Functions of male sex hormones

what is testosterone and how is it formed?

it is a steroid hormone made from cholesterol and androstendione in the leydig cells

how does testosterone bring about DNA changes?

via binding to intracellular androgen receptors to DNA in the nucleus

How is testosterone transported?

• 65% → Sex steroid binding globulin

• 33% → albumin

• 2% → free

How is testosterone regulated?

HPA negative feedback regulation which inhibits GnRH and LH when testosterone is too high

name the 3 masculinising effects of testosterone?

1. primary sex organ → T is released in the 7th week → descends testes

2. secondary sex organ → DHT induces differentiation of external genitalia, spermatogenesis, and fertility

3. secondary sex characteristics → growth of hair, deep voice, acne

cause of baldness?

excess DHT in the scalp

What are the metabolic functions of testosterone?

• protein anabolic effect → increased bone matrix due to calcium retention + 50% increased muscle mass

• high BMR → 5-10%

• more RBCs → due to bone marrow + EPO stimulation they have 700,000 more RBCs/cubic ml

• more fluid retention due to reabsorption of sodium

• Androstenedione improves CNS function (mood, memory, sex drive) as well as immune system stimulation

what are the side effects of anabolic steroids?

• severe acne

• mood changes

• kidney, liver and heart disease

• decreased sperm count

• testicular atrophy and breast development

• suppression of LH secretion → reduction in endogenous androgen

difference between primary and secondary hypogonadism?

primary (total) involves congenital absence of testes and castration whereas secondary involves failure of AP to secrete LH and hypothalamus to secrete GnRH

How does hypergonadism differ in adults vs children?

it is rare and mostly due to a tumour

in adults → increased sexual function

in children → precocious pseudopuberty

what are the characteristics of eunuchism?

• absence of testosterone

• failure of spermatogenesis

• tall with thin bones and weak muscles

• decreased BMR

What is hypothalamic eunuchism associated with?

disturbance of feed centre → adiposogenital syndrome

what are the characteristics of male andropause (post-pubertal hypogonadism)?

• depressed sexual function (sterility)

• poor development of secondary sexual features

• patient is irritable and depressed