Age and diet effect on thyroid-serum ratio, PBI, and thyroidal iodine and histology in rodents

¹ National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland

The thyroid-serum (T/S) ratio and relative thyroid weight of rats made obese by high fat diet were lower, absolute thyroid weight and thyroidal iodine concentration higher, and thyroid follicles larger and more filled with colloid than in rats on control diet. There was a tendency in rats and mice for the T/S ratio to reach a peak value at 10–18 weeks of age which was not observed in rats on a high fat diet. Rats at 4–5 weeks of age tended to have a relatively larger thyroid, lower T/S ratio, and lower thyroidal idoine concentration than older animals.