Methyltestosterone (MT) is the 17-methyl-substituted synthetic derivative of testosterone, which as an androgen has primary therapeutic value in males, treating hypogonadism, delayed puberty, and impotence. Secondarily, it has had palliative value in treating metastatic breast cancer in females. The drug stimulates receptors in organs and tissues to promote growth and development of male sex organs and maintains secondary sex characteristics in androgen-deficient males. It is available by prescription under various trade names, including Android®, Oreton Methyl®, Testred®, and Virilon®, among other names. In laboratory animal studies, MT elicits masculinization of female fetuses following prenatal administration in rats and rabbits of 10 µg/day by the subcutaneous route, and intersex puppies upon dietary administration of up to 150 µg/kg/day to bitches over several months. MT is a large hydrophobic molecule. It is of low polarity in comparison to the other human developmental toxicants. MT can participate in donor/acceptor hydrogen bonding.