Androgens Flashcards
Where are androgen produced in men?
Testes (95%) and Adrenal glands (5%)
Where are androgens produced in women?
Ovaries and adrenal glands
List 5 examples of androgens
- Adrostenediol
- Androstenedione
- DHEA
- Testosterone
- Dihydrotestotestosterone (DHT)
What is the composition of testosterone in the blood?
60% bind to Sex-hormone-binding globulin
38% bind to albumin
2% free and active
What does free testosterone do?
Can bind to androgen receptors or be converted into dihydrotestosterone or oestradiol
Why are men more likely to get CDV disease?
Because their higher levels of testosterone increases very low-density and low density lipoprotein but decreases high-density lipoprotein
Describe 6 stages of the hypothalamic-pituitary-testicular axis
- Starts with hypothalamus which produces GnRH in a pulsatile manner and acts on the anterior pituitary
- Causes anterior pituitary to produce FSH
- FSH causes sertoli cells in testis to produce inhibin and causes increase in spermatogenesis
- Negative feedback: as inhibin concentration increases it causes FSH concentration to decrease
- Increase in GnRH also causes anterior pituitary to increase production of LH which acts on the Leydig cells to increase production of testosterone which has two effects. 1. Diffuses into seminiferous tubules for spermatogenesis. 2. Peripheral targets (muscle, liver, fat and skeleton
- Testosterone has negative feedback on anterior pituitary to decrease FSH,
What is the function of aromatase?
Converts androgens to oestrogen
Why can deficiency in aromatase cause osteoporosis?
Because a deficiency causes lower oestrogen levels so taller stature (due to later fusion of epiphyses)
What is the result in overproduction of aromatase?
Increase in oestrogen so increase in adipose tissue and feminine feature
Which enzyme converts testosterone to dihydrotestosterone?
5-alpha-reductase
