24 HOUR MELATONIN SECRETORY PATTERN IN CUSHING'S SYNDROME

The concentrations of plasma melatonin and cortisol were determined every 20 min during a 24 h period in 6 women aged 24 to 45 years with Cushing's syndrome of differing aetiologies (4 adrenal adenomas, 2 adrenal hyperplasia). Melatonin was assayed after chloroform extraction according to the method of Rollag and Niswender (1976). Abnormal melatonin secretory patterns were found in all the patients; 24 h melatonin concentration means varied from 130 to 413 pg/ml and were not significantly higher than the 24 h mean in 4 controls (215 ± 126 pg/ml). All six subjects however showed a significant increase of melatonin during the day period (302 ± 109 as compared with controls 129 ± 65 mg/ml, mean ± SD; P<0.005). No relationship could be found between abnormal melatonin levels and the sexual status of the patients (4 with amenorrhoea, 2 normally menstruating women). An alteration of melatonin secretory pattern is present in Cushing's syndrome, whatever the aetiology. It is suggested that hypercortisolism, by itself, may modify the pattern of melatonin secretion.