EFFECT OF FREQUENT HOUSING CHANGES AND OF MUSCULAR EXERCISE ON THE THYROID GLAND OF MICE1

Abstract

The possibility that the psychological stimulation resulting from frequent changes of housing might have an effect on the thyroid was investigated in mice "transferred" daily to different types of cages for a period of 8 weeks. Similarly, the effect of forced muscular exercise was investigated in mice made to walk daily 3 1/2 to 4 hours in a rotating cage for a period of 8 weeks. All animals were fed controlled diets with low or adequate levels of dietary iodine. Control mice on the low iodine diet had enlarged thyroids showing histological signs of stimulation. "Transferred" or exercised mice fed the same diet failed to show thyroid stimulation. Thus, frequent housing changes and forced muscular exercise prevented the thyroid stimulation resulting from iodine deficiency. This depressing effect on the thyroid does not appear to be due to unspecific stress, since adrenal weight was not altered.