Hormonal Regulation in Male Reproduction
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Questions and Answers

What initiates the secretion of FSH and LH at puberty?

  • Increased secretion of GnRH (correct)
  • Decrease in testosterone levels
  • Suppression of Sertoli cell activity
  • Increase in inhibin levels

    • Which hormone primarily stimulates Leydig cells to produce testosterone?

  • FSH
  • GnRH
  • LH (correct)
  • Inhibin

    • What role does FSH play in spermatogenesis?

  • Stimulates Leydig cells to secrete testosterone
  • Suppresses testosterone secretion
  • Inhibits production of androgen-binding protein
  • Acts on Sertoli cells to promote spermatogenesis (correct)

    • What is the function of androgen-binding protein (ABP) in the testes?

    <p>Binds testosterone to maintain high concentrations</p> Signup and view all the answers

    How does the negative feedback mechanism control testosterone production?

    <p>High testosterone levels inhibit GnRH secretion</p> Signup and view all the answers

    What is the most common disorder associated with primary congenital male hypogonadism?

    <p>Klinefelter’s syndrome (47XXY)</p> Signup and view all the answers

    Which condition is classified as a secondary cause of male hypogonadism?

    <p>Hypothalamic tumors</p> Signup and view all the answers

    What triggers Sertoli cells to release inhibin?

    <p>High sperm production</p> Signup and view all the answers

    What is the primary role of testosterone in spermatogenesis?

    <p>Facilitates the final stages of sperm maturation</p> Signup and view all the answers

    What happens to blood testosterone levels when they become excessively high?

    <p>GnRH secretion is inhibited by the hypothalamus</p> Signup and view all the answers

    What effect do high levels of oestrogen have on the release of GnRH, LH, and FSH?

    <p>They stimulate GnRH, LH, and FSH release.</p> Signup and view all the answers

    What hormonal changes occur after the formation of the corpus albicans?

    <p>Low levels of oestrogen and progesterone promote GnRH, LH, and FSH release.</p> Signup and view all the answers

    Which is one of the primary actions of oestrogen in the hormonal birth control context?

    <p>It inhibits the release of FSH.</p> Signup and view all the answers

    How does progesterone function in hormonal birth control?

    <p>It prevents LH release to inhibit ovulation.</p> Signup and view all the answers

    Which phase is primarily associated with low levels of oestrogen and progesterone?

    <p>Menstrual phase</p> Signup and view all the answers

    What hormonal feedback effect occurs during the pre-ovulatory phase?

    <p>Moderate oestrogen levels inhibit GnRH, LH, and FSH.</p> Signup and view all the answers

    What is the primary purpose of the combined pill in hormonal birth control?

    <p>To create an environment unsuitable for sperm.</p> Signup and view all the answers

    What is one consequence of high levels of oestrogen during the menstrual cycle?

    <p>It stimulates the release of GnRH, LH, and FSH.</p> Signup and view all the answers

    What effect does the progesterone-only pill have on the menstrual cycle?

    <p>It makes cervical mucus non-conducive to sperm.</p> Signup and view all the answers

    What is the primary hormone secreted by Leydig cells found in the testes?

    <p>Testosterone</p> Signup and view all the answers

    Which statement accurately describes the function of Sertoli cells?

    <p>They form the blood-testis barrier.</p> Signup and view all the answers

    Which hormone is primarily responsible for the regulation of spermatogenesis alongside testosterone?

    <p>Follicle stimulating hormone</p> Signup and view all the answers

    What role does inhibin play in male reproductive physiology?

    <p>Inhibits the production of follicle stimulating hormone.</p> Signup and view all the answers

    Which hormone is known as interstitial cell-stimulating hormone (ICSH) in males?

    <p>Luteinising hormone</p> Signup and view all the answers

    What is the function of 5 alpha-reductase in the male reproductive system?

    <p>It converts testosterone into dihydrotestosterone.</p> Signup and view all the answers

    Which of the following hormones is NOT involved in the hormonal regulation of the male reproductive system?

    <p>Human chorionic gonadotropin</p> Signup and view all the answers

    Which of the following is a function of FSH in the male reproductive system?

    <p>Promotes the development of spermatocytes during spermatogenesis.</p> Signup and view all the answers

    What is the primary mechanism by which levonorgestrel inhibits ovulation?

