Melatonin concentrations in human serum, ventricular and lumbar cerebrospinal fluids as an index of the secretory pathway of the pineal gland.

Melatonin was extracted from human sera, ventricular and lumbar cerebrospinal fluids taken within an hour from 25 patients undergoing neurosurgical operations such as ventricular shunts and craniotomy. Using a radioimmunoassay procedure, it was possible to measure the melatonin concentrations in 3 groups of patients: (a) those with obstructive hydrocephalus, (b) those with communicating hydrocephalus, and (c) those with normal cerebrospinal fluid flow. It was demonstrated that melatonin levels were higher in sera compared with those in lumbar and ventricular cerebrospinal fluids thus supporting the view that melatonin is primarily secreted into the bloodstream.