A steroid hormone precursor once sold as a dietary supplement promising increased testosterone, energy, strength, and muscle growth. Marketed aggressively to athletes and bodybuilders in the 1990s, it converts in the body to testosterone and estrogen through pathways that proved unpredictable: rather than reliably boosting testosterone, it often raised estrogen, while side effects included hormonal disruption, aggressive behavior, mood swings, hair loss, acne, and cardiovascular risks. Sports authorities banned it, and regulators in the United States reclassified it as a controlled anabolic steroid, removing it from the supplement market. Its story is a landmark in supplement regulation, demonstrating how a product sold as a natural performance aid functioned pharmacologically as a steroid with all the attendant dangers.