Increased 131I uptake by the thyroid glands of Obese strain (OS) chickens derived from non-Protamone-supplemented hens.

The Obese strain (OS) of chickens spontaneously develops autoimmune thyroiditis several weeks after hatching, characterized by severe lymphoid infiltration and circulating thyroglobulin antibody. Sundick & Wick (1974) found that the thyroid glands of OS embryos and newly hatched chicks actually incorporated more I than normal controls when the parents of both groups were fed a Protamone-supplemented diet. Since this material—an iodinated casein containing thyro-active substances—drastically reduced thyroidal uptake of I, several experiments were designed to compare OS and normal chicks free from these effects. In the first experiment the dietary supplementation of OS and normal hens were changed from Protamone to pure thyroxine and triiodothyronine. Their eggs were collected daily and incubated. The hatched chicks were tested for 20-hr I uptake and it was determined that 11–18 days after the food switch, the inhibition of uptake by Protamone was reversed, and the newly hatched OS chicks still had a significantly increased 20-hr I uptake when compared to the normal controls. Comparison of the offspring of a special flock of OS hens that lays without hormonal supplementation, with the parental Cornell C strain from which the OS is derived, similarly revealed a higher 20-hr I uptake by the OS (<0·005). The increased thyroidal uptake of OS was apparent as early as 4 hr after I administration and seemed to be independent of slight variations in the amount of I available to the chicks, and also seemed to be independent of maternally derived thyroglobulin antibody vertically transferred into OS chicks. These results suggest that an abnormality of the OS thyroid gland might be a prerequisite for the spontaneously occurring autoimmune thyroiditis in this strain.