    <p>It inhibits the release of GnRH.</p> Signup and view all the answers

    During which stage of gestation does the process of organogenesis primarily occur?

    <p>17 - 60 days</p> Signup and view all the answers

    Thalidomide, when used during pregnancy, is particularly associated with which of the following effects on the fetus?

    <p>Phocomelia and heart defects</p> Signup and view all the answers

    Which teratogenic drug is characterized by its role as a vitamin K antagonist?

    <p>Warfarin</p> Signup and view all the answers

    Systemic use of aminoglycosides during pregnancy is primarily associated with which outcome for the fetus?

    <p>Deafness</p> Signup and view all the answers

    Which drug is known to cause vaginal adenosis in female foetuses when administered during pregnancy?

    <p>Stilbestrol (Diethylstilbestrol)</p> Signup and view all the answers

    What is a significant effect of retinoids such as etretinate when exposure occurs during pregnancy?

    <p>Hydrocephalus</p> Signup and view all the answers

    What is the primary role of follicle-stimulating hormone (FSH) in the female reproductive cycle?

    <p>Stimulates ovarian follicles to secrete estrogens</p> Signup and view all the answers

    Which of the following treatments is an antiandrogen used in prostate cancer therapy?

    <p>Flutamide</p> Signup and view all the answers

    What mechanism does sildenafil utilize to treat erectile dysfunction?

    <p>Increasing cGMP levels</p> Signup and view all the answers

    What hormone is primarily secreted by the corpus luteum to prepare the endometrium for implantation?

    <p>Progesterone</p> Signup and view all the answers

    What is the consequence of GnRH release inhibition by ovarian hormones?

    <p>Inhibition of FSH and LH secretion</p> Signup and view all the answers

    Which hormone is responsible for inducing relaxation of the uterus during pregnancy?

    <p>Relaxin</p> Signup and view all the answers

    What common condition affects one-third of males over age 60 related to the prostate?

    <p>Benign prostatic hyperplasia</p> Signup and view all the answers

    What hormonal change triggers ovulation in the menstrual cycle?

    <p>A surge in luteinizing hormone (LH)</p> Signup and view all the answers

    What best describes the role of inhibin in the female reproductive system?

    <p>Inhibits secretion of FSH and LH</p> Signup and view all the answers

    What is a primary characteristic of benign prostatic hyperplasia?

    <p>Sensation of incomplete emptying</p> Signup and view all the answers

    Which event occurs during the pre-ovulatory phase of the menstrual cycle?

    <p>Repair of the endometrium due to oestrogens</p> Signup and view all the answers

    What triggers the release of GnRH during the post-ovulatory phase when fertilization does not occur?

    <p>Degeneration of the corpus luteum</p> Signup and view all the answers

    Which medication is known to prevent estrogen production and is used in the treatment of endometriosis?

    <p>Danazol</p> Signup and view all the answers

    What is the primary consequence of high oestrogen levels prior to ovulation?

    <p>Positive feedback leading to increased LH secretion</p> Signup and view all the answers

    Which treatment option has been linked to an increased risk of endometrial cancer among women using hormone replacement therapy?

    <p>Combined therapy with estrogen and progesterone</p> Signup and view all the answers

    Which hormonal level change occurs during the transition from the post-ovulatory phase to menstruation?

    <p>Decrease in both oestrogen and progesterone</p> Signup and view all the answers

    What effect does combined hormonal contraceptive have on follicle development?

    <p>Inhibits FSH and prevents further follicle development</p> Signup and view all the answers

    What is the role of low oestrogen levels after the corpus albicans is formed?

    <p>Promotes the release of GnRH, LH, and FSH</p> Signup and view all the answers

    How does progesterone function within the combined pill context?

    <p>Inhibits LH release to prevent ovulation</p> Signup and view all the answers

    What feedback effect predominates during the pre-ovulatory phase of the menstrual cycle?

    <p>Positive feedback stimulating GnRH release</p> Signup and view all the answers

    Which aspect of hormonal birth control aims to make the endometrium unsuitable for implantation?

    <p>Administration of both oestrogen and progesterone</p> Signup and view all the answers

    Which physiological changes occur during ovulation as a result of hormonal signals?

