Thyroid function and plasma phosphate level in rat.

Abstract

The ability of thyroxine, or triiodothyronine, to produce an increase in the plasma phosphate level of normal or thyroparathyroidectomized rats is known. In the present paper, the effect of thyroidectomy or antithyroid drug treatment was studied. Both procedures caused a fall in plasma phosphate whether parathyroid glands were present or not. Removal of the pituitary gland did not alter the hyperphosphatemic activity of thyroxine. This result is consistent with the conclusion that growth hormone is not involved in this particular thyroxine action. A progressive rise in plasma phosphate level was observed during the re-establishment of thyroid function in the hypophysectomized rat by thyroid-stimulating hormone replacement therapy. Our experimental conditions failed to reveal any change in plasma calcium or phosphate level due to the removal of thyrocalcitonin. It is suggested that thyroid function through its iodinated hormones contributes to the determination of the physiological plasma phosphate level i...