PITUITARY-THYROID FUNCTION IN THE C57 BL/KSJ DB/DB DIABETIC MOUSE.
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PublisherThe University of Arizona.
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AbstractThe C57 BL/KsJ db/db mouse is obese, hyperglycemic, hyperinsulinemic and serves as a model for noninsulin dependent diabetes mellitus (NIDDM). This study reports a dysfunction in the pituitary-thyroid axis and apparent peripheral resistence to thyroid hormones due to a reduction in T3 receptor binding. Diabetic mice have subnormal serum T4 concentrations and supranormal T3 concentrations which are most pronounced between 8 and 10 weeks of age. Thyroid glands of diabetic animals appear hypoactive histologically. Serum TSH concentrations approximate those found in normal mice. In vitro studies show that thryroid glands from diabetic animals are responsive to TSH. Pituitary glands from the same animals hypersecrete TSH and are responsive to TRH. Ultrastructural analysis of pituitary thyrotropes from diabetic mice indicate that these cells are hypersecretory and may be under chronic stimulation by TRH. Diet restriction maintains diabetic mice at a normal total body weight but these animals still possess abnormally large fat deposits. The thyroid hormone profile of these mice appears normal as does the histological appearance of the thyroid gland. Similarly, the blockade of peripheral deiodination by daily injection of iopanoic acid returns the thyroid hormone profile to normal.
Degree ProgramGraduate College