    <p>Surge in LH due to high levels of oestrogen</p> Signup and view all the answers

    What is the primary hormone responsible for stimulating ovulation in the female reproductive cycle?

    <p>Luteinizing hormone (LH)</p> Signup and view all the answers

    Which hormone functions to relax the uterus during pregnancy by inhibiting contractions of the myometrium?

    <p>Relaxin</p> Signup and view all the answers

    Which condition is classified as a teratogenic effect observed when certain drugs are used during pregnancy?

    <p>Vaginal adenosis in female fetuses</p> Signup and view all the answers

    In the female reproductive cycle, what triggers the surge in LH that leads to ovulation?

    <p>Increase in estrogen levels</p> Signup and view all the answers

    What hormonal change occurs after the corpus luteum forms post-ovulation?

    <p>Decreased levels of FSH and LH</p> Signup and view all the answers

    Which mechanism describes how hormonal birth control primarily functions to prevent ovulation?

    <p>Inhibition of ovary stimulation by GnRH</p> Signup and view all the answers

    What excess hormone is associated with negative feedback that inhibits the release of GnRH, LH, and FSH?

    <p>Estrogens</p> Signup and view all the answers

    What condition is commonly seen in males over 60 years old that relates to the prostate?

    <p>Benign prostatic hyperplasia</p> Signup and view all the answers

    How does sildenafil treat erectile dysfunction through its physiological mechanism?

    <p>Inhibits phosphodiesterase type V (PDE5)</p> Signup and view all the answers

    Study Notes

    Reproductive Endocrinology

    • Recommended Reading:
      • Rang and Dales Pharmacology - Chapter 34
      • Tortora and Derrickson's Anatomy and Physiology - Chapter 28
    • Practice MCQ questions: Available on Moodle.
    • Topics to cover:
      • Hormonal regulation of the male reproductive system
      • Hormonal regulation of the female reproductive system
      • Contraceptive pill
      • Reproductive pathology and treatment
      • Pregnancy/birth/lactation
      • Teratogens

    Male Reproductive System

    • Cells of the testes:

      • Leydig cells: located between seminiferous tubules, secrete testosterone.
      • Sertoli cells: embedded in the tubules, form the blood-testis barrier, nourish spermatocytes, mediate testosterone/FSH effects on spermatogenesis, phagocytose excess spermatids, and secrete inhibin.

    • Hormone control of Spermatogenesis:

      • GnRH (gonadotrophin-releasing hormone): controls the release of FSH and LH, its release is inhibited by high testosterone levels.
      • FSH (follicle-stimulating hormone): stimulates spermatogenesis.
      • LH (luteinising hormone): stimulates testosterone secretion (also called interstitial cell-stimulating hormone (ICSH)).
      • Testosterone and DHT (dihydrotestosterone): essential for spermatogenesis, development of external genitalia, and prostate function. 5-alpha-reductase converts testosterone to DHT.

    • Inhibin: regulates sperm production by inhibiting FSH.

    • Control of Testosterone Production:

      • Negative feedback system regulates testosterone levels.
      • Hypothalamus receptors detect increased testosterone levels. This inhibits GnRH secretion
      • Reduced LH secretion from the anterior pituitary.
      • Leydig cells produce less testosterone, returning blood levels to normal.

    • Male Hypogonadism:

      • Primary congenital: Testicular agenesis (failure to develop), Klinefelter's syndrome (47XXY).
      • Primary acquired: Bilateral orchitis (inflammation of testes), mumps, irradiation, or cytotoxic drugs.
      • Secondary: Pituitary disorders, hypothalamic disorders (e.g., Kallman's syndrome — GnRH deficiency).

    • Aging in the male reproductive system:

      • Enlargement of prostate (benign hyperplasia): common in men over 60. Symptoms include frequent urination, decreased force of stream, bed wetting, and sensation of incomplete emptying.

    • Prostate Cancer:

      • Leading cause of male cancer death.
      • Blood test for prostate-specific antigen (PSA).
      • Antiandrogens (e.g., flutamide or cyproterone) used in treatment to block testosterone/DHT actions, preventing prostate cancer cell growth.

    • Erectile Dysfunction (Treatment):

      • Viagra (Sildenafil citrate) – PDE5 inhibitor.
      • Nitric oxide (NO) released by nerves diffuses into smooth muscle cells. Activates guanylate cyclase, increasing cGMP. cGMP activates protein kinase G, reduces [Ca2+], leading to vasodilation, and increased blood flow to the penis. Sildenafil is a selective inhibitor of PDE5.

