Bio-identical steroid hormone replacement: selected observations from 23 years of clinical and laboratory practice.

To maximize the safety and efficacy of human hormone replacement therapy, it is suggested that exact molecular copies of human hormones ("bio-identical" hormones) be administered in physiologic quantities and proportions, following physiologic timing and routes of administration. It is also suggested that physicians return to the practice of monitoring hormone therapy by precise laboratory measurement levels of the hormones administered. This paper also presents clinical and laboratory data concerning appropriate proportions of bio-identical estrogens, the physiologic and supraphysiologic nature of commonly employed doses, estrogen levels achieved by varying routes of administration, and the significant effects of iodine on estrogen metabolism and cobalt on estrogen excretion.