Ovarian steroids modulate the action of calcitonin in women.

Slow i.v. infusion of salmon calcitonin into normal women led to a transient increase in plasma concentrations of cyclic AMP and to a decrease in plasma calcium, which was maintained for at least 2 h. These responses were significantly reduced in the same patients after hysterectomy and ovariectomy. In contrast, maintenance of the ovaries at the time of surgery, or substitutive hormonal therapy, seemed to restore the sensitivity to exogenous calcitonin, suggesting a permissive role of ovarian steroids in the effect of calcitonin. The most likely explanation for this phenomenon is that these hormones influence either the number of calcitonin receptors or the coupling of the receptors to the functional unit of bone adenylate cyclase.