Physiologic Basis of Disorders of Androgen Metabolism

Evidences of virilization have been correlated with the daily production of testosterone and its effective blood level. These depend on the rates of secretion of testosterone, the rate of conversion from other plasma precursors, the amount of testosterone-binding protein present in plasma, and the clearance of testosterone from plasma. These facets of testosterone metabolism can now be quantified. In prepuberal children and normal women about half of the plasma testosterone is secreted, and the rest is produced from other plasma steroids secreted by the adrenal cortex. In men more than 95% of the plasma testosterone is secreted by the Leydig cells. A variety of ovarian and adrenal tumors may secrete testosterone in equal or greater amounts. By contrast, in congenital adrenal hyperplasia, the elevated plasma testosterone level is due to the hypersecretion of androstenedione by the adrenal cortex and its subsequent conversion to testosterone. The methods used in these physiologic studies are applicable to the clinical examination and diagnosis of suspected hypogonadism, virilization, and hirsutism. Illustrative cases are discussed.