The Reproductive System Quiz

The Reproductive System

• The reproductive system is responsible for hormone production and maturation of germ cells in the gonads.
• Hypothalamus secretes GnRH (gonadotrophin-releasing hormone) which regulates the release of LH (luteinizing hormone) and FSH (follicle stimulating hormone) from the pituitary gland.
• Dopamine, a neurotransmitter, is also secreted by the hypothalamus and controls prolactin secretion.
• Pituitary gland secretes LH and FSH via basophil cells.
  • LH primarily stimulates hormone production in the gonads.
  • FSH stimulates the development of germ cells.
• Prolactin, secreted by pituitary acidophil cells, stimulates breast epithelial cell proliferation and induces milk production.
  • Prolactin secretion is inhibited by dopamine, unlike other pituitary hormones.
• Ovaries secrete estrogens, progesterone, and androgens.
  • Androgens (C19 steroids) are synthesized by theca cells and converted to estrogens (C18 steroids) in granulosa cells.
  • Oestradiol is the most important ovarian estrogen
  • Oestrogens are important for female secondary sex characteristics and menstruation.
  • Progesterone is secreted by the corpus luteum during the luteal phase of the menstrual cycle and during pregnancy.
    • It prepares the endometrium for a fertilized ovum.
    • It helps maintain early pregnancy.
    • It can cause a rise in basal body temperature.
• Testes secrete testosterone.
  • Testosterone is produced by Leydig cells and stimulated by LH.
  • Testosterone inhibits LH secretion through negative feedback.
  • Inhibin, produced by Sertoli cells, controls FSH secretion through negative feedback.
  • Testosterone is crucial for male sexual differentiation, secondary sex characteristics, spermatogenesis, and anabolism.
  • In target cells, testosterone is converted to dihydrotestosterone, a more potent androgen, by the enzyme 5-α-reductase.

Hyperprolactinaemia

• High plasma prolactin levels can lead to amenorrhea, sexual dysfunction, infertility, and potentially breast cancer.
• High prolactin levels inhibit GnRH release, reducing gonadotropin (LH and FSH) production and inhibiting gonadal hormone synthesis, resulting in infertility.
• Causes can be physiological (e.g., stress, pregnancy), hypothalamic (e.g., damage to pituitary stalk), pituitary tumors (microadenomas, macroadenomas), or drug-induced.

Hirsutism and Virilism

• Increased plasma free androgens or increased tissue sensitivity to androgens can lead to hirsutism (increased hair growth in male pattern) or virilism (masculinization).
• Testosterone is the main androgen.
• Causes of hirsutism include familial, PCOS, adrenal or ovarian tumors, Cushing’s syndrome, and exogenous androgens.
• Virilism features include increased male pattern hair growth, voice deepening, and breast atrophy.
• Common causes of virilism include adrenal or ovarian tumors, Cushing’s syndrome, and exogenous androgens.

Polycystic Ovary Syndrome (PCOS)

• PCOS is characterized by hyperandrogenism, anovulation, and abnormal ovarian morphology.
• It is the most common cause of anovulatory infertility.
• Symptoms include hirsutism, menstrual disturbances, enlarged polycystic ovaries, and infertility.
• Increased plasma testosterone and androstenedione levels are common.
• LH may be elevated, with normal FSH.
• Reduced SHBG levels can lead to increased free testosterone.
• Plasma prolactin levels may also be high.
• Ultrasound reveals multiple small subcapsular ovarian cysts.
• Associated with insulin resistance, obesity, elevated insulin levels, hyperlipidemia, glucose intolerance, and hypertension.

Infertility

• Primary infertility refers to a couple who have never conceived after a year of unprotected intercourse.
• Secondary infertility refers to a couple who have conceived previously but are unable to do so now.
• Even with a regular menstrual cycle, ovulation and luteal development should be evaluated.

Female Infertility Investigations

• Plasma progesterone levels during the luteal phase (day 21) can indicate ovulation.
  • Normal levels suggest ovulation.
  • Low levels (< 30 nmol/L) suggest ovulatory failure.
  • High levels (> 100 nmol/L) suggest pregnancy.
• Plasma FSH, LH, and estrogen levels can help determine the cause of infertility.
  • High FSH and LH with low estrogen indicate hypergonadotrophic hypogonadism (ovarian failure).
  • Low FSH, LH, and estrogen indicate hypogonadotrophic hypogonadism (pituitary or hypothalamic disease).
• A GnRH test can evaluate pituitary and hypothalamic function.
  • Normal response is a doubling of LH and FSH levels after injection.
  • Pituitary hypofunction is indicated by a lack of rise in LH and FSH.
  • An exaggerated response can indicate hypothalamic disease.
• Plasma prolactin levels should be checked to exclude hyperprolactinemia.
• Thyroid function tests should be conducted to rule out thyroid disease.
• Ovarian ultrasound can monitor follicular development and ovulation and exclude PCOS.
• Anti-Müllerian hormone (AMH) levels can assess ovarian reserve; low levels indicate poor reserve.

Male Infertility Investigations

• Semen analysis evaluates sperm count, motility, and morphology.
• Plasma testosterone, LH, and FSH levels should be measured.
  • High FSH and LH with low testosterone indicate hypergonadotrophic hypogonadism (testicular issues, like Leydig cell failure).
  • Low FSH, LH, and testosterone indicate hypogonadotrophic hypogonadism (pituitary or hypothalamic disease).
  • High FSH compared to LH may indicate seminiferous tubular failure (Sertoli cell failure).
• A GnRH test can evaluate pituitary and hypothalamic function as described above.
• Plasma prolactin levels should be checked to exclude hyperprolactinemia.
• Thyroid function tests should be conducted to rule out thyroid disease.
• A human chorionic gonadotrophin (hCG) stimulation test can assess Leydig cell reserve.
  • hCG shares a subunit with LH and stimulates Leydig cells to produce androgens.
  • It has a long half-life and can elevate plasma testosterone after 72-120 hours.