1. A group of women who had undergone hysterectomy and bilateral salpingooophorectomy were studied and subsequently given either 20–40 μg of mestranol per day or a placebo for 1 year.
2. The administration of mestranol to these oophorectomized women for 1 year was associated with significant falls in serum calcium and phosphorus concentrations, a fall in urinary calcium excretion and a rise in relative urinary phosphorus excretion.
3. It is suggested that these results are consistent with an increase in sensitivity to calcitonin and that the relative hyperphosphaturia reflects a compensatory rise in parathyroid hormone activity.