Daily variation in the concentration of melatonin and 5-methoxytryptophol in the human pineal gland: effect of age and Alzheimer's disease.

Melatonin and 5-methoxytryptophol (ML) were measured in human pineals (38 controls, 16 subjects with Alzheimer's disease). Time of death had a major influence on the indole concentrations with significantly higher melatonin levels occurring at night (22.00-10.00 h) and significantly higher ML levels occurring during the day (10.00-22.00 h). This daily variation disappeared in both the older subjects (55-92 years) and in the Alzheimer patients (55-89 years).