Progestogen therapies: differences in clinical effects?

A large number of estrogen/progestogen preparations are available for the treatment of estrogen-deficiency symptoms. These preparations differ in the route of administration, the type and dose of both the estrogen and progestogen. The only indication for the addition of a progestogen is endometrial protection, but, depending on its chemical structure, a progestogen can either enhance (e.g. hot flushes, gonadotropin release, breast-epithelial proliferation and bone mineral density) or antagonize (e.g. endometrium, arterial wall, lipid metabolism, hepatic protein synthesis and mood) the effects of the estrogen component. Available progestogens differ largely in their hormonal pattern and, in addition to their progestogenic and antiestrogenic action on the endometrium they can exert androgenic, antiandrogenic, glucocorticoid and/or antimineralocorticoid effects. There are no comprehensive trials comparing directly the modulating effects of the various progestogens, and clinical and epidemiological data do not allow a definite conclusion on the clinical relevance of differences between progestogens.