Sex Difference in Thyroidal Response to Administration of Progesterone in the Rat

Summary

In intact female rats, thyroidal radioiodine uptake and plasma PB¹³¹I were greater in estrus, intermediate in diestrus and least in continuous diestrus produced by progesterone. Progesterone also depressed thyroidal radioiodine uptake and plasma PB¹³¹I in hypothalamic lesioned female rats, but was without effect in oophorectomized rats. In contrast, progesterone increased thyroidal radioiodine uptake and plasma PB¹³¹I in intact, castrated and hypothalamic lesioned male rats. The increase was roughly proportional to the doses of progesterone administered. It was concluded that there is a sex difference in thyroidal response to progesterone in the rat.