In October 1996, a new category of sports supplements emerged. The supplement that started this trend was introduced to the bodybuilding market by the Osmo company and was called androstenedione or simply "andro." Although andro was new to the bodybuilding and sports supplement market, it was not a newly discovered substance. Andro had been discovered shortly before testosterone in 1935. German scientists had been searching for a then-unknown male hormone, whose effects were clear in both humans and animals, but no one had yet isolated the active hormonal compound. When andro was found in urine samples, scientists making the discovery erroneously thought that they had reached a eureka moment and had finally isolated the mysterious "male factor," as it was called. But the scientists knew that the as yet unidentified male factor affected the growth of the prostate gland, yet andro didn't seem to affect the gland as expected, leading the researchers to realize that andro was not the primary androgen in men, but rather an intermediary substance produced in the pathway of synthesis for the primary hormone, which turned out to be testosterone. Eventually, they realized that andro was an androgen that was produced in both the testes and the adrenal glands, and was a step along the way to the production of testosterone in the Leydig cells of the testes. Andro also turned out to be an immediate precursor to the production of a weak type of estrogen found predominantly in older women called estrone.
When the scientific world realized that testosterone was the primary androgen in men, andro was relegated to a state of relative obsolescence. It was of interest only to biochemists who studied it as part of the testosterone synthesis pathway. But it was the location of andro in this pathway that led to its resurrection in prominence years after its discovery. This newfound recognition of the properties of andro began with the 1963 publication of a medical journal article in which it was shown that ingestion of andro in women always caused a rapid and significant rise in the women's testosterone levels. This finding didn't exactly set the scientific world on fire, since it was well-known that andro was the final step in the conversion of cholesterol into testosterone. It wasn't a surprise that a substance such as andro would convert rapidly to testosterone in women, who produce about 1/10 as much testosterone as do men. Later research showed that andro was highly significant for women's health since it acted as a precursor not only for testosterone production in women but also estrogen. Indeed, andro is the primary source of 50% of the testosterone production in women, where it's produced in a woman's ovaries and adrenal glands. Some women suffer from a disease called Polycystic Ovarian Syndrome, which is notable for producing higher than normal androgen levels in females . . .