the following statements about hormone regulation of the female reproductive cycle is false?\n<ol>\n \t<li>LH and FSH are produced in the pituitary, and estradiol and progesterone are produced in the ovaries.<\/li>\n \t<li>Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.<\/li>\n \t<li>Both progesterone and estradiol are produced by the follicles.<\/li>\n \t<li>Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol.<\/li>\n<\/ol>\n<\/li>\n \t<li>Which of the following statements about the menstrual cycle is false?\n<ol>\n \t<li>Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle.<\/li>\n \t<li>Menstruation occurs just after LH and FSH levels peak.<\/li>\n \t<li>Menstruation occurs after progesterone levels drop.<\/li>\n \t<li>Estrogen levels rise before ovulation, while progesterone levels rise after.<\/li>\n<\/ol>\n<\/li>\n \t<li><span id=\"m44841-fs-idp98847168\"><span id=\"m44841-fs-idm63973888\">Which hormone causes Leydig cells to make testosterone?<\/span><\/span>\n<ol>\n \t<li>FSH<\/li>\n \t<li>LH<\/li>\n \t<li>inhibin<\/li>\n \t<li>estrogen<\/li>\n<\/ol>\n<\/li>\n \t<li>Which hormone causes FSH and LH to be released?\n<ol>\n \t<li>testosterone<\/li>\n \t<li>estrogen<\/li>\n \t<li>GnRH<\/li>\n \t<li>progesterone<\/li>\n<\/ol>\n<\/li>\n \t<li>Which hormone signals ovulation?\n<ol>\n \t<li>FSH<\/li>\n \t<li>LH<\/li>\n \t<li>inhibin<\/li>\n \t<li>estrogen<\/li>\n<\/ol>\n<\/li>\n \t<li><span id=\"m44841-fs-idm134911664\">Which hormone causes the re-growth of the endometrial lining of the uterus?<\/span>\n<ol>\n \t<li>testosterone<\/li>\n \t<li>estrogen<\/li>\n \t<li>GnRH<\/li>\n \t<li>progesterone<\/li>\n<\/ol>\n<\/li>\n \t<li><span id=\"m44841-fs-idp67055712\"> <\/span>If male reproductive pathways are not cyclical, how are they controlled?<\/li>\n \t<li>Describe the events in the ovarian cycle leading up to ovulation.<\/li>\n<\/ol>\n<strong>Answers<\/strong>\n<ol>\n \t<li>C<\/li>\n \t<li>B<\/li>\n \t<li>A<\/li>\n \t<li>C<\/li>\n \t<li>B<\/li>\n \t<li>D<\/li>\n \t<li>Negative feedback in the male system is supplied through two hormones: inhibin and testosterone. Inhibin is produced by Sertoli cells when the sperm count exceeds set limits. The hormone inhibits GnRH and FSH, decreasing the activity of the Sertoli cells. Increased levels of testosterone affect the release of both GnRH and LH, decreasing the activity of the Leydig cells, resulting in decreased testosterone and sperm production.<\/li>\n \t<li>Low levels of progesterone allow the hypothalamus to send GnRH to the anterior pituitary and cause the release of FSH and LH. FSH stimulates follicles on the ovary to grow and prepare the eggs for ovulation. As the follicles increase in size, they begin to release estrogen and a low level of progesterone into the blood. The level of estrogen rises to a peak, causing a spike in the concentration of LH. This causes the most mature follicle to rupture and ovulation occurs.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"m44841-fs-idm55845888\" class=\"exercise\">\n<div id=\"m44841-fs-idm171491232\" class=\"exercise\">\n<div id=\"m44841-fs-idm71478992\" class=\"exercise\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm36439968\" class=\"solution labeled\">\n<div class=\"body\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm112725344\" class=\"exercise\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm12075648\" class=\"solution labeled\">\n<div class=\"body\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"bcc-box bcc-success\">\n<h3>Glossary<\/h3>\n<strong>estrogen<\/strong>\nreproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption\n\n<strong>follicle stimulating hormone (FSH)<\/strong>\nreproductive hormone that causes sperm production in men and follicle development in women\n\n<strong>gonadotropin-releasing hormone (GnRH)<\/strong>\nhormone from the hypothalamus that causes the release of FSH and LH from the anterior pituitary\n\n<strong>inhibin<\/strong>\nhormone made by Sertoli cells; provides negative feedback to hypothalamus in control of FSH and GnRH release\n\n<strong>interstitial<\/strong>\ncell of Leydigcell in seminiferous tubules that makes testosterone\n\n<strong>luteinizing hormone (LH)<\/strong>\nreproductive hormone in both men and women, causes testosterone production in men and ovulation and lactation in women\n\n<strong>menopause<\/strong>\nloss of reproductive capacity in women due to decreased