Progestational potency of oral contraceptives: a polemic.

Dickey and Stone have attempted an evaluation of progestational potencies of oral contraceptives based upon such uterine criteria as subnuclear vacuolization and delay of menses. Their review, unfortunately, is marred by numerous errors which vitiate the potency estimates. The actions of progestagens in target organs depend upon the specific binding of the compounds to a protein receptor that is produced by estrogen treatment. Potency of hormones depends ultimately upon this binding. Since it seems unlikely that specific binding occurs in such nontarget sites as the blood vessels, direct potency relationships are highly improbable between diverse phenomena. Possible relationships between oral contraceptives and specific side effects must be studied in relationship to individual side effects and particular contraceptive products. Possible coincidental activities, no matter how analyzed, are unlikely to contribute meaningfully to our understanding of these drugs.