effect). Androgens also control metabolic effects during growth in adolescence and
stimulate protein synthesis (causing “nitrogen retention”) (their anabolic effect).
Testosterone (5.45) is the prototypic androgen sex hormone. Testosterone is synthe-
sized by the testes, and must be reduced to dihydrotestosterone (5.46, DHT) before it
will bind to the receptor. Among highly active synthetic testosterone analogs, 7α-
methyl-19-nortestosterone (5.47) and oxandrolone (5.48) have about 100 times greater
activity than testosterone as androgens. 17α-Methyltestosterone (5.49) is orally active.
The distinction of anabolic from androgenic action is important in the anabolic
therapy of such wasting conditions as cancer, trauma, osteoporosis, and the effects of
immobilization. These conditions necessitate nitrogen and mineral retention; however,
the masculinizing effects of androgenic agents would be undesirable in female patients.
Fluoxymesterone (5.50), the 9α-fluoro-11-hydroxy-17α-methyl derivative of methyl-
testosterone, has 10 times the androgenic and 20 times the anabolic activity of the
parent compound, but is used mainly as an androgen in hormone-replacement therapy,
hypogonadism, and some forms of breast cancer. Some other anabolic agents are
methandrostenolone (5.51), and stanozolol (5.52), clostebol, and nandrolone. Use of
anabolic steroids by athletes is a widespread but dangerous and banned misuse of these
drugs. Nevertheless, their use does elicit protein anabolic effects and is thus associated
with enhanced muscle bulk and more rapid recovery after injury. A nonvirilizing
HORMONES AND THEIR RECEPTORS 329