E. Luteinizing hormone (LH) binds directly to LH receptors on the interstitial cells of Leydig (i.e. Leydig cells) to stimulate the production of testosterone. Low levels of LH result in decreased levels of testosterone, which can subsequently lead to decreased sperm production. Prolonged exposure to low levels of testosterone also leads to systemic effects including decreased muscle mass, lethargy, reduced libido, erectile dysfunction and infertility. Remember that LH acts directly on the Leydig cells to stimulate testosterone production and testosterone acts on the Sertoli cells to regulate spermatogenesis.
DHT is not associated with decreased muscle mass or lethargy. Effects of DHT on libido are unclear.
FSH does not regulate testosterone production. FSH is required by the Sertoli cells during the process of
spermatogenesis, but has no known effects on libido.
If given alone, prolactin could be a possible answer.
Hyperprolactinemia reduces GnRH secretion, leading to reduced levels of LH and FSH. In men, this can
result in low testosterone. Abnormal levels of prolactin are also associated with low libido and erectile
dysfunction. However, prolactin was paired with DHT and DHT is not the correct androgen, and therefore
this answer is not correct.
D. The temperature of the testes must be considerably below that of the internal body temperature for spermatogenesis to occur. The testes are normally maintained at a temperature of about 32°C (89.6°F) and are kept cool by a countercurrent heat exchange between the spermatic arteries and veins and by air circulating around the scrotum.
The testes develop in the abdomen, but normally descend into the scrotum during fetal and neonatal development.
In approximately 10% of newborn infants, one or, less commonly, both testes remain in the abdominal cavity or inguinal canal. Although most (98%) of undescended testes (cryptorchidism) spontaneously descend by 1 year, and all but 0.3% spontaneously descend by puberty, early surgical treatment is recommended because abdominal temperatures can
cause irreversible damage to the spermatogenic epithelium. Also, the incidence of malignant tumors is higher in undescended than in scrotal testes.
Maturation of spermatogonia, the primitive germ cells, into primary spermatocytes does not begin until adolescence. Throughout the reproductive life of the human male, 100 to 200 million sperms are produced daily. Of critical importance to the hormonal regulation of spermatogenesis is the pulsatile release of GnRH and the subsequent involvement of FSH and LH at their target cells.
FSH acts directly on the Sertoli cells of the seminiferous tubules to regulate mitotic and meiotic activity of germ cells.
LH effects are mediated via stimulation of testosterone secretion by the Leydig cells.
GnRH must be released in a pulsatile manner in order to stimulate FSH and LH secretion. Continuous release of GnRH results in down-regulation of GnRH receptors on gonadotropes and inhibition of FSH and LH synthesis and secretion.
D. Estrogen has a primary role in stimulating endometrial proliferation and regeneration after menses (D).
The direct effect of estrogen on the cervix (A) is to stimulate secretion of a thin, elastic, alkaline mucus. All of these effects facilitate enhanced sperm transport through the cervix.
Estrogen stimulates vaginal secretion of fluid with a high pH (B).
Estrogen helps to maintain bone density, by increasing osteoblast activity and decreasing osteoclast activity (C).
Growth of the breast alveoli and lobules is stimulated by progesterone; growth of the ductal elements is stimulated by estrogen (E).
Symptoms of estrogen deficiency include decreased bone density, decreased vaginal secretions and thus decreased vaginal lubrication and associated pain during sexual intercourse (dyspareunia). Estrogen deficiency is associated with problems at the level of the ovary (depletion of ovarian follicles in menopause, premature ovarian failure) or problems at the levels of the hypothalamus/pituitary leading to lack of follicle development and thus, reduced ovarian estrogen production (e.g. hypothalamic amenorrhea, excess prolactin secretion both of which inhibit GnRH and, thus LH and FSH release).
Symptoms of estrogen deficiency often accompany secondary amenorrhea and are most common in menopausal women, in premature ovarian failure (POF), in women who are underweight (anorexic, bulimic), in women who exercise a lot (hypothalamic amenorrhea), in women who are stressed (increased CRH decreases GnRH), and in women with excess prolactin secretion (excessively high prolactin levels inhibits GnRH).
