Reproductive Hormones Flashcards
What is the result of GnRh release from the hypothalamus?
Cause gonadotrophs to release FSH and LH
What happens with sustained GnRH?
Inhibit FSH/LH release
What is the half life of GnRH?
degraded by peptidases in about 4 min.
What inhibits GnRH?
Negative feedback from sex steroids and GnIH
What does LH do in females?
Released in a pulsitive manner and stimulates production of corpus luteum
What is the targets for LH?
Females: Theca cells
Males: Leydig cells
What is the main cause of ovulation?
Large increases in LH
What inhibits LH?
Sustained release of GnRH and negative feedback from sex steroids
What is the structure of LH and where is it made?
Alpha and beta chains and made by gonadotrophs in the pituitary
What does FSH do in females?
Stimulate the growth of Graafian follicles
What is the structure and where is FSH made?
Alpha and Beta chain made by gonadotrophs in the anterior pituitary
What activates FSH?
GnRH released in a pulsative manner and activin
What inhibits FSH?
Sustained release of GnRH and inhibin and negative feedback
What is the half life of FSH?
30-100 minutes
What is the targets of FSH?
Females: granulosa cells
Males: Sertoli cells
What is prolactin?
Protein hormone made in the anterior pituitary by lactotrophs. Similar to growth hormone
What does prolactin do in females?
- Mammogenesis
- Lactogenesis
- Galactopoeisis
- Repro and body effects
What does prolactin do in males?
Sensitize leydig cells to LH potentiating testosterone
What regulates prolactin?
Negatively regulated by dopaminergic neurons in the arcuate nucleus
What is oxytocin?
Peptide hormone made in the hypothalamus and released in the posterior pituitary
What does Oxytocin do in females>
- Smooth muscle contraction in repro organs
- Prostaglandin synthesis
- CNS effects
What does Oxytocin in males?
Contraction of the epididymis and vas deferens and prostaglandin synthesis
What regulates oxytocin?
Neural sensory pathways and positive feedback loop
What is melatonin?
Monoamine hormone made by pineal gland at nigh
What is the purpose of melatonin?
Functions in circadian rhythm and core for seasonal breeders through the KISS system controlling GnRH and direct stimulation of pars tuberalis
What is the effect of melatonin on KISS neurons in short day breeders?
Inhibits
What is the effect of melatonin on KISS neurons in long day breeders?
Stimulates
What does 17B- hydroxysteroid dehydrogenase do?
Synthesize testosterone or estradiol from weaker androgens or estrogens
What does Aromatase do>
Needed for synthesis of all estrogens
What does 5a-reductase do?
Needed for synthesis of Dihydrotestosterone
WHere is testosterone produced?
C19 androgen steroid made in leydig cells in testis (small amount in the adrenal glands and ovaries)
How is testosterone made?
Reduced from adrostenedione by 17bHSD and controlled by LH
What is the half life of testosterone?
30-40min
What are the carrier proteins for testosterone?
SHBG and ABP
What is dihydrotestosterone?
C19 hormone made by reducing testosterone with 5a-reductase
What androgen is more potent?
DHT
What is the half life of DHT?
50-60min
Why are circulating levels of DHT low?
Usually made at the site of action
What is estradiol?
C18 estrogen made from androtenedione with 17b-HSD and aromatase
Where is aromatase found?
Males: sertoli cells
Females: Granulosa cells
What are non repro effects of estradiol?
- Bone maintenance
- Closure of epiphyseal plate (why women are usually shorter)
What is the carrier protein for estradiol?
SHBG
What is the strongest estrogen?
Estradiol
What are other estrogens?
Estrone, estriol, and equilin
What receptors do estrogens bind to?
Estrogen receptors but some differentiate to cause different effects on different tissues
What is progesterone?
C21 progestin secreted by granulosa luteal cells in CL during luteal phase of estrous
What is the effect of progesterone?
-pro-gestational (pause estrous cycle during pregnancy and support pregnancy)
What receptors do progesterones bind to?
- Nuclear progesterone receptors
- Membrane receptor
How is progesterone made?
Is an intermediate in almost all steroid making tissues. Only secreted in absence of advanced steroid enzymes
What is the structure of activins?
dimers of inhibin beta subunits
What is the structure of inhibins?
dimers of alpha and beta subunit
What receptor do inhibins/activins bind to?
Activin receptors
What cells secrete activin and inhibins?
Males: Sertoli
Female: granulosa cells
What regulates activin/inhibin?
Follistatin. Binds to activin to prevent activin binding
What is the role of prostaglandins in the male repro tract?
- regulate immune response to sperm in males and females
- regulate activity of ductal system
What is the role of prostaglandins in females?
- Contractions
- Control luteolysis
- signaling for sperm
What is hCG and eCG(PMSG)
produced by placenta in humans and horses respectively (LH receptor agonists)
