Endocrinology of the Male Reproductive Tract Flashcards
FSH targets the ___ cells
Sertoli
LH targets the __ cells
Leydig
Leydig cells produce:
testosterone
testosterone feedbacks at the gonadotroph cells to ____ the secretion of LH and FSH, and feedbacks at the hypothalamus to ___ the secretion of GnRH
decrease: LH FSH
decrease GnRH
Sertoli cells produce:
sperm
spermatogenesis depends on:
FSH and testosterone
another action of FSH acting on the Sertoli cell is the production of:
ABP (androgen binding protein)
ABP helps ensure:
a large concentration of testosterone within the seminiferous tubules
Sertoli cells make their own hormone, ____, which serves as ____
inhibin, a negative feedback signal for FSH, reduces their responsiveness to GnRH, and probably directly inhibits the release of GnRH
what accounts for the difference in the pulsatile rate of LH and FSH secretion?
testosterone changes the sensitivity of the cells producing LH
inhibin changes the sensitivity of the cells producing FSH
how do glycoprotein hormones from the pituitary work?
it results in the conversion of ATP to cAMP, cAMP activates protein kinases, phosphorylation cascade is going to convert cholesterol to testosterone and estradiol
in the blood, testosterone and estradiol mostly get bound up by ___. The rest is bound by ___. Only about __% isn’t bound up
sex steroid binding globulins, albumin and other plasma proteins, 3%
testosterone has a __ negative feedback effect on FSH, but a __ negative feedback effect on LH
small, large
why is the testosterone effect on FSH so small?
because inhibin is the necessary feedback agent
it is the ___ form of testosterone that can interact with target cells
unbound/free
what tissues would have testosterone acting directly as testosterone?
penile tissues
what tissues convert testosterone to DHT?
hair follicles and prostate, 5-α-reductase
what tissues aromatize testosterone into estrogen?
certain neurons in the brain
what is the primary version of inhibin produced by the sertoli cells in response to FSH?
Inhibin B
when inhibin Beta units recombine, they produce ___ which ____ FSH secretion
activin, stimulates
activin resides in the ___, where it has a ____ role to ___
FSH producing cells of the pituitary gland, paracrine, enhance the production of FSH
in the fetus, testosterone is responsible for the development of:
epididymis
vas deferens
seminal vesicles
in the fetus, DHT is responsible for the development of:
penis, penile urethra, scrotum, prostate
in puberty, testosterone is responsible for the development of:
penis seminal vesicles musculature skeleton larynx
in puberty, DHT is responsible for the development of:
scrotum
prostate
sexual hair
sebaceous glands
around the ___ month of fetal life, there is a temporary activation of the HPG axis and an increase in ___ secretion. Together, these increase ___ levels
third, hCG, testosterone
what does fetal testosterone do?
- acts on the fetal hypothalamus to ensure that the system is only based on negative feedback
- plays a role in the gender preference and identification of the individual
what explains the activation of the HPG axis at birth?
elevations of excitatory neuronal inputs through glutamate neurons
what is the purpose of the rise in testosterone at birth?
descent of the testes
Kallman’s syndrome
due to a failure of GnRH neurons to migrate to the hypothalamus in fetal development, wind up with hypogonadotropic hypogonadism
how do you treat Kallman’s syndrome?
give the patient testosterone
precocious puberty
excess GnRH comes out of the hypothalamus prematurely
how is precocious puberty treated?
give a GnRH superagonist analog to desensitize the pituitary
androgen insensitivity syndrome
XY genotype, female appearance, undescended testes have to be removed, no female reproductive structures
why do people with androgen insensitivity syndrome not have female reproductive structures?
Y chromosome has SRY gene, manufactures Mullerian inhibitory hormone
how is estrogen made in someone with androgen insensitivity syndrome?
testosterone is still produced by the testes, the testosterone is converted to estrogen by the fat tissue