sensitivity of the ovaries to FSH and LH\n\n<strong>menstrual cycle<\/strong>\ncycle of the degradation and re-growth of the endometrium\n\n<strong>ovarian cycle<\/strong>\ncycle of preparation of egg for ovulation and the conversion of the follicle to the corpus luteum\n\n<strong>ovulation<\/strong>\nrelease of the egg by the most mature follicle\n\n<strong>progesterone<\/strong>\nreproductive hormone in women; assists in endometrial re-growth and inhibition of FSH and LH release\n\n<strong>Sertoli cell<\/strong>\ncell in seminiferous tubules that assists developing sperm and makes inhibin\n\n<strong>testosterone<\/strong>\nreproductive hormone in men that assists in sperm production and promoting secondary sexual characteristics\n\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>","rendered":"<div class=\"titlepage\">\n<div class=\"abstract\">\n<div class=\"bcc-box bcc-highlight\">\n<h3>Learning Objectives<\/h3>\n<p>By the end of this chapter, you will be able to:<\/p>\n<div class=\"itemizedlist\">\n<ul class=\"itemizedlist\">\n<li class=\"listitem\">Describe the roles of male and female reproductive hormones<\/li>\n<li class=\"listitem\">Discuss the interplay of the ovarian and menstrual cycles<\/li>\n<li class=\"listitem\">Describe the process of menopause<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idm79404496\"> <\/span>The human male and female reproductive cycles are controlled by the interaction of hormones from the hypothalamus and anterior pituitary with hormones from reproductive tissues and organs. In both sexes, the hypothalamus monitors and causes the release of hormones from the pituitary gland. When the reproductive hormone is required, the hypothalamus sends a <strong>gonadotropin-releasing hormone (GnRH)<\/strong><a id=\"id857370\" class=\"indexterm\" href=\"\"><\/a> to the anterior pituitary. This causes the release of <span id=\"m44841-autoid-cnx2dbk-id1775068\"> <\/span><strong>follicle stimulating hormone (FSH)<\/strong><a id=\"id857385\" class=\"indexterm\" href=\"\"><\/a> and <span id=\"m44841-autoid-cnx2dbk-id1775072\"> <\/span><strong>luteinizing hormone (LH)<\/strong><a id=\"id857399\" class=\"indexterm\" href=\"\"><\/a> from the anterior pituitary into the blood. Note that the body must reach puberty in order for the adrenals to release the hormones that must be present for GnRH to be produced. Although FSH and LH are named after their functions in female reproduction, they are produced in both sexes and play important roles in controlling reproduction. Other hormones have specific functions in the male and female reproductive systems.<\/p>\n<div class=\"section\" title=\"Male Hormones\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idp121831536\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Male Hormones<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idp77886272\"> <\/span>At the onset of puberty, the hypothalamus causes the release of FSH and LH into the male system for the first time. FSH enters the testes and stimulates the <span id=\"m44841-autoid-cnx2dbk-id1775096\"> <\/span><strong>Sertoli cells<\/strong> to begin facilitating spermatogenesis using negative feedback, as illustrated in<\/p>\n<\/div>\n<p><a class=\"xref target-figure\" title=\"Figure\u00a043.14.\u00a0\" href=\"#attachment_1401\">Figure 24.14<\/a>. LH also enters the testes and stimulates the <span id=\"m44841-autoid-cnx2dbk-id1775106\"> <\/span><strong>interstitial cells of Leydig<\/strong> to make and release testosterone into the testes and the blood.<\/p>\n<p><span id=\"m44841-fs-idm108547280\"> <\/span><span id=\"m44841-autoid-cnx2dbk-id1762952\"> <\/span><strong>Testosterone<\/strong><a id=\"id857477\" class=\"indexterm\" href=\"\"><\/a>, the hormone responsible for the secondary sexual characteristics that develop in the male during adolescence, stimulates spermatogenesis. These secondary sex characteristics include a deepening of the voice, the growth of facial, axillary, and pubic hair, and the beginnings of the sex drive.<\/p>\n<figure id=\"attachment_1401\" aria-describedby=\"caption-attachment-1401\" style=\"width: 600px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_01.