[Ultrastructural changes in the thyro- and somatotropes of hypothyroid rats as affected by exogenous somatotropin].

The state of somatotropic and thyrotropic adenohypophyseal functions of thyroidectomized rats after chronic injections of bovine somatotropin was studied. The adenohypophyseal somatotropin content increased by 22% per gland. The blood serum immunoreactive thyrotropin concentration was 0.925 +/- 0.063 microgram/ml in intact animals, 3.99 +/- 0.74 microgram/ml in thyroidectomized- and 1.27 +/- 0.19 microgram/ml in thyroidectomized rats, given somatotropin. According to electronic microscopy, hypothyrosis is characterized by an elevated functional somato- and thyrotrop activity, markedly decreased after somatotropin injection.