CALCITONIN MAY MODULATE PLACENTAL-TRANSFER OF CALCIUM IN EWES

In pregnant ewes bearing twin fetuses and fed an adequate Ca diet, the consequences of calcitonin (CT) deficiency (induced by thyroidectomy performed on day 30 of gestation, associated with daily thyroxine supplementation) differed according to the time of pregnancy. Such a deficiency had no significant effect either on fetal total body Ca content or on placental transfer of Ca in 77 day old fetuses. CT deficiency for 110 days (on day 140 of pregnancy) was associated with an increased Ca concentration in fetal total body and increased placental transfer of Ca from the dam to its fetus, which did not occur in 5 thyroidectomized ewes supplemented with thyroxine and CT. Apparently CT might protect the skeleton of the pregnant female against excessive demineralization by modulating placental transfer of Ca, when such a transfer becomes important, during periods of intense mineralization of the fetal skeleton.