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5159\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1.jpg\" alt=\"Figure_43_04_01\" width=\"600\" height=\"256\" srcset=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1.jpg 1024w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1-300x128.jpg 300w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1-768x327.jpg 768w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1-65x28.jpg 65w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1-225x96.jpg 225w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/10\/Figure_43_04_01-1024x436-1-350x149.jpg 350w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-1401\" class=\"wp-caption-text\">Figure 24.14.\u00a0 Hormones control sperm production in a negative feedback system.<\/figcaption><\/figure>\n<div id=\"m44841-fig-ch43_04_01\" class=\"figure\" title=\"Figure\u00a043.14.\u00a0\">\n<div class=\"title\"><\/div>\n<p><span id=\"m44841-fs-idm49834240\"> <\/span>A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus and anterior pituitary to inhibit the release of GnRH, FSH, and LH. The Sertoli cells produce the hormone <span id=\"m44841-autoid-cnx2dbk-id1762997\"> <\/span><strong>inhibin<\/strong><a id=\"id857538\" class=\"indexterm\" href=\"\"><\/a>, which is released into the blood when the sperm count is too high. This inhibits the release of GnRH and FSH, which will cause spermatogenesis to slow down. If the sperm count reaches 20 million\/ml, the Sertoli cells cease the release of inhibin, and the sperm count increases.<\/p>\n<\/div>\n<div class=\"section\" title=\"Female Hormones\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idm47116928\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Female Hormones<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idp93525568\"> <\/span>The control of reproduction in females is more complex. As with the male, the anterior pituitary hormones cause the release of the hormones FSH and LH. In addition, estrogens and progesterone are released from the developing follicles. <span id=\"m44841-autoid-cnx2dbk-id1796066\"> <\/span><strong>Estrogen<\/strong><a id=\"id857572\" class=\"indexterm\" href=\"\"><\/a> is the reproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption; it is also responsible for the secondary sexual characteristics of females. These include breast development, flaring of the hips, and a shorter period necessary for bone maturation. <span id=\"m44841-autoid-cnx2dbk-id1796072\"> <\/span><strong>Progesterone<\/strong><a id=\"id857589\" class=\"indexterm\" href=\"\"><\/a> assists in endometrial re-growth and inhibition of FSH and LH release.<\/p>\n<p><span id=\"m44841-fs-idm47697408\"> <\/span>In females, FSH stimulates development of egg cells, called ova, which develop in structures called follicles. Follicle cells produce the hormone inhibin, which inhibits FSH production. LH also plays a role in the development of ova, induction of ovulation, and stimulation of estradiol and progesterone production by the ovaries. Estradiol and progesterone are steroid hormones that prepare the body for pregnancy. Estradiol produces secondary sex characteristics in females, while both estradiol and progesterone regulate the menstrual cycle.<\/p>\n<div class=\"section\" title=\"The Ovarian Cycle and the Menstrual Cycle\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idp32933696\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">The Ovarian Cycle and the Menstrual Cycle<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idp35768912\"> <\/span><strong>The <span id=\"m44841-autoid-cnx2dbk-id1690759\"> <\/span>ovarian cycle<\/strong><a id=\"id857630\" class=\"indexterm\" href=\"\"><\/a> governs the preparation of endocrine tissues and release of eggs, while the <span id=\"m44841-autoid-cnx2dbk-id1690763\"> <\/span><strong>menstrual cycle<\/strong><a id=\"id857644\" class=\"indexterm\" href=\"\"><\/a> governs the preparation and maintenance of the uterine lining. These cycles occur concurrently and are coordinated over a 22\u201332 day cycle, with an average length of 28 days.<\/p>\n<p><span id=\"m44841-fs-idp108162320\"> <\/span>The first half of the ovarian cycle is the follicular phase shown in <a class=\"xref target-figure\" title=\"Figure\u00a043.15.\u00a0\" href=\"#attachment_1402\">Figure 24.15<\/a>. Slowly rising levels of FSH and LH cause the growth of follicles on the surface of the ovary. This process prepares the egg for ovulation. As the follicles grow, they begin releasing estrogens and a low level of progesterone. Progesterone maintains the endometrium to help ensure pregnancy. The trip through the fallopian tube takes about seven days. At this stage of development, called the morula, there are 30-60 cells. If pregnancy implantation does not occur, the lining is sloughed off. After about five days, estrogen levels rise and the menstrual cycle enters the proliferative phase. The endometrium begins to regrow, replacing the blood vessels and glands that deteriorated during the end of the last cycle.