DOES ESTROGEN REPLACEMENT THERAPY INFLUENCE PARATHYROID-HORMONE RESPONSIVENESS TO EXOGENOUS HYPERCALCEMIA IN POSTMENOPAUSAL WOMEN

In postmenopausal women PTH suppression by exogenous calcium is reduce d. To test whether this finding might be caused by estrogen deficiency 9 postmenopausal women were given transdermal estradiol (E2) treatmen t for 3 months at a dose of 100 mug/day. PTH reactivity to iv administ ration of CaCl2 was determined before and at the end of the E2-treatme nt period. Compliance to treatment was checked by determination of ser um levels of E2 and FSH. The E2 level rose from 0.1+/-0.02 (mean+/-SE) to 0.46+/-0.10 mmol/l p<0.01), whereas the corresponding FSH level de clined from 77.5+/-7.4 to 33.9+/-5.7 U/l p<0.01). This suggests good c ompliance. At the end of E2-treatment period calcium administration in duced a higher PTH suppression as compared with control value (the PTH decremental area 2123+/-270 vs 1253+/-253 ng/l x min, p<0.05), althou gh a lower calcemic response was attained (the Ca incremental area 32. 6+/-6.1 vs 47.4+/-4.5 mmol/l x min, p<0.05). These results imply that parathyroid glands are dependent on an adequate estrogen provision to respond normally to serum calcium changes.