[Substitutive hormone therapy in postmenopausal osteoporosis. Are there any contraindications?]

Estrogen deficiency is the main cause of postmenopausal osteoporosis. Replacement estrogen therapy protects the bone by reducing bone resorption and activating osteoblasts, as well as by promoting absorption of calcium and production of calcitonin. These preventive effects are especially marked in cancellous bone, provided estrogen therapy is initiated as soon as menstruation stops. Effects are dose-dependent and efficacy of the treatment is noticeable mainly during the period of administration. The rare contra-indications to estrogen therapy include hormone-dependent cancers, cholestatic jaundice, and large uterine myomas (for which surgical treatment is recommended). Metabolic disorders, arterial hypertension, and thyroid function disorders are less common with the new natural estrogens (estradiol) given orally or percutaneously to avoid hepatic passage of the drug. As for treatment induced cancers, sequential administration of a progestagen protects the endometrium and the relative risk seems negligible for breast cancer. Although concomitant use of a progestagen is mandatory, either natural progesterone or norpregnanes should be given to avoid adverse metabolic effects. Emphasis has recently been put on the role of concomitant progestagen therapy which may promote the formation of bone, probably by competing for glucocorticoid receptors in bone. There is still a need for prospective epidemiological studies, although evaluation methods and the long follow-ups needed raise significant problems.