    Female Reproductive System

    • The Female Reproductive Cycle:

      • Ovarian cycle: cyclic changes in ovaries, including the maturation of oocytes.
      • Uterine (menstrual) cycle: concurrent changes in the uterine endometrium to prepare for fertilization.

    • Hormonal control (female):

      • GnRH (gonadotropin-releasing hormone): secreted by hypothalamus, stimulates FSH and LH release from anterior pituitary. Its release is continuous but may be pulsatile.
      • FSH (follicle-stimulating hormone): initiates follicular growth, stimulates ovarian follicles to secrete estrogens.
      • LH (luteinising hormone): stimulates further ovarian follicle development, triggers ovulation, promotes corpus luteum formation, and produces estrogens, progesterone, relaxin and inhibin.
      • Estrogens: main estrogen is β-estradiol. Promotes female reproductive structures and secondary sex characteristics, increases protein anabolism (bone building), lowers blood cholesterol and inhibits GnRH, LH and FSH release.
      • Progesterone: primarily secreted by corpus luteum. Works with estrogens to prepare and maintain endometrium for implantation and mammary glands for milk production. Inhibits GnRH and LH secretion.
      • Relaxin: produced by corpus luteum. Relaxes uterus during pregnancy, increasing pubic symphysis and uterine cervix flexibility.
      • Inhibin: secreted by granulosa cells. Inhibits FSH and LH secretion.

    • Phases of the female reproductive cycle:

      • Menstrual phase
      • Pre-ovulatory phase (follicular stage)
      • Ovulation
      • Post-ovulatory phase (luteal phase)

    • Corpus luteum:

      • If oocyte is not fertilized, the corpus luteum degenerates into corpus albicans reducing progesterone and estrogen levels, initiating menstruation.
      • If oocyte is fertilized, the corpus luteum produces high levels of progesterone and estrogen to support pregnancy. Human chorionic gonadotropin (hCG) produced by the embryo maintains corpus luteum function during early pregnancy.

    • Hormonal interactions:

      • Levels of estrogen and progesterone fluctuate throughout the cycle. These fluctuations initiate negative and positive feedback mechanisms, regulating GnRH, LH and FSH release and ovulation.

    • Causes of female hypogonadism:

      • Primary congenital: problems in the ovaries, including Turner's or Noonan's syndromes.
      • Primary acquired: damage to ovaries (e.g., chemotherapy, irradiation).
      • Secondary: problems that stem from pituitary or hypothalamic disorders.

    • Aging in the female reproductive system:

      • Menopause is associated with several symptoms: hot flashes, copious sweating, headache, vaginal dryness, depression, weight gain, and emotional fluctuations.

    • Endometriosis:

      • Growth of endometrial tissue outside of the uterus.

    • Breast Cancer:

      • Common cause of cancer in women
      • Two genes increase susceptibility to breast cancer (BRCA1, BRCA2).
      • Mutations of BRCA1 and BRCA2 also increase risk of ovarian cancer.
      • Treatment involves hormone therapy, surgery (lumpectomy or mastectomy) radiation treatment, and chemotherapy.

    • Hormonal birth control:

    • Combined Pill: Oestrogen and progesterone inhibit FSH and follicle development. Progesterone prevents ovulation and makes cervical mucus inhospitable to sperm, and together they make the endometrium less receptive to implantation.

      • Progesterone-only Pill: Levonorgestrel. Makes cervical mucus inhospitable to sperm, inhibits ovulation (by downregulating LH release).
      • Morning-after Pill: Effective in preventing pregnancy if taken within 72 hours of unprotected intercourse.

    • Teratogens:

      • Agents that cause birth defects.
      • Include chemicals, drugs, cigarette smoking, and irradiation.
      • Teratogens affect different processes depending on the stage of fetal development.

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    Lect 16 Reproduction Endocrinology PDF

    Description

    Explore the intricate hormonal mechanisms that govern male reproduction, including the roles of FSH, LH, and testosterone. This quiz covers topics such as spermatogenesis, feedback mechanisms, and the impact of hormonal changes on reproductive health.

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