<\/p>\n<div id=\"m44841-fs-idp6751792\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fig-ch43_04_02\" class=\"figure\" title=\"Figure\u00a043.15.\u00a0\">\n<div class=\"body\">\n<div class=\"mediaobject\"><\/div>\n<div class=\"mediaobject\">\n<figure id=\"attachment_1402\" aria-describedby=\"caption-attachment-1402\" style=\"width: 600px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_02f.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5160\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f.png\" alt=\"Figure_43_04_02f\" width=\"600\" height=\"609\" srcset=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f.png 950w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f-296x300.png 296w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f-768x779.png 768w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f-65x66.png 65w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f-225x228.png 225w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_02f-350x355.png 350w\" sizes=\"auto, (max-width: 600px) 100vw, 600px\" \/><\/a><figcaption id=\"caption-attachment-1402\" class=\"wp-caption-text\">Figure 24.15.\u00a0 The ovarian and menstrual cycles of female reproduction are regulated by hormones produced by the hypothalamus, pituitary, and ovaries.<\/figcaption><\/figure>\n<\/div>\n<p><span id=\"m44841-fs-idm12233456\"> <\/span>Which of the following statements about hormone regulation of the female reproductive cycle is false?<\/p>\n<div class=\"orderedlist\">\n<ol class=\"orderedlist\">\n<li class=\"listitem\">LH and FSH are produced in the pituitary, and estradiol and progesterone are produced in the ovaries.<\/li>\n<li class=\"listitem\">Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.<\/li>\n<li class=\"listitem\">Both progesterone and estradiol are produced by the follicles.<\/li>\n<li class=\"listitem\">Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idp22451904\"> <\/span>Just prior to the middle of the cycle (approximately day 14), the high level of estrogen causes FSH and especially LH to rise rapidly, then fall. The spike in LH causes <span id=\"m44841-autoid-cnx2dbk-id1760029\"> <\/span><strong>ovulation<\/strong>: the most mature follicle, like that shown in <a class=\"xref target-figure\" title=\"Figure\u00a043.16.\u00a0\" href=\"#attachment_1403\">Figure 24.16<\/a>, ruptures and releases its egg. The follicles that did not rupture degenerate and their eggs are lost. The level of estrogen decreases when the extra follicles degenerate.<\/p>\n<figure id=\"attachment_1403\" aria-describedby=\"caption-attachment-1403\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_03.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5161\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03.jpg\" alt=\"Figure_43_04_03\" width=\"300\" height=\"424\" srcset=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03.jpg 544w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03-212x300.jpg 212w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03-65x92.jpg 65w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03-225x318.jpg 225w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_03-350x495.jpg 350w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-1403\" class=\"wp-caption-text\">Figure 24.16.\u00a0 This mature egg follicle may rupture and release an egg. (credit: scale-bar data from Matt Russell)<\/figcaption><\/figure>\n<p><span id=\"m44841-fs-idm95096192\"> <\/span>Following ovulation, the ovarian cycle enters its luteal phase, illustrated in <a class=\"xref target-figure\" title=\"Figure\u00a043.15.\u00a0\" href=\"#attachment_1402\">Figure 24.15<\/a> and the menstrual cycle enters its secretory phase, both of which run from about day 15 to 28. The luteal and secretory phases refer to changes in the ruptured follicle. The cells in the follicle undergo physical changes and produce a structure called a corpus luteum. The corpus luteum produces estrogen and progesterone. The progesterone facilitates the regrowth of the uterine lining and inhibits the release of further FSH and LH. The uterus is being prepared to accept a fertilized egg, should it occur during this cycle. The inhibition of FSH and LH prevents any further eggs and follicles from developing, while the progesterone is elevated. The level of estrogen produced by the corpus luteum increases to a steady level for the next few days.