Testosterone is a powerful male sex hormone

Some medical discoveries are over-ballyhooed. Among them is testosterone, now sometimes puffed as a great rejuvenator. Actually there is no such thing as a "rejuvenator."
Testosterone is a powerful male sex hormone which is manufactured by male sex glands, was discovered in The Netherlands in 1935, and made synthetically in Switzerland the same year from the fat of sheep's wool. In the hands of competent doctors, testosterone has definitely helped cases of pathological sex inadequacy, by bringing the patient's sexual functioning up to par. But there is no evidence that it retards the natural sex decline and general debility of old age. Last week the experiments of Dr. V. G. Korenchevsky of Britain's Lister Institute proved that testosterone prolongs potency in neither man nor beast. Dr. Korenchevsky worked with rats—which, for medical research purposes, are almost miniature human beings.
The scientist found that testosterone does increase the size of external sex organs in elderly rats—"but it does not cause any noticeable improvement in their appearance and behavior. As these organs . . . may be well preserved in otherwise senile animals and men, the absence of a rejuvenating effect is not surprising. . . . Without simultaneous improvement of the general condition, this sex stimulation is biologically unnatural and in human patients is medically undesirable."
Moreover, while the external organs of stimulated rats grew larger, the sex glands themselves grew smaller.

Although women undergo a sudden decline in the female sex hormone estrogen during menopause, most men experience a gradual tapering off in testosterone production that begins in their forties and continues at about 1 percent a year. That decline, sometimes referred to as "andropause," is the subject of medical debate, with some researchers saying it is predictable and normal and others saying it is associated with diseases and conditions that can be kept at bay by taking additional testosterone.
The FDA has approved testosterone only for hypogonadism, a steep decline in hormone production triggered by surgery or disease that harms the testes or pituitary gland. But the IOM panel concluded that a significant majority of the more than 1.75 million testosterone prescriptions in 2002 were for men who did not have the condition. Once the FDA has approved a drug for one condition, doctors can legally prescribe it for any medical purpose. Such "off- label" uses are widespread -- and sometimes controversial.
The sharp increase in testosterone use since 1999 coincided with the FDA's approval of new and easier ways to administer the drug. Testosterone used to be given only by monthly injections, but men can now get it as a patch or a gel. Because of the way testosterone acts in the body, it is not given in pill form in the United States.