Hot flashes and androgens: a biological rationale for clinical practice.

Hot flashes are the most prevalent symptom of menopause. Although the etiology of hot flashes has yet to be determined, it is increasingly apparent that the physiology of the underlying vasomotor instability is multifactorial. Estrogen and androgen receptors are present in the areas of the central nervous system relevant to hot flashes. Androgens are central to the synthesis of estrogen and to the bioavailability of free estrogen in peripheral tissues. In addition, androgens have direct central nervous system effects that modulate other endocrine factors associated with hot flashes. The pharmacodynamic differences of testosterone and methyltestosterone are briefly reviewed in the context of choice for individualized clinical use.