<\/p>\n<p><span id=\"m44841-fs-idm149795664\"> <\/span>If no fertilized egg is implanted into the uterus, the corpus luteum degenerates and the levels of estrogen and progesterone decrease. The endometrium begins to degenerate as the progesterone levels drop, initiating the next menstrual cycle. The decrease in progesterone also allows the hypothalamus to send GnRH to the anterior pituitary, releasing FSH and LH and starting the cycles again. Figure 24.17 visually compares the ovarian and uterine cycles as well as the commensurate hormone levels.<\/p>\n<div id=\"m44841-fs-idp24150368\" class=\"note art-connection\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fig-ch43_04_04\" class=\"figure\" title=\"Figure\u00a043.17.\u00a0\">\n<div class=\"body\">\n<div class=\"mediaobject\"><\/div>\n<div class=\"mediaobject\">\n<figure id=\"attachment_1404\" aria-describedby=\"caption-attachment-1404\" style=\"width: 500px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2015\/03\/Figure_43_04_04.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5162\" src=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04.png\" alt=\"Figure_43_04_04\" width=\"500\" height=\"590\" srcset=\"https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04.png 725w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04-254x300.png 254w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04-65x77.png 65w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04-225x265.png 225w, https:\/\/opentextbc.ca\/biology\/wp-content\/uploads\/sites\/96\/2021\/03\/Figure_43_04_04-350x413.png 350w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/a><figcaption id=\"caption-attachment-1404\" class=\"wp-caption-text\">Figure 24.17.\u00a0 Rising and falling hormone levels result in progression of the ovarian and menstrual cycles. (credit: modification of work by Mikael H\u00e4ggstr\u00f6m)<\/figcaption><\/figure>\n<\/div>\n<p><span id=\"m44841-fs-idp70242864\"> <\/span>Which of the following statements about the menstrual cycle is false?<\/p>\n<div class=\"orderedlist\">\n<ol class=\"orderedlist\">\n<li class=\"listitem\">Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle.<\/li>\n<li class=\"listitem\">Menstruation occurs just after LH and FSH levels peak.<\/li>\n<li class=\"listitem\">Menstruation occurs after progesterone levels drop.<\/li>\n<li class=\"listitem\">Estrogen levels rise before ovulation, while progesterone levels rise after.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"section\" title=\"Menopause\">\n<div class=\"titlepage\">\n<div>\n<div>\n<h2 id=\"m44841-fs-idm128602736\"><span class=\"cnx-gentext-section cnx-gentext-autogenerated\"><span class=\"cnx-gentext-section cnx-gentext-t\">Menopause<\/span><\/span><\/h2>\n<\/div>\n<\/div>\n<\/div>\n<p><span id=\"m44841-fs-idp129033696\"> <\/span>As women approach their mid-40s to mid-50s, their ovaries begin to lose their sensitivity to FSH and LH. Menstrual periods become less frequent and finally cease; this is <span id=\"m44841-autoid-cnx2dbk-id1767630\"> <\/span><strong>menopause<\/strong><a id=\"id858012\" class=\"indexterm\" href=\"\"><\/a>. There are still eggs and potential follicles on the ovaries, but without the stimulation of FSH and LH, they will not produce a viable egg to be released. The outcome of this is the inability to have children.<\/p>\n<p><span id=\"m44841-fs-idm107557984\"> <\/span>The side effects of menopause include hot flashes, heavy sweating (especially at night), headaches, some hair loss, muscle pain, vaginal dryness, insomnia, depression, weight gain, and mood swings. Estrogen is involved in calcium metabolism and, without it, blood levels of calcium decrease. To replenish the blood, calcium is lost from bone which may decrease the bone density and lead to osteoporosis. Supplementation of estrogen in the form of hormone replacement therapy (HRT) can prevent bone loss, but the therapy can have negative side effects. While HRT is thought to give some protection from colon cancer, osteoporosis, heart disease, macular degeneration, and possibly depression, its negative side effects include increased risk of: stroke or heart attack, blood clots, breast cancer, ovarian cancer, endometrial cancer, gall bladder disease, and possibly dementia.