Effects of Thyroid Hormone and Phosphorus Loading on Renal Calcification and Mineral Metabolism of the Rat

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Abstract
Seventy-two young male albino rats were used in 2 experiments designed to study effects of chemical blockage of thyroid secretion and of supplemental thyroxine administration on renal calcification and other criteria of mineral metabolism as influenced by high phosphate intake. Calcium content of kidney mitochondria and whole kidney tissue was increased by high phosphate diets and was inversely affected by level of thyroid activity; phosphorus content of whole kidney tissue, but not of mitochondria, was similarly affected. Histological and chemical studies of kidneys revealed a parallelism between calcification and PAS-stainable material. Percentage retention of dietary calcium and magnesium was markedly depressed in both hypoand hyperthyroid animals. High phosphorus diets decreased the percentage of calcium and magnesium absorption and their excretion in the urine, and hence had little effect on balance. The effects of high phosphate diets on kidney calcification and urinary mineral excretion resemble those of parathyroid hormone and may be a result of induced parathyroid activity. The effect of thyroid hormone on reducing kidney calcification may be related to its effect on mucopolysaccharide metabolism.