Influence of Thyroid Function on the Metabolism of the Anterior Pituitary Gland

The weight and rate of oxygen consumption of the anterior pituitary gland of the male Sprague-Dawley rat were observed to decline with age. Thyroidectomy, administration of thiouracil or propylthiouracil, and castration significantly elevated pituitary weight, while all but the latter procedure resulted in increased oxygen consumption of this gland. Adrenalectomy was without effect in these respects. Pituitary hypertrophy after thyroidectomy was associated with hyperemia and increased water and protein content. No changes were observed in glucose utilization, lactate production, and levels of succinic dehydrogenase and cytochrome oxidase in the pituitary gland following thyroidectomy. Administration of thyroxine to thyroidectomized rats restored normal pituitary weight and respiratory activity. Diiodothyronine and triiodothyronine were somewhat less effective than thyroxine. Diiodotyrosine and potassium iodide were ineffective. The relationship of pituitary metabolism to protein hormone synthesis in this gland is discussed.