Testosterone and the heart
Forget clothes. In a very real sense, testosterone makes the man.
It is responsible for the deep voice, increased muscle mass, and strong bones that characterize the gender. It stimulates the production of red blood cells by the bone marrow. The hormone also has crucial, if incompletely understood, effects on male behavior: it contributes to aggressiveness, and it is essential for the libido, or sex drive, as well as for normal erections and sexual performance. Testosterone stimulates the growth of the genitals at puberty and is responsible for sperm production throughout adult life.
Although testosterone acts directly on many tissues, some of its least desirable effects don't occur until it is converted into another male hormone, dihydrotestosterone (DHT). DHT acts on the skin, sometimes producing acne, and on the hair follicles, putting hair on the chest but often taking it off the scalp. Male-pattern baldness is one thing, but prostate disease quite another: DHT also stimulates the growth of prostate cells, producing normal growth in adolescence but contributing to benign prostatic hyperplasia (BPH) and possibly even prostate cancer in many older men.