Prolonged effect of estradiol on calcitonin secretion.

Incubation of thyroparathyroid gland from 8-day-old rats with estradiol (10(-7) and 10(-9) M) and progesterone (10(-9) and 3 X 10(-10) M) resulted in stimulation of CT secretion. The effect of the gonadal steroids on CT secretion occurred at near physiological concentrations and persisted for at least 73 h. The studies demonstrate that exposure to gonadal steroids results in direct and prolonged stimulation of CT secretion. Therefore the decrease in bone resorption observed after the administration of gonadal steroids in vivo may at least in part be mediated via stimulation of CT secretion.