Thyroid function in various strains of mice: T/S ratio, PBI and thyroid weight

¹ National Institute of Arthritis and Metabolic Diseases and Division of Research Services, National Institutes of Health, Bethesda, Maryland
² National Institute of Arthritis and Metabolic Diseases and Division of Research Services, National Institutes of Health, Bethesda, Maryland Research Services, National Institutes of Health, Bethesda, Maryland

Strain differences were observed in the T/S ratios and thyroid weights of 505 mice comprising six inbred strains and three pairs of F₁ hybrids. These differences were not accounted for by variations in body weight or degree of blocking of iodine incorporation into organic compounds by Tapazole. There was an apparently inverse relationship between the mean T/S ratios of the various strains and the relative weights of the thyroid glands. The weights of the thyroid glands increased progressively from 7 to 16 months of age in each strain even though there were only small changes in body weight. The T/S ratios were relatively unchanged between these ages. The weight of the thyroid gland appeared to be influenced by the interaction between the strain of animal, diet fed and possibly by obesity. The mean plasma PBI values ranged from 0.9 to 3.5 µg/ml and showed no relationship to the T/S ratios.