Reproductive Endocrinology 9/8/15 Flashcards
What structures secrete sex steroids?
Adrenal cortex, the placenta, and the gonads.
What are the 3 major classes of sex steroids?
Pregnanes (21 C’s)
Androgens (19 C’s)
Estrongens (18 C’s)
The primary male hormone is _____ which is a ________.
Testosterone, androgen
The primary female hormones are ______ and _______.
Progesterone and Estradiol
______ can serve as a precursor for other steroids.
Progesterone
Synthesis and secretion of sex steroids are controlled by what?
The neuroendocrine system, HPG axis = hypothalamus, Ant. pituitary gland and gonads.
*Cannot be stored in vesicles b/c they are lipophilic!
Describe the secretion of GnRH….
Secreted from the hypothalamus
- Pulsatile secretion due to pacemaker neurons that produce AP’s.
Describe the secretion of LH and FSH…..
Secreted from the Ant. Pituitary gland.
- Pulsatile secretion in response to burst of GnRH from the hypothalamus.
Secretion of LH and FSH stimulates __________.
pulsatile secretion of gonadal steroids
What does continuous, non pulsatile GnRH secretion do?
Down regulates GnRH receptors in the Ant. Pituitary and inhibits LH and FSH secretion.
What do gonadal steroids regulate?
- Gametogenesis
- Hormone synthesis
- Regulate protein synthesis in other reproductive organs
What are the 3 types of cells in the testis with important reproductive functions?
- Spermatic cells
- Leydig cells or interstitial cells
- Sertoli cells
What do sertoli cells do? (3 things)
- Regulate spermatogenesis and produce hormone Inhibin in response to FSH.
- Inhbin has negative feedback actions on FSH secretion.
- produce androgen binding protein that helps sequester T in the testis
- Secretes tubular fluid to provide nutrients form spermatozoa.
What do Leydig cells do?
- Synthesize T in response to LH.
What do Spermatic cells do?
They are mitotically native spermatogonia and spermatocytes that mode through the walls of the seminiferous tables from the basal lamina towards the apical surface/lumen as they mature.
In the periphery, T is often converted to __________ by _______.
DHT by 5alpha-reductase
*DHT is potent androgen
_____ can be used to treat hair loss.
5-alpha reductase inhibitors!
*DHT promotes male pattern hair loss.
_____ Inactivates hair follicles.
DHT
_____ is important for sexual differentiation, development and maintenance of secondary sex characteristics, lbido and sexual behavior.
Testosterone
What effects of T are important for females?
- stimulates muscle growth and erythropoiesis
What is andropause?
male counterpart to menopause, its far less dramatic b/c there are no physiological changes.
- emotional disorders associated
- decrease in sperm count
- no cessation of fertility
What are the 4 cells types of the ovary?
- Oocytes = future egg enclosed in a ball of cells called an ovarian follicle.
- Theca cells = surround each follicle (location and function is analogous to Leydig cells)
- Granulosa cells = are epithelial cells of the follicle (analogous to sertoli cells) In early follicle, one or more layers of cells surround the oocyte. Continue to surround the oocyte in the cumulus oophorus…
- Luteal cells = are present after ovulation when the theca and granolas cells from he ovulatory follicle are transformed into the cells of the corpus luteum.
Theca cells synthesize _______ in response to _______.
Androstenedione in response to LH
Androstenedione diffuses into _______.
Granulosa cells
What do granulosa cells do in response to FSH?
- Convert androstenedione to estrone which is converted to estradiol
What does estradiol do? (6 things)
- stimulates granulosa cell function and replication
- regulates oocyte development
- regulates female secondary sex characteristics
- important regulator of bone turnover and arterial function
- typically inhibits GnRH and LH secretion
- Secretes inhibit that has negative feedback effect on FSH secretion.
Larger ovarian follicles have more LH and FSH receptors and will produce more Estradiol and inhibin, why is this important?
because these are all important factors regulating an ovarian cycle
What are the steps of an ovarian cycle?
1 and 2 = gonadotropin rise and follicular development
3-5 = increase estradiol (E2) and inhibit; dominant follicle selection
6-8 = FSH decrease, E2 peak, LH surge (positive feedback action of E2 on GnRH and LH)
9-11 = meiosis 1 completed, ovulation, CL formation
12-13 = increase E2 and P, inhibit gonadotropins
14-16 = CL regression, decrease steroids, gonadotropins rise.
*Menstrual cycle follows ovarian cycle
What are the phases of the Menstrual cycle?
Menstrual phase: begins when the Cl regresses and steroid support fir the uterine endometrium is lost.
Proliferative phase: follicular E2 stimulates proliferation of the endometrium
Follicular phase: ends with ovulation and CL formation
Luteal phase: P and E2 stimulate uterine secretory activity; increase glandular production of glycogen, increase angiogenesis, decrease contractility.
CL regresses (gonadotropin too low) and cycle begins again)
What causes menopause?
primarily due to ovarian failure loss of ovarian follicles due to atresia.
What are the hormone consequences of menopause?
- loss of ovarian steroids
- gonadotropin will be secretion very high
- increased reliance on adrenal steroids
Differentiation of Gonadal sex is determined by ____________.
the presence of a gene on the Y chromosome that encodes for SRY protein.
*SRY directs the indifferent gonad to become a testis
What 2 hormones regulate sexual differentiation of the internal genitalia?
Testosterone and Mullerian inhibiting substance (MIS)
*Both produced by fetal testis
In the undifferentiated state, there are two sets of tubules associated with the developing gonad, what are they?
Wolffian ducts and Mullerian Ducts
_______ duct system will become the tables associated with the male reproductive tract.
The wolffian ducts.
*T stimulates the proliferation of these ducts.
________ causes mullein duct system to regress.
MIS
What happens to Wolffian ducts in female?
Absence of T causes regression
What happens due to the lack of MIS in females?
Mullerian ducts will be maintained and become tables associated with female reproductive tract.
In the male ( in the present of androgen T), describe the final structures that result from:
- genital tubercle
- urogential fold
- labioscrotal folds
- genital tubercle = glans of the penis
- urogential fold = urethra and surrounding penis
- labioscrotal folds = scrotum and skin of penis
In the Female, (in the absence of androgens) describe the final structures that result from:
- genital tubercle
- urogential fold
- labioscrotal folds
- genital tubercle = glans of clitoris
- urogential fold = labia minor and urethral opening
- labioscrotal folds = labia majora
How is the brain sexually differentiated?
By the effects of T aromatized to E2 in the developing male.
What is congenital adrenal hyperplasia?
Adrenal enzyme deficiency results in excess production of adrenal androgens
- effects on Gonad and internal genitalia
- Genotype is XX
What results from a 5 alpha reductase deficiency?
Development of penis, scrotum and prostate gland is DHT dependent so there is a failure of differential of external genitalia early in life. However, increased T secretion with the onset of puberty will compete differentiation.
- Genotype is XY
- Phenotype is female at birth until early puberty
What is testicular feminization or androgen insensitivity?
Lack of functional androgen receptor (used by both T and DHT)
- No differentiation of genitalia
- Genotype is XY
- Phenotype is female
What happens during pregnancy?
There is a dramatic increase in circulating concentrations of steroid hormones during pregnancy due to placental production. - CL regress after 3 months and hCG supports luteal steroidogenesis.
- Placental E2 stimulates growth myometrium.
- Placental P reduces uterine contractility ans stimulates vasodilation.
What are some considerations for the pregnant dental patient?
More susceptible to gingivitis and periodontitis due to increased steroid hormones.
Medications and X-rays could effect fetus.
Comfort during exam or procedure.
