Estrogens and progestogens conserve bone in rats deficient in calcitonin and parathyroid hormone.

To examine the abilities of estrogens and progestogens to slow bone resorption and conserve bone in ovariectomized rats deficient in calcitonin (CT) or parathyroid hormone (PTH), nine groups of animals with 45Ca-labeled bones were studied for 12 wk. Rats were thyroidectomized (TX), parathyroidectomized (PTX), or given sham neck operations (Sham) and treated orally with either estrogen, 300 micrograms 17 beta-estradiol.kg body wt-1.wk-1; progestogen, 500 micrograms norethisterone acetate.kg body wt-1.wk-1; or placebo (Plac). The TX rats had parathyroid autografts and thyroxine replacement. In all surgical groups, estradiol (E2) and norethindrone (Nor) slowed urinary 45Ca excretion and conserved bone (P less than 0.001). However E2 lowered urinary hydroxyproline more than Nor. Total body Ca values (mg +/- SD) were Sham + Plac, 3,079 +/- 201; Sham + E2, 3,886 +/- 335; Sham + Nor, 3,567 +/- 459; TX + Plac, 3,123 +/- 159; TX + E2, 3,869 +/- 235; TX + Nor, 3,540 +/- 422; PTX + Sham, 3,067 +/- 249; PTX + E2, 3,775 +/- 414; PTX + Nor, 3,635 +/- 467. Importantly, E2 and Nor conserved bone as effectively in TX and PTX groups as in Sham rats, although the PTX rats had slower bone resorption and lower plasma 1,25-dihydroxyvitamin D values (P less than 0.001) than groups with intact parathyroids. We conclude that the effects of estrogens and progestogens to slow bone resorption and conserve bone are independent of CT and PTH. These findings appear relevant to the pathogenesis and treatment of postmenopausal osteoporosis.

[1]  J. Feyen,et al.  Prostaglandin production by calvariae from sham operated and oophorectomized rats: effect of 17 beta-estradiol in vivo. , 1987, Endocrinology.

[2]  S. Epstein,et al.  Serum Bone Gla Protein and the Vitamin D Endocrine System in the Oophorectomized Rat , 1988 .

[3]  J. Wishart,et al.  Treatment of postmenopausal hyperparathyroidism with norethindrone. Effects on biochemistry and forearm mineral density. , 1987, Archives of internal medicine.

[4]  D. Fraser,et al.  A new mechanism for induced vitamin D deficiency in calcium deprivation , 1987, Nature.

[5]  D. Kalu,et al.  Evaluation of the role of calcitonin deficiency in ovariectomy-induced osteopenia. , 1984, Life sciences.

[6]  S. Kukreja,et al.  Effects of estradiol and progesterone on calcitonin secretion. , 1986, Endocrinology.

[7]  D. Feldman,et al.  Glucocorticoid receptors and inhibition of bone cell growth in primary culture. , 1977, Endocrinology.

[8]  Kenneth G. Mann,et al.  Evidence of estrogen receptors in normal human osteoblast-like cells , 1988 .

[9]  A. Goulding,et al.  Effects of Chronic Prednisolone Treatment on Bone Resorption and Bone Composition in Intact and Ovariectomized Rats and in Ovariectomized Rats Receiving β-Estradiol , 1988 .

[10]  C. Christiansen,et al.  UNCOUPLING OF BONE FORMATION AND RESORPTION BY COMBINED OESTROGEN AND PROGESTAGEN THERAPY IN POSTMENOPAUSAL OSTEOPOROSIS , 1985, The Lancet.

[11]  J. Anderson,et al.  Osteoporosis after oophorectomy in the mature female rat and the effect of oestrogen and-or progestogen replacement therapy in its prevention. , 1972, The Journal of endocrinology.

[12]  H. DeLuca,et al.  Effect of estrogen on calcium absorption and serum vitamin D metabolites in postmenopausal osteoporosis. , 1980, The Journal of clinical endocrinology and metabolism.

[13]  R. Lindsay,et al.  Prevention of Bone Mineral Loss on Postmenopausal Women by Norethisterone , 1985, Obstetrics and gynecology.