Endo 1: Repro Axis (overall and men) Flashcards
- Hypothalamus releases _________
- Anterior pituitary releases _________ (2)
- Gonads produce _______________ (3)
- Hypothalamus releases GnRH
- Anterior pituitary releases FSH, LH
- Gonads produce estradiol, progesterone, testosterone
What carbon has the hydrocarbon tail attached?
C17 has the carbon tail
What is the rate limiting step in gonadal hormone synthesis?
Conversion of cholesterol to pregnenalone
by 20-22 desmolase
What tissues have progesterone receptors? (3)
Uterus
Ovaries
Breast
What tissues have testosterone receptors? (5)
Testes
Bone and Muscle (growth)
Skin
Brain (libido)
What is the function of aromatase?
Aromatase converts
(1) testosterone to estradiol
(2) androstenedione to estrone
What is the function of 5 alpha reductase?
Conversion of testosterone to DHT
What is the source of cholesterol in theca cells?
Granulosa cells?
Theca: uptake LDL from bloodstream
Granulosa: synthesize cholesterol de novo
What hormones are made by theca and granulosa cells?
Theca: progesterone and testosterone
Granulosa: progesterone and estradiol
What is the interaction between theca and granulosa cells in hormone synthesis?
- Granulosa and theca cells makes progesterone
- Granulosa’s progesterone migrates to theca cell
- Theca cell makes testosterone from progesterone
- Testosterone migrates back to granulosa cell and gets converted into estradiol
Compare the receptors found on Sertoli cells, Leydig cells, and Granulosa cells
- Sertoli cell only has FSH receptor
- Leydig cell only has LH receptor
- Granulosa cell has both FSH and LH receptor
Compare the time-dependence of these hormone synthesis pathways in men and women
Men: all pathways are regulated together (either all active or all inactive)
Female: relative activity of different pathways depends on phase in cycle
What structure releases GnRH?
Be specific.
Preoptic nucleus of hypothalamus
Where is HcG made?
HcG is made by placenta
Compare the structure of FSH, LH, TSH, HcG?
All peptide hormones with the same alpha subunit
How does GnRH release change with age?
- GnRH is released at a low, steady level before puberty
- GnRH is released in pulsatile manner in reproductive men and women
Name the intermediates between cholesterol and testosterone (6)
- Cholesterol
- Pregnenalone
- 17 alpha hydroxy pregnenalone
- DHEA
- androstenedione or androstenediol
- Testosterone
What is the effect of continuous GnRH release?
B/c GnRH is normally released in a pulsatile manner, continuous release will shut the system off
What is the function of 20-22 desmolase?
Converts cholesterol into pregnenalone
*Rate limiting step
What enzyme converts testosterone to DHT?
What enzyme converts testosterone to estradiol?
5 alpha reductase makes DHT from testosterone
Aromatase mades estradiol from testosterone
What is estradiol and estrone made from?
Testosterone
What hormone do Leydig cells respond to?
What do Leydig cells make?
Leydig cells
- respond to LH
- make testosterone
What hormone do Sertoli cells respond to?
What do Sertoli cells make?
Sertoli cells
- respond to FSH
- Make ABP, inhibin, aromatase
What is the interaction between Leydig cells and Sertoli cells in hormone synthesis?
- Leydig cells make testosterone
- Testosterone migrates to Sertoli cell
- Sertoli cells make aromatase, which converts testosterone into estradiol
- Sertoli cells also make ABP, which binds testosterone
What is the negative feedback pathway for sex hormones in men?
- Testosterone (made by Leydig cells) inhibits anterior pituitary and hypothalamus
- Inhibin (made by Sertoli cells) inhibits anterior pituitary only
Do Sertoli cells or Leydig cells promote spermatogenesis?
Sertoli cells promote spermatogenesis
