Postmenopausal osteoporosis: the effect of parathormone and large dose vitamin D3 on the serum calcium level in sex hormone deficient rats.

Rats deprived of adrenal and gonadel sex hormones are more sensitive than normal rats to the hypercalcaemic (osteolytic) effect of parathormone and toxic doses of vitamin D3. It is suggested that sex hormone deficiency and the consecutive decrease of calcitonin sensitivity in postmenopausal osteoporosis makes the patients unprotected against factors inducing increased bone resorption, and this leads over the years of osteoporosis.