Acidophil Regranulation and Increased Growth Hormone Concentration in the Pituitary of Thyroidectomized Rats After Cortisol Administration

Abstract

Female rats of the Long-Evans strain were thyroidectomized at 28 days of age by a combination of surgery and 131I. Fortynine days later, when growth stasis was complete, they were injected with 1 mg of cortisol acetate daily for 14 days. The rats were then killed for evidence of acidophil regranulation and the presence of growth hormone, as determined by the tibia test, in their anterior pituitaries. The acidophils increased from 0 to 60% of normal after cortisol administration. Although appearing cytologically active, they did not contain the normal content of specific granules. The growth hormone concentration in these pituitaries was estimated to be more than 8 times that in the thyroidectomized controls but 8 times less than in the normal. It was concluded that the presence of acidophil granulation is still a reliable sign for growth hormone in the pituitary and not necessarily dependent on the presence of thyroxine or related compounds. (Endocrinology74: 784, 1964)