Plasma cortisol concentrations in patients with different circadian pain rhythm.

Plasma cortisol concentration was measured 4 times in a 24 h period in 4 groups of patients. Thirty of them complained of pain with different circadian rhythmicity (nocturnal pain, diurnal pain, continuous pain) and 10 were pain-free and served as a control group. The mean plasma cortisol concentration was significantly higher in pain patients as compared with healthy, pain-free subjects at the time of the highest pain intensity. There is a positive correlation between the intensity of pain and increased plasma cortisol level and this disagrees with previous reports of a relationship of pain and lower blood cortisol levels.