—In response to the letter by Drs Hanson and Melzer, clinical trials are designed and performed with Food and Drug Administration (FDA) guidance and according to FDA requirements. To document the protective effect of an estrogen-progesting combination against endometrial hyperplasia, the FDA has required both a placebo group and an unopposed estrogen group in clinical trials such as ours and others (eg, the 3-year National Institutes of Health [NIH]-supported PEPI trial1).The statement in the introduction of our article regarding withdrawal bleeding referred to results from our pilot study that did include a cyclical CEE-MPA group. In the "Comment" section, we clearly state that a comparative study with continuous NA-EE2 and CEE-MPA has not been done and would be helpful to define differences.
Speroff L. Estrogen Replacement Therapy: New Options, Continuing Concerns-Reply. JAMA. 1997;277(19):1515-1516. doi:10.1001/jama.1997.03540430027017