Progestins, Estrogens & Androgens Flashcards
Describe the hypothalamic-pituitary-ovarian axis.
hypothalamus releases GnRH; pituitary stimulated to release FSH & LH; ovary stimulated for follicular growth and ovulation and to produce estrogens & progesterone; placenta binds to LH receptors to stimulate progesterone & estrogen production
progesterone vs estrogen for feedback
progesterone is inhibitory to hypothalamus
estrogen is inhibitory early in menstrual cycle but stimulatory midway through the cycle
**What does the ovary use in steroid synthesis that is not present in adrenal steroid synthesis?
aromatase (CYP19A1)
**theca vs granulosa cells
in ovary; theca cells are outside of the follicle (convert cholesterol to androgens); granulosa cells convert androgens to estrogens
What is the main estrogen in humans?
estradiol-17beta
actions of estrogens
stimulate growth & development of the mammary gland; promote endometrial proliferation during follicular phase; promote proliferation of vaginal epithelium; block resorption of bone; increase HDL; increase thromboembolism risk; increase endometrial/breast CA; *increase progesterone receptors
What is the most important progestin in humans?
progesterone
progesterone actions
endometrial development during luteal phase; determinant of onset of menstruation; *decreases cervical mucus and increases viscosity; increases basal body temp; stimulates development of mammary gland during pregnancy; maintenance of pregnancy
Which estrogen is most commonly used in contraceptives?
ethinyl estradiol
What is bisphenol?
BPA; environmental contaminant with esetrogen-like effects
non-hormonal contraception
copper IUDs
copper has spermicidal effect
*in theory it can prevent implantation…but in order for this to happen fertilization would have to have occurred prior to insertion of IUD
types of progestin contraceptive agents
oral daily
IM injections
SQ implants
IUDs
mechanism of action of progestins
- -prevent fertilization by decreasing the amt & increasing the viscosity of cervical mucus; prevent sperm from reaching uterus & fallopian tube
- -prevent ovulation by inhibiting gonadotropin secretion
Which drugs are typically combined in progestin/estrogen contraceptives?
norethindrone & ethinyl estradiol–*monophasic, biphasic, & triphasic preparations
–**drospirenone & ethinyl estradiol combo is Yaz
mechanism of action of progestin/estrogen combos
prevent ovulation by **inhibiting the hypothalamus & the pituitary; increase amt & viscosity of mucus
combo contraceptive adverse effects
avoid in pts w/ migraines; thromboembolism; MI in smokers; decreased glucose tolerance; weight gain; hirsutism
combo contraceptive health benefits
decreased ovarian cysts & benign fibrocystic breast disease; decreased endometrial & ovarian CA; increased HDL & decreased LDL levels
Which antibiotic reduces the efficacy of combo-type contraceptives? **
rifampins
mechanism of action of post-coital contraceptive
high dose of progestin; suppresses hypothalamic-pit-gonadal axis to inhibit ovulation
adverse effects of post-coital contraceptive
N/V; HA; dizziness; breast tenderness; abdominal and leg cramps
What is the hypothalamic-pituitary-testicular axis?
hypothalamus releases GnRH; signals pit to release LH & FSH; signals testes to release androgens (testosterone, dihydrotestosterone)
Why is 5alpha-reductace (SRD5A2) important?
in males; converts testosterone to dihydrotestosterone which is a better androgen
actions of androgens
virilization of urogenital tract during development; puberty; maintenance of secondary sex characteristics; spermatogenesis; anabolic reactions
