Week 8 - Reproductive Hormones Flashcards
What is the rate limiting step of steroid hormone synthesis?
moving pregnenolone into the endoplasmic reticulum
What are the three layers of the adrenal cortex from superficial to deep?
zona glomerulosa
zona fasiculata
zona reticularis
What is produced in the zona glomerulosa?
aldosterone (mineralocorticoid)
outermost layer of the adrenal cortex
What is the role of aldosterone in the body?
long term regulation of blood pressure
acts on distal convoluted tubule and collecting ducts of kidney where is causes increased reabsorption of sodium
What is produced by the zona fasiculata?
cortisol (glucocorticoid)
middle layer of the adrenal cortex
What is produced by the zona reticularis?
androgens
innermost layer of adrenal cortex
What is the role of dihydrotestosterone (DHT) in embryonic development?
causes differentiation of the penis, scrotum and prostate
type of androgen
What is the role of DHT in later life?
contributes to male balding, prostate growth and sebaceous gland activity
What is the role of androstenedione and dehydroepiandrosterone (DHEA)?
testosterone precursors
adrenal glands produce these molecules which are converted to testosterone in the peripheral tissues
What is Addison’s disease?
deficiency in adrenal gland production of cortisol
leads to loss of body hair and libido
muscle wasting and thin limbs
What is Cushing’s disease?
elevated levels of ACTH (adrenocorticotropic hormone) due to a pituitary adenoma
How does cortisol exert it’s actions?
binds an internal receptor for transcription effects
What is the site of sperm formation?
seminiferous tubules
Which cells are responsible for secreting testosterone?
leydig cells
What hormone stimulates the leydig cells to produce testosterone?
LH
increases conversion of cholesterol to pregnenolone
What hormone acts on Sertoli cells to stimulate spermatozoa development?
FSH
also produces inhiin for negative feedback on FSH
In men, where is most dihydroxytestosterone (DHT) produced?
Sertoli cells
sertoli cells convert testosterone to DHT or oestradiol
DHT is produced by the action of 5-alpha-reductase on testosterone
FSH increases activity of this enzyme
What hormone negatively feeds back to the hypothalamus, inhibiting further release of GnRH, LH and FSH?
testosterone
inhibin negatively feedsback to the anterior pituitary NOT hypothalamus directly
in women, oestradiol controls GnRH release
What is the genital phenotype of male patients who cannot produce any DHT?
male internal, ambiguous external
DHT is needed for development of external genitalia only
What happens to the genitalia of a baby in the absence of DHT?
female external genitalia will form regardless of other factors
What is androgen sensitivity syndrome (AIS)?
mutation in the gene AR which normally makes an androgen receptor
body does not respond to androgens so the external genitalia of the child appear female even though they are genetically male
What is the action of testosterone and DHT on secondary sexual characteristics?
promotes muscle growth
induces male hair growth pattern
causes the voice to deepen (vocal chord thickening)
What is the mechanism of action of the enzyme aromatase?
aromatisation of androgens to estrogens
In men, where is most DHT produced?
Sertoli cells by the action of 5-alpha reductase on testosterone
