Endocrine Unit

Bone status in the oophorectomized rat

H A Morris, T C Durbridge, A G Need, R J Moore, P D O'Loughlin, P Baldock, R A Mason, S Schulz, P H Anderson, D Horton

The award of a three-year project grant to study the interaction between oestrogens and androgens and bone metabolism has allowed the study of the molecular basis of bone cell responses to the steroid hormones which play a fundamental role in maintaining skeletal strength. Administration of oestrogen from subphysiological to supraphysiological doses has been found to be associated with increasing mineral deposition with increased trabecular thickness. It is likely that this effect is responsible for the significant reduction in fractures following oestrogen therapy in postmenopausal women. Androgens have been found to stimulate the bone forming cells to synthesize bone proteins as well as enzymes necessary for the deposition of mineral and this action is further stimulated by the addition of oestrogen. Oestrigen deficiency causes a reduction in intestinal calcium absorption and preliminary studies suggest this is a result of interference with the action of vitamin D. As well, androgen deficiency in female rats was found to increase the loss of calcium in the urine, an effect which was augmented by combined oestrogen deficiency.