Influence of thyroid hormone treatment on growth, body composition and metabolism during cold stress in genetically obese mice

Abstract

Pharmacologic doses of thyroid hormones were administered chronically in diets and acutely by injection to determine their metabolic effects on the development of obesity and the response to cold stress in genetically obese mice. Feeding a 0.1% thyroid powder (TP) diet for 6 weeks to weanling male mice resulted in a marked reduction in weight gain and high mortality in obese but not in non-obese mice. Diets containing 0.01 and 0.02% TP also produced enhanced effects in obese mice during a 13-week feeding period as indicated by reduced body weight, fat and protein and reduced blood glucose at ambient temperature. Both acute and chronic treatment with thyroid hormone produced similar effects in the cold (4°). Blood glucose concentrations were reduced in both obese and non-obese mice, but blood free fatty acid values were unchanged due to hormone treatment. Neither acute nor chronic treatment with thyroid hormones prolonged survival of obese mice during cold exposure. These results suggest a normal or enhanced fat mobilization and utilization in response to exogenous thyroid hormone at ambient temperature. However, the defect in utilization of energy stores for thermogenesis during cold exposure was not ameliorated by this treatment.