Daily Variation in Concentration of Plasma Corticosteroid in Hypophysectomized Rats

Abstract

A daily variation in the concentration of plasma corticosteroid hormone is present in hypophysectomized rats implanted with pellets of ACTH and thyroxine. Although ACTH is necessary to maintain a functional adrenal, and thyroxine is required to permit the expression of the plasma corticosteroid rhythm, a normal daily variation in plasma corticosteroid concentration does not appear to depend on the periodic release of pituitary hormones.