<\/p>\n<div id=\"m44841-fs-idm28103312\" class=\"note career\">\n<div class=\"title\">\n<div class=\"body\">\n<h2 class=\"title\">Reproductive Endocrinologist<\/h2>\n<p>A reproductive endocrinologist is a physician who treats a variety of hormonal disorders related to reproduction and infertility in both men and women. The disorders include menstrual problems, infertility, pregnancy loss, sexual dysfunction, and menopause. Doctors may use fertility drugs, surgery, or assisted reproductive techniques (ART) in their therapy. ART involves the use of procedures to manipulate the egg or sperm to facilitate reproduction, such as <span class=\"emphasis\"><em>in vitro<\/em><\/span> fertilization.<\/p>\n<p><span id=\"m44841-fs-idm74481808\"> <\/span>Reproductive endocrinologists undergo extensive medical training, first in a four-year residency in obstetrics and gynecology, then in a three-year fellowship in reproductive endocrinology. To be board certified in this area, the physician must pass written and oral exams in both areas.<\/p>\n<\/div>\n<\/div>\n<h2>Summary<\/h2>\n<p style=\"text-align: left;\">The male and female reproductive cycles are controlled by hormones released from the hypothalamus and anterior pituitary as well as hormones from reproductive tissues and organs. The hypothalamus monitors the need for the FSH and LH hormones made and released from the anterior pituitary. FSH and LH affect reproductive structures to cause the formation of sperm and the preparation of eggs for release and possible fertilization. In the male, FSH and LH stimulate Sertoli cells and interstitial cells of Leydig in the testes to facilitate sperm production. The Leydig cells produce testosterone, which also is responsible for the secondary sexual characteristics of males. In females, FSH and LH cause estrogen and progesterone to be produced. They regulate the female reproductive system which is divided into the ovarian cycle and the menstrual cycle. Menopause occurs when the ovaries lose their sensitivity to FSH and LH and the female reproductive cycles slow to a stop.<\/p>\n<div class=\"textbox exercises\">\n<h3>Exercises<\/h3>\n<ol>\n<li>Which of the following statements about hormone regulation of the female reproductive cycle is false?\n<ol>\n<li>LH and FSH are produced in the pituitary, and estradiol and progesterone are produced in the ovaries.<\/li>\n<li>Estradiol and progesterone secreted from the corpus luteum cause the endometrium to thicken.<\/li>\n<li>Both progesterone and estradiol are produced by the follicles.<\/li>\n<li>Secretion of GnRH by the hypothalamus is inhibited by low levels of estradiol but stimulated by high levels of estradiol.<\/li>\n<\/ol>\n<\/li>\n<li>Which of the following statements about the menstrual cycle is false?\n<ol>\n<li>Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle.<\/li>\n<li>Menstruation occurs just after LH and FSH levels peak.<\/li>\n<li>Menstruation occurs after progesterone levels drop.<\/li>\n<li>Estrogen levels rise before ovulation, while progesterone levels rise after.<\/li>\n<\/ol>\n<\/li>\n<li><span id=\"m44841-fs-idp98847168\"><span id=\"m44841-fs-idm63973888\">Which hormone causes Leydig cells to make testosterone?<\/span><\/span>\n<ol>\n<li>FSH<\/li>\n<li>LH<\/li>\n<li>inhibin<\/li>\n<li>estrogen<\/li>\n<\/ol>\n<\/li>\n<li>Which hormone causes FSH and LH to be released?\n<ol>\n<li>testosterone<\/li>\n<li>estrogen<\/li>\n<li>GnRH<\/li>\n<li>progesterone<\/li>\n<\/ol>\n<\/li>\n<li>Which hormone signals ovulation?\n<ol>\n<li>FSH<\/li>\n<li>LH<\/li>\n<li>inhibin<\/li>\n<li>estrogen<\/li>\n<\/ol>\n<\/li>\n<li><span id=\"m44841-fs-idm134911664\">Which hormone causes the re-growth of the endometrial lining of the uterus?<\/span>\n<ol>\n<li>testosterone<\/li>\n<li>estrogen<\/li>\n<li>GnRH<\/li>\n<li>progesterone<\/li>\n<\/ol>\n<\/li>\n<li><span id=\"m44841-fs-idp67055712\"> <\/span>If male reproductive pathways are not cyclical, how are they controlled?<\/li>\n<li>Describe the events in the ovarian cycle leading up to ovulation.