Abstract
Abstract
The relationship between the reproductive system and calcitonin secretion was investigated in the rat. Plasma levels of calcitonin were measured in normal and ovariec-tomized rats at basal levels and during calcium challenge. Sensitivity of the normal and operated animals to exogenous calcitonin administration was also studied. Ovariectomy leads to a transient fall in both CT levels and in the secretion of the hormone in response to a calcium challenge. However, a greater sensitivity of ovariectomized animals to salmon calcitonin is maintained after the return to normal of both the basal level of the hormone and of its secretion in response to a calcium challenge. Estrogen substitutive therapy does not restore CT levels and antagonizes the action of exogenously administered CT in ovariectomized rats. These results suggest the existence of a direct or indirect effect of ovarian factors, other than estrogens, on CT secretion.
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