The Interrelationship between Thyroid Activity, Dietary Fat and Lipogenesis

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Abstract
Immature rats receiving a low fat diet and thyroid showed retarded growth, elevated body temperature, increased oxygen consumption and mild glycosuria. Lipid analysis of their carcasses revealed a reduced total lipid content which was accounted for largely in the neutral fat fraction. The cholesterol ester was the only fraction of the essential lipid which was decreased significantly. All of these effects of hyperthyroidism in the young rats were alleviated by a diet containing 30% cottonseed oil. The old rats were not as sensitive to thyroid feeding as the young rats and only the neutral fat fraction was modified. Young rats receiving thiouracil showed retarded growth, decreased body temperature and decreased oxygen consumption. The influence of thiouracil was more apparent on the high fat diet than on the low fat diet. Thiouracil feeding resulted in large increases in the percentage of total lipid deposited. This was accounted for largely in the neutral fat fraction. A small increase in the per cent of cholesterol esters was the only change observed in the “essential lipid” fraction under the experimental conditions used in this investigation. In general, the effects of induced hyperthyroidism were reversed in hypothyroidism. A high fat diet tended to alleviate the effects of increased thyroid activity but enhanced the characteristics of depressed thyroid activity.