Reproductive Endocrinology Flashcards
What are the three sources of sex steroids?
- Adrenal cortex
- Placenta
- Gonads
What are the three major classes of sex steroids?
- Pregnanes (21C)
- Androgens/Androstanes (19C)
- Estrogens/estranes (18C)
The primary male hormone is ______ which is an ________.
testosterone; androgen
Testosterone is converted to the most potent androgen _____, by the enzyme 5alpha-reductase.
DHT
The two most important female hormones are ________ and _______.
progesterone; estradiol
Estradiol is an estrogen produced from _______ bu the enzyme aromatase.
testosterone
T/F: Sex steroids can be stored in the cell.
FALSE
Steroids are lipophilic hormones and cannot be stored
What is the reproductive axis?
Hypothalamus -> anterior pituitary -> Gonads
T/F: When stimulated, there is a constant flow of GnRH from the hypothalamus.
FALSE
Pulsating
Bursts of GnRH from the hypothalamus cause what response from the anterior pituitary?
Pulsating release of LH and FSH
If GnRH is received in the anterior pituitary in a constant fashion what will its response be?
Inhibit LH and FSH secretion
Gonadal steroids exert negative feedback control of GnRH and LH secretion, except in which case?
Estradiol has a positive feedback on LH prior to ovulation in females
In the gonads, which genes are transcribed by the steroid/receptor complex?
Genes regulating gametogenesis and hormone synthesis
What is a secondary effect of gonadal steroids?
Regulate protein synthesis in other reproductive organs (male accessory glands, uterus, breasts, brain)
Spermatic cells include _______ active spermatogonia and ______ spermatocytes.
mitotically; meiotic
________ cells synthesize testosterone in response to LH.
Leydig
Testosterone regulates sexual behavior after what?
After being aromatized to estradiol
What is the role of Sertoli cells?
Respond to FSH to regulate spermatogenesis and produce inhibin
_______ has negative feedback actions on FSH secretion.
Inhibin
What cells make up the epithelial lining of the seminiferous tubules?
Sertoli cells
In the testes, _______ cells respond to FSH; _______ cells respond to LH
Sertoli; Leydig
What are some effects of T that are important for women?
- Regulate bone growth
- Stimulate muscle growth
- Stimulate erythropoiesis
How is male pattern baldness treated?
5alpha-reductase inhibitors to decrease T -> DHT
DHT thought to be major contributor to baldness
T/F: As T decreases with age, most men become sterile.
FALSE
T does decrease, but most men remain fertile
______ cells surround each follicle and are similar in function to Leydig cells.
Theca
The _______ cells are the epithelial cells of the follicle.
Granulosa
_______ cells are present after ovulation, when the theca and granulosa cells are transformed into the cells of the corpus luteum.
Luteal
Theca cells respond to ___; while granulosa cells respond to ____.
LH; FSH
What hormone do Theca cells sythesize?
Androstenedione
Where does androstenedione go once synthesized?
Diffuses into granulosa cells and some into systemic circulation
What happens to androstendione in the granulosa cell?
Androstenedione -> estrone -> estradiol
What are the functions of estradiol secreted by the granulosa cells?
- Regulate oocyte development
- Regulate secondary sex characteristics
- Regulate bone turnover and arterial function
- Inhibits GnRH and LH secretion
Along with estradiol, what else is secreted by the granulosa cell?
Inhibin: negative feedback on FSH
Describe the ovarian cycle.
- Gonadotropin rise and follicle develops
- Increase E2 and inhibin
- FSH decrease (via inhibin increase); E2 peak -> LH surge
- Meiosis I complete, ovulation, CL formation
- Increase E2 and P -> inhibit LH and FSH
- CL regression, decrease steroids, LH/FSH rise
If pregnancy were to occur, the placenta produces ____.
hCG
What are the hormonal consequences of menopause?
- Lose ovarian steroids
- Gonadotropin and inhibin secretion very high
- Increase reliance on adrenal steroids
Which gene on the Y chromosome directs the indifferent gonad to become a testis?
SRY
What two hormones regulate sexual differentiation of the internal genitalia in males?
Testosterone and Mullerian inhibiting substance (MIS)
What are the roles of T and MIS in developing males?
T: stimulates Wolffian duct system which will become tubules of reproductive tract
MIS: causes Mullerian duct system to regress
What gonadal steroids are stimulated in the developing female?
None. Absence of T causes Wolffian duct to regress. Absence of MIS causes proliferation of Mullerian duct system.
What hormone stimulates male external genitalia differentiation?
Adrogens: T -> DHT
What would happen to a developing male with a 5alpha-reductase deficiency?
Less DHT would be developed during development -> no differentiation of external genitalia
Increased T at puberty would complete differentiation
Does Congenital adrenal hyperplasia cause problems in developing men or women?
Women. Not enough enzyme -> excess androgens.
Women will have male looking external genitalia
What is the result of an androgen insensitivity?
No functional androgen receptor -> T and DHT cannot function. Leads to XY genotype, but female phenotype
During pregnancy, placental ____ stimulates growth of myometrium, and ____ reduces uterine contractility and stimulates vasodilation.
E2; P
