Effect of iodine intake and food consumption.

Rats were exposed to cold (4 degrees C) for 1 and 4 weeks. The T4 plasma concentrations initially declined (24.5 +/- 7.7 nmol/l) after 1 week but returned to normal levels after 4 weeks (52.9 +/- 14.2 nmol/l). The T3 concentrations were elevated after both 1 and 4 weeks at 4 degrees C (1.31 +/- 0.21 and 1.38 +/- 0.12 nmol/l, respectively). Control values (23 degrees C) for T4 were 42.6 +/- 10.3 and for T3 1.11 +/- 0.13 nmol/l. Addition of 0.015 g KI/l to the drinking water prevented the T4 decrease in plasma after 1 week of cold exposure. No effect of iodide was observed at 23 degrees C. The suppletion of KI did not change pattern of T3 increase after cold exposure. After 4 weeks of cold exposure the T4 levels of the iodide-supplemented animals did not differ from the non-sulemented group. No evidence was found that increased food intake is a contributory factor in the development leading to increased T3 plasma levels during cold exposure.