Effect of cold-exposure on serum thyrotrophin levels in man.

Serum TSH levels were measured after exposing male volunteers to cold, or successively to warmth and to cold, causing clear changes in body temperature. Very moderately heated Finnish sauna bath increased body temperature to about an average of 39 degrees C, and cooling in a relatively warm swimming pool (+25 to +28 degrees C, 30 min) decreased body temperature to below 35 degrees C after sauna, and to about 33 degrees C without sauna. In both cases a slight but significant initial increase of serum TSH was demonstrated. No changes in serum T3 or ETR were seen. The results suggest that a similar mechanism of initial TSH response may exist in humans as has previously been demonstrated in rats.