HORMONAL IODINE IN THE DOG

Abstract

SUMMARY The nature and rate of formation of hormonal iodine in the dog has been studied by radioactive and chemical methods. A rapid appearance of protein-bound iodine (PBI) which was not extractable with acid butanol was noted during the first few hours after the administration of 131I. The butanol-insoluble fraction of PBI was not detectable 2–3 days after the dose when the residual activity was found to consist of approximately equal amounts of thyroxine and tri-iodothyronine. This unexpectedly high proportion of circulating tri-iodothyronine was checked by saturation analysis. It is suggested that relatively high levels of tri-iodothyronine in some dogs may in part account for the low PBI levels found in normal canine sera.