Comparison of progesterone and glucocorticoid receptor binding and stimulation of gene expression by progesterone, 17-alpha hydroxyprogesterone caproate, and related progestins

Binding to progesterone receptors, glucocorticoid receptors, or expression of progesterone-responsive genes is no greater with 17-alpha hydroxyprogesterone caproate than with progesterone. Other mechanisms must account for the beneficial effect of 17-alpha hydroxyprogesterone caproate on preterm birth rates.