HRR: male repro I Flashcards
Which gonadotropin predominates in stimulation of Sertoli cells?
FSH
Which gonadotropin predominates in stimulation of Leydig cells?
LH
What are the 3 negative feedback players in male sex hormones in order of strength?
Testosterone, E2 (estradiol), DHT
What does negative feedback to hypothalamic-pituitary-testes axis result in?
Fewer GnRH pulses and pulses of lower amplitude
What is the main player in hypothalamic pituitary testes feedback?
Estradiol
What does inhibin B do?
Inhibit FSH
How are hormones able to cause negative feedback to GnRH?
Through KNDY neurons! These have receptors for the hormones, while GnRH neurons do not
What is GPR54?
Same as Kiss1 receptor; kisspeptin binds here to regulate GnRH secretion
Where does the majority of DHT come from?
Peripheral tissues, NOT testes
What enzyme converts testosterone to estradiol?
Aromatase
When is the concentration of plasma testosterone highest?
Around 6-8 am, but it follows circadian cycle! This means if ‘nighttime’ is our morning, testosterone would be higher at night. Basically, before whenever we wake up.
Someone needs their testosterone checked. When should they come in?
In the morning, when it should be most abundant
What are the mechanisms of biologic action of testosterone?
- Can bind to androgen receptor
- Can be converted to DHT by 5a-reductase
- Can be converted to estradiol by aromatase
What are the types of 5a reductase and where do we find them?
Type 1: liver, non-genital skin
Type 2: androgen target tissues (prostate, epididymis, genital skin, liver)
Is aromatase unidirectional or bidirectional?
Unidirectional
Describe DHT binding a receptor.
It has a much higher affinity than testosterone and has slow dissociation. This is because the receptor essentially folds over DHT.
Which is more potent in the fetus: testosterone or DHT?
DHT! It is needed for development of male external genitalia!
What elements in the male reproductive system is DHT directly responsible for the development of?
Penis, urethra, scrotum, prostate
What hormone is appropriate for growth plate fusion?
Estrogen
What is ABP?
Made in the testes by seminiferous tubules and helps keep testosterone locally, because it’s super important for local functioning.
What are major functions of Sertoli cells?
Maintain seminiferous tubules, provide nutrients and growth to germ cells, release sperm and secrete fluids, and produce hormones like ABP.
What is anti-mullerian hormone?
Hormone made by Sertoli cells that is needed to suppress development of female characteristics in males.
