THE BIOPHYSIOLOGICAL EFFECTS OF SEX STEROIDS ON BONE AND CYTOKINE NETWORKS IN POSTMENOPAUSAL WOMEN

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The urinary excretion of hydroxy pyridinolin (HP) and lysylpyridinoline (LP) , which are intermolucular crosslinking collagen fibers, were measured and their chronological changes were evaluated following oophorectomy. There was a singnificant increase in HP and LP of the postmenopausal women (p<0.001) . Both HP AND LP of postmenopausal women were three times higher than those of prmenopusal women, and decreased to the same level of premenopausal women between 2 and 3 years after surgery.The changes of vertebral bone mineral density (BMD ; g/cm^2) following oophorectomy were studied using dual energy X-ray absorptiometry (DEXA) , and two biological indices of bone remodeling, urinary deoxypyridinoline (DPyr) for bone resorption and serum intact osteocalcin (hOC) for bone formation were measured at the same time. The rate of bone loss was rapidly between the first and the second year, followed by a slow phase. The bone mass finally reached an osteoporotic level (BMD<0.767g/cm^2) at 12 years after oophorectomy. The DPyr increased to reach a Peak level in the first year, whereas the hOC increased and reached its peak level in the second year after surgery. The maximal bone loss in the first year is considered to be caused by the remarkable increase of bone resorption and the biological delay of the maximal increase in bone formation.