<\/li>\n<\/ol>\n<p><strong>Answers<\/strong><\/p>\n<ol>\n<li>C<\/li>\n<li>B<\/li>\n<li>A<\/li>\n<li>C<\/li>\n<li>B<\/li>\n<li>D<\/li>\n<li>Negative feedback in the male system is supplied through two hormones: inhibin and testosterone. Inhibin is produced by Sertoli cells when the sperm count exceeds set limits. The hormone inhibits GnRH and FSH, decreasing the activity of the Sertoli cells. Increased levels of testosterone affect the release of both GnRH and LH, decreasing the activity of the Leydig cells, resulting in decreased testosterone and sperm production.<\/li>\n<li>Low levels of progesterone allow the hypothalamus to send GnRH to the anterior pituitary and cause the release of FSH and LH. FSH stimulates follicles on the ovary to grow and prepare the eggs for ovulation. As the follicles increase in size, they begin to release estrogen and a low level of progesterone into the blood. The level of estrogen rises to a peak, causing a spike in the concentration of LH. This causes the most mature follicle to rupture and ovulation occurs.<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"m44841-fs-idm55845888\" class=\"exercise\">\n<div id=\"m44841-fs-idm171491232\" class=\"exercise\">\n<div id=\"m44841-fs-idm71478992\" class=\"exercise\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm36439968\" class=\"solution labeled\">\n<div class=\"body\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm112725344\" class=\"exercise\">\n<div class=\"title\">\n<div class=\"body\">\n<div id=\"m44841-fs-idm12075648\" class=\"solution labeled\">\n<div class=\"body\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"bcc-box bcc-success\">\n<h3>Glossary<\/h3>\n<p><strong>estrogen<\/strong><br \/>\nreproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption<\/p>\n<p><strong>follicle stimulating hormone (FSH)<\/strong><br \/>\nreproductive hormone that causes sperm production in men and follicle development in women<\/p>\n<p><strong>gonadotropin-releasing hormone (GnRH)<\/strong><br \/>\nhormone from the hypothalamus that causes the release of FSH and LH from the anterior pituitary<\/p>\n<p><strong>inhibin<\/strong><br \/>\nhormone made by Sertoli cells; provides negative feedback to hypothalamus in control of FSH and GnRH release<\/p>\n<p><strong>interstitial<\/strong><br \/>\ncell of Leydigcell in seminiferous tubules that makes testosterone<\/p>\n<p><strong>luteinizing hormone (LH)<\/strong><br \/>\nreproductive hormone in both men and women, causes testosterone production in men and ovulation and lactation in women<\/p>\n<p><strong>menopause<\/strong><br \/>\nloss of reproductive capacity in women due to decreased sensitivity of the ovaries to FSH and LH<\/p>\n<p><strong>menstrual cycle<\/strong><br \/>\ncycle of the degradation and re-growth of the endometrium<\/p>\n<p><strong>ovarian cycle<\/strong><br \/>\ncycle of preparation of egg for ovulation and the conversion of the follicle to the corpus luteum<\/p>\n<p><strong>ovulation<\/strong><br \/>\nrelease of the egg by the most mature follicle<\/p>\n<p><strong>progesterone<\/strong><br \/>\nreproductive hormone in women; assists in endometrial re-growth and inhibition of FSH and LH release<\/p>\n<p><strong>Sertoli cell<\/strong><br \/>\ncell in seminiferous tubules that assists developing sperm and makes inhibin<\/p>\n<p><strong>testosterone<\/strong><br \/>\nreproductive hormone in men that assists in sperm production and promoting secondary sexual characteristics<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":90,"menu_order":74,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[],"license":[57],"class_list":["post-5163","chapter","type-chapter","status-publish","hentry","license-cc-by"],"part":5137,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapters\/5163","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/wp\/v2\/users\/90"}],"version-history":[{"count":1,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapters\/5163\/revisions"}],"predecessor-version":[{"id":5164,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapters\/5163\/revisions\/5164"}],"part":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/parts\/5137"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapters\/5163\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/wp\/v2\/media?parent=5163"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/pressbooks\/v2\/chapter-type?post=5163"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/wp\/v2\/contributor?post=5163"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/biology\/wp-json\/wp\/v2\/license?post=5163"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}