Effect of a calcium-deficient diet and vitamin d on thyrocalcitonin in cows

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The plasma thyrocalcitonin (TCT)- like activity, determined by biologic assay after oxycellulose extraction, in nonpregnant-nonlactating cows was 87 ± 21 MRC mU/1 and the gland content of TCT was 624 ± 64 MRC mU/g. The administration of a calcium-deficient diet to adult cows for 30 days resulted in a significant decrease in serum concentration of calcium and a reduction in the thyroid content of TCT to 55% of controls. Plasma TCT-like activity was not altered significantly despite a lowering of the serum calcium. Cows receiving the calcium-deficient diet with the addition of vitamin D (30 million units daily) from the 20th to the 30th day had a reduction of TCT in the thyroid to 32% of controls. The administration of vitamin D to cows receiving the calcium-deficient diet did not result in a significant increase in the serum concentration of calcium. Plasma TCT-like activity was not changed from that of control cows. The reduction in thyroid stores of TCT in both groups of experimental cows occurred in the absence of a significant hypercalcemic stimulus. © 1972 by The Endocrine Society.

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