Disturbed circadian variation of serum thyrotropin in patients with endogenous depression.

The relationship between the degree of depression and the circadian variation of serum TSH, T3 and T4 was investigated in 19 endogenously depressed patients. The difference between the hormone concentrations at 2 p.m. and at 12 p.m. was taken as an estimate of the magnitude of circadian variation. It was found that the circadian variation in serum TSH was inversely related to the degree of endogenous depression. This was mainly due to a diminution or absence of the night increase of TSH in severely depressed patients. A circadian variation of serum free T3 was found in the less depressed patients whereas no diurnal change was found in serum free T4. In severely depressed patients there were no significant diurnal changes in free thyroid hormone concentrations. The results indicate a hypothalamic dysfunction in manic-depressive psychosis.