A multinational study of the relationships between nighttime urinary melatonin production, age, gender, body size, and latitude

Overnight urines were collected each month for 12-16 months from 321 normal subjects at 19 medical centers in 14 countries distributed on 5 continents at latitudes from 31 01 South to 77 00 North. Mean melatonin concentration was found to negatively correlate with age, weight, and height. When the s exes were considered separately melatonin only correlated with age for fema le and with age and weight for males. A weak correlation with latitude, but not longitude, was also found.