Studies with mouse pituitary thyrotropic tumors, iii. Diiodotyrosine, monoiodotyrosine ratio in the hyperfunctioning thyroid of mice bearing implants of an autonomous nonresponsive strain.

Studies have been made of thyroid function in mice bearing an autonomous nonresponsive thyrotropin-producing transplantable tumor. The evidence indicates that the gland was rendered hyperfunctioning. Injected Nal131 disappeared more rapidly from the blood of tumor bearing mice than from normal controls, and was collected in larger amounts by the thyroid. Labeled iodothyronines appeared in the serum earlier in the tumor bearing mice than in the controls, whereas exogenous thyrotropin given for a brief period of time to healthy mice did not produce this effect. An unusually high DIT: MIT ratio was found in the thyroid of tumor-bearing mice fed on a diet adequate in iodine. This value was not equalled in the thyroids of healthy mice given short-term treatment with thyrotropin.