Diurnal hypersecretion of growth hormone in depression

A 24-h profile of plasma GH concentrations was obtained together with polygraphic recordings of sleep in 16 men suffering from a major depressive disorder (8 unipolar and 8 bipolar) and in 8 age- and sex-matched normal men. None of the patients had any physical illness. All were studied after a drug-free period of at least 15 days. Blood was sampled every 15 min. The amount of GH released in every significant secretory spike was estimated using a computer program. Both unipolar and bipolar depressed patients secreted more GH than normal men (mean +/- SD, 441 +/- 189 micrograms/24 h for unipolar depressed men; 357 +/- 143 micrograms/24 h for bipolar depressed men vs. 172 +/- 101 micrograms/24 h for normal men (P less than 0.01). This hypersecretion occurred during waking hours rather than during sleep. The increase in daytime GH release was more marked in unipolar depressed patients. During sleep, depressed patients and normal men secreted similar amounts of GH despite an overall reduction in slow wave stages in depressed patients. An early sleep GH increase was found in all but one of the normal men, but was absent in seven of the eight unipolar depressed patients, who had, instead, a presleep increase in between 2100-0000 h. No consistent disturbance of the temporal association between sleep onset and GH secretion was found in bipolar depressed patients.