[Prevention of postmenopausal bone loss with estrogens. Which molecule, which scheme, which dose?]

Estrogen therapy prevents post-menopausal bone loss. Minimal effective dosage, or best, estradiol circulating blood level threshold, is difficult to assess but necessary for broadly used drugs. Concerning oral estrogens, only one minimal dose, statistically efficient for a large group of subjects can be determined. Because of individual metabolic variability, this dose is high and non-adjustable. Cutaneous estrogens administration can theoretically overcome this inconvenience and allow a precise adjustment of circulating blood level. However, if a drug will develop bioavailability changes or poor compliance, it will be necessary to increase daily dosage in order to abolish these variations. This will result in an overestimate of the minimal estradiol circulating blood level threshold. This overestimate is directly dependent on the galenic properties of the substance used and the compliance which will result from its use. Lastly, the more individual results will show dispersal, the more the patient will need blood level controls.