Abnormal serum melatonin levels in patients with intrasellar tumors.

Melatonin, a pineal indoleamine, is postulated to be of importance in a regulatory fashion in hypothalamic and pituitary function. Attempts to utilize its random serum level as a consistent marker of pineal tumors have not been successful. Fifteen patients were studied to determine whether the normal diurnal variation in serum melatonin as determined by radioimmunoassay was altered by the presence of an intrasellar pituitary region tumor. A normal diurnal cycling of melatonin (high level at night, low level at midday coupled to the light-dark cycle) was seen in controls consisting of patients admitted for spinal or supratentorial procedures (a.m. melatonin, 15.4 +/- 3.7 pg/ml; p.m. melatonin, 57.1 +/- 16.3 pg/ml). This normal pattern of melatonin levels was altered in the group of patients with intrasellar tumors (a.m. melatonin, 28.9 +/- 6.7 pg/ml; p.m. melatonin, 28.4 +/- 7.3 pg/ml). Hospitalization and operation caused nonspecific alterations in the pattern of melatonin in both groups. These results suggest that the pattern of secretion rather than the absolute midday value of melatonin may be of greater importance as evidence of altered pineal and pituitary neuroendocrine regulation.