Androgens

ANDROGENS

(Male Sex Hormones)

These are substances which cause development of secondary sex characters in the castrated male. That testes are responsible for the male characters is known since prehistoric times. Its endocrine function was established by Berthold in 1849. Testosterone was isolated, its structure worked out and synthesized by the year 1935.

Natural Androgens 

Testes of adult male produce 5–12 mg of testosterone daily, a part of which is converted in extraglandular tissues to the more active dihydrotestosterone; by the enzyme steroid 5 αreductase; cholesterol is the starting material and the same pathway depicted in Fig. 20.1 is utilized. Adrenal cortex produces small quantities of dehydroepiandrosterone and androstenedione which are called ‘weak androgens’ (potency 1/20 to 1/30), but are infact inactive as such and derive their weak activity from partial conversion to testosterone by peripheral tissues. Adrenals themselves do not produce significant quantity of testosterone. In women ovary produces small quantity of testosterone; this together with that derived indirectly from adrenals amounts to 0.25–0.5 mg/day.

Androsterone It is a metabolite of testosterone which is excreted in urine. It has 1/10 the activity of testosterone.

Synthetic Androgens 

Methyltestosterone and fluoxymesterone are 17alkyl substituted derivatives of testosterone which are orally active because of resistance to first pass metabolism, but have submaximal androgenic efficacy and potential to cause cholestatic jaundice. Other orally active compounds are testosterone undecanoate which administered as oily solution is absorbed through lymphatics bypassing the liver, and mesterolone. A number of lipidsoluble esters of testosterone have been produced, suitable for injection in oily vehicle, from which they are absorbed slowly and exert prolonged action after deesterification in the body.