E. The key piece of information provided in the stem of this question is the finding of galactorrhea on physical exam, which suggests this patient is suffering from hyperprolactinemia. Remember that women with hyperprolactinemia may present with oligomenorrhea or amenorrhea, complain of infertility, and may exhibit galactorrhea.
Recognize that high levels of prolactin suppress the release of GnRH (C), which subsequently reduces the circulating levels of LH and FSH (B, D), which leads
to reduced follicle recruitment/growth and lower levels of estradiol.
Estradiol stimulates breast development but does not in itself cause galactorrhea. GnRH, FSH and LH are likely reduced and the primary reason this woman is not experiencing normal menstrual cycles. The hyperprolactinemia is causing reduced secretion of GnRH and the galactorrhea.
Possible causes of hyperprolactinemia may include tumors (prolactinoma), reduced levels of dopamine (F) (which endogenously regulates the release of PRL), or increased secretion of thyrotropin releasing hormone (TRH) as in the case of hypothyroidism (low levels of thyroxine stimulate the hypothalamus to secrete increasing amounts of TRH and, at very high levels, TRH can stimulate PRL release).
The number of follicles recruited to enter the growing stage is dependent on the number of follicles left in the ovarian reserve. Like-wise, the number of antral follicles that are cyclically recruited into the cohort from which a dominant follicle will be selected depends on the number of preantral follicles available. Thus, a reduced number of follicles in the reserve means fewer follicles will be growing.
As women age, the number of growing follicles declines. Thus, estimating the number of growing follicles gives an indirect measurement of the number of follicles left in the ovarian reserve. Anti-müllerian hormone (AMH) (also known as müllerian inhibiting substance - MIS - the Sertoli cell hormone that is responsible for regression of müllerian ducts in males and thus responsible for the absence of female internal reproductive organs in males) is released from granulosa cells of growing follicles. Serum levels of AMH decline with age owing to loss of follicles from the reserve and an associated reduction in the number of growing follicles. Reduced AMH = reduced ovarian reserve.
Inhibin B is released from granulosa cells of antral follicles under FSH stimulation and the serum levels of inhibin B indicate the size of the cohort of follicles from which a dominant follicle will be selected. As the follicle pool declines, the number of follicles recruited during each menstrual cycle also declines. Thus, serum levels of inhibin B slowly decline with age and with deletion of the ovarian reserve.
Serum levels of FSH during the early follicular phase are controlled primarily by estrogen from the large antral follicles. Estrogen inhibits FSH in a negative feedback fashion. If follicles are not present or are of poor quality (as occurs as women progress towards menopause), estrogen is not produced in sufficient quantities to inhibit FSH secretion. Thus, FSH levels increase. In fact, increased early follicular phase (day 3 of menstrual cycle) FSH level is one of the earliest clinical markers of menopause. LH levels rise also (owing to reduced negative feedback from reduced estrogen and progesterone), but to a lesser extent.
Antral follicle count (AFC) or basal antral follicle count is another test for checking a females ovarian reserve. Antral follicles can be viewed by transvaginal ultrasound and counted. A count of ~13 antral follicles (diameter 2-10 mm) in the early follicular phase (Day 2-5 of the menstrual cycle) is considered normal and indicative of a sufficient ovarian reserve. Such a number would be expected in reproductive aged women with regular menstrual cycles. The number declines in relation to depletion of the ovarian reserve and is often < 4 antral follicles in women > 40 years. Increased number of antral follicles (>30) is indicative of PCOS
Ann, a 20-year-old female, visits her primary care physician complaining that she has never had a menstrual period. She is single and denies ever having had sexual intercourse. Physical examination shows normal breast development, but minimal axillary and pubic hair.
Which of the following represents the expected sequence of events in a physiologically normal pubertal female?
A. Adrenarche, Pubarche, Menarche, Thelarche,
B. Growth spurt, Pubarche, Thelarche, Menarche
C. Growth spurt, Thelarche, Pubarche, Menarche
D. Thelarche, Growth spurt, Pubarche, Menarche
E. Thelarche, Menarche, Pubarche, Growth spurt
F. Thelarche, Pubarche, Growth spurt, Menarche
7th EditionJulie S Snyder, Mariann M Harding 4th EditionDavid M Allan, Rachel Basco 1st EditionPaula Manuel Bostwick 13th EditionRebecca J. Donatelle