Excessive vitamin D content of a standard iron-deficient diet for rats

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Abstract
1. The observation that thyroid C cell hyperplasia occurred in rats given the iron-deficient diet described by McCall, Newman, O'Brien, Valberg & Witts (1962) prompted a closer study of the preparation and constituents of this diet..2. It became apparent that there was a discrepancy between the amounts of fat-soluble vitamins in the dietary formulation reported and the supposed final content of the diet. A diet prepared as described by McCallet al.(1962) contains 1000 μg (40000 i.u.) ergocalciferol and 10 μg (14 500 i.u.) retinyl palmitate/kg..3. An experiment was designed to study the effect of Fe-deficient and Fe-supplemented, high-vitamin-D diets, and an Fe-supplemented, normal-vitamin-D diet, on thyroid C cell volume and serum calcium concentration..4. Thyroid C cell volumes and serum Ca concentrations were significantly higher in both groups given excess vitamin D than in the group given the Fe-supplemented, normal-vitamin-D diet. It is evident therefore, that hypervitaminosis D was the cause of the morphological and biochemical changes found in rats given the McCallet al.(1962) diet.