Reproductive Endocrinology Flashcards
(78 cards)
Explain the synthesis of sex hormones.
- Cholesterol
- Pregnenolone -> Progesterone
- Other steps
- Androstenedione -> estrone (CYP19) and testosterone (17beta-HSD)
- Testosterone -> estradiol (Aromatase/ CYP19)
- Testosterone -> Dihydrotestosterone (5alpha-reductase)
Carnegie Stages
System used by embryologists to describe the apparent maturity of embryos (Embryonic, E)
Postovulatory Age
- Frequently used by clinicians to describe the maturity of an embryo
- Refers to the length of time since the last ovulation before pregnancy (days, d)
Gonadal Ridge
- Bipotential gonad
- First thing to differentiate
Rspo1
- XX
- Wnt4/beta-catenin
- Female gene development: Mullerian duct (uterine tube)
- Reduction of Wolffian duct
Sry
- XY
- Sox9
- Testosterone and Anti Mullerian hormone (AMH)
- AMH represses female gonadal development
- Wolffian duct development (vas deferens)
What are the components of male genitalia?
- 2 testes
- 2 ductus deferens
- Accessory sex glands (prostate, seminal vesicles, etc.)
- Pelvic/penile urethra
- Penis
- Seminal vesicle is testosterone tissue
What are the components of female genitalia?
- 2 ovaries
- 2 uterine tube/oviduct
- Uterus
- Cervix
- Vagina
Explain the process of sexual differentiation of the brain.
- Androgens produced by fetal and neonatal testes are converted to estradiol in the brain by aromatase
Bovine Twins
- Female (XX): does not have reproductive anatomy (infertile)
- Freemartin
Dichlorodiphenyltrichloroethane (DDT)
- Androgen receptor antagonist (DDE) (can also bind to estrogen receptor beta) -> not activated (poor or no differentiation in tissues)
- Endocrine disruptor
Explain the HPG axis basics.
- Hypothalamus: Gonadotropin releasing hormone (GnRH)
- Anterior Pituitary Gland: Luteinizing Hormone/ Follicle Stimulating Hormone (LH/FSH)
- LH -> endocrine cells -> steroid and peptide hormones
- FSH -> gamete production
Oxytocin
- Effects: milk ejection, uterine smooth muscle contraction, maternal behavior
- Positive control: physical stimulation (teat/nipple/cervical) and psychological (visual/auditory)
- Negative control: catecholamines (stress)
Explain GnRH neuron input.
- Kisspeptin neuron -> GnRH neuron (releases GnRH)
- GnRH neurons do not express steroid R
Inhibin
- Blocks FSH production
- Androgens stimulate inhibin
- Gonadal inhibin: decreases FSH production by blocking action of activins
Activin
- Supports LH (activin A) or FSH (activin B) production
- Follistatin binds to activin and prevents it from increasing FSH
Explain the male HPG axis.
- Hypothalamus: secretes GnRH
- GnRH in hypothalamo-pituitary portal vessels
- Anterior pituitary: secretes FSH and LH
- FSH -> Sertoli cells in testes -> stimulate spermatogenesis and inhibin
- LH -> Leydig cells -> testosterone -> Reproductive tract and other organs
- Inhibin -> negative feedback to anterior pituitary (only FSH)
- Testosterone -> negative feedback to hypothalamus and anterior pituitary (only LH)
Explain the female HPG axis.
- Hypothalamus: secretes GnRH
- GnRH in hypothalamo-pituitary portal vessels
- Anterior pituitary: secretes FSH and LH
- FSH -> Granulosa cells in ovaries -> influence oocytes, secrete inhibin, and convert androgens to estrogen
- LH -> Theca cells -> androgens
- Inhibin -> negative feedback to anterior pituitary (primarily FSH)
- Estrogen -> positive feedback to anterior pituitary and hypothalamus
Where is testosterone produced in males?
Interstitial space (Leydig cells)
What types of cells are found in the seminiferous tubules?
- Germ cells (spermatogonia)
- Sustentacular (Sertoli cells): produce inhibin
Leydig Cells
- Interstitial space (between seminiferous tubules)
- Respond to LH to secrete testosterone (feedback to brain to decrease GnRH and LH
- Indirectly support spermatogenesis by producing testosterone
- Rich in steroidogenic enzymes necessary for steroidogenesis (testosterone production)
Sertoli Cells
- Support germ cells
- Secrete inhibins (feedback to brain to decrease FSH)
- Respond to FSH
- In fetal life, secrete AMH
- Form tight junctions (blood testis barrier)
What are the roles of testosterone?
- Stimulate spermatogenesis
- Maintain Wolffian duct, accessory glands
- External genitalia, secondary sex characteristics
- Simulate metabolism (muscle growth)
- Affect CNS function/behavior
Cryptorchidism
- Undescended testes
- Most common birth defect of male genitalia
- Will not produce normal sperm but will produce androgens
- Increased risk of testicular cancer
- Caused by hormonal abnormalities, genetic or environmental changes