Testosterone

When the German physiologist Arnold Adolph Berthold castrated roosters in 1849, the results were likely not surprising. He was undoubtedly aware that as early as 2000 BCE male farm animals were castrated to make them more amenable to carrying out their chores. Moreover, Roman emperors who feared assassination, like Constantine in the fourth century, were reported to surround themselves with unaggressive eunuchs.

Berthold, working at the University of Gottingen in Germany, castrated prepubescent male chickens that, upon maturity, failed to exhibit the characteristic physical and behavioral signs associated with roosters. He also castrated adult roosters and observed that they stopped fighting among themselves, had a loss of sex drive, and stopped crowing. Then, after he placed the testicles into a rooster’s body cavity, its normal behavior was restored. With these experiments, Berthold established himself as a pioneer in the discipline of endocrinology, demonstrating the role of the gonads in the development of secondary sex characteristics.

The British artist Francis Smith (1722–1822) painted Kisler Aga, Chief of the Black Eunuchs and First Keeper of the Serraglio between 1763 and 1779. The word eunuch typically refers to a castrated man who accordingly has little testosterone. In ancient times, eunuchism was often practiced to render slaves less aggressive and more servile.

Four decades passed before Charles-Édouard Brown-Séquard picked up the trail where Berthold left off. Brown-Séquard was a highly distinguished Mauritian-born physiologist and neurologist who taught in London, Paris, and Cambridge, MA (Harvard). He had conducted research on the physiology of the spinal cord and postulated that substances secreted into the bloodstream have effects on distant organs. (These hypothetical substances, the hormones, were to be discovered several decades later.) In 1889, Brown-Séquard authored a paper that appeared in Lancet, one of the world’s leading medical journals. In it, he reported that after injecting himself with a liquid extract prepared from the testicles of dogs and guinea pigs, he experienced mental and physical rejuvenation, feeling many years younger than his age of seventy-two. Regrettably, Brown-Séquard had experienced a classic placebo response. Notwithstanding promotional claims to the contrary, carefully controlled studies in recent years have failed to produce any such rejuvenating effects in aging men. Brown-Séquard, Robert Louis Stevenson’s neighbor in London, was said to be the inspiration for Dr. Jekyll and Mr. Hyde.