Effect of Androstenedione Ingestion on Plasma Testosterone in Young Women; a Dietary Supplement with Potential Health Risks

Androstenedione is readily available as a “dietary supplement” and can be sold without restriction in most countries, including the US and UK. Manufacturers market androstenedione as a “prohormone” that can increase blood testosterone concentration, thereby increasing lean body mass and strength. It is available in capsules purported to contain 50, 100, or 300 mg of the steroid, and the manufacturers suggest that the “desired” effects can be gained by taking 100–300 mg/day orally. However, a single dose of 100 mg/day is insufficient to increase serum testosterone concentrations in men (1)(2)(3)(4). Even with higher “recommended” doses of either 200 or 300 mg/day (given as either single or multiple administrations), no significant increase has been observed in most studies (1)(3)(5), albeit in one investigation, 4 of 14 men had testosterone concentrations that exceeded the reference interval (2). The contribution of these administered amounts of androstenedione to the plasma testosterone concentration appears to be relatively small compared with the large amount of testosterone secreted by the testes.No comprehensive study has been reported regarding the effect of oral androstenedione administration on plasma testosterone in women. However, there is an indication that it can be increased considerably, based on limited data from two women, obtained by a methodology based on paper chromatography and conversion of androgens to estrogens for fluorometric analysis (6). The plasma concentration of testosterone in women of a reproductive age is ∼1/10th that found in men, and the proportion arising from peripheral conversion is much greater (7). Although ∼14% of androstenedione in blood is converted peripherally to testosterone in both men and women, the amount converted accounts for approximately one-half the circulating testosterone in the female (7)(8). Hence, ingestion of even a single 100 mg capsule of androstenedione is …