The daily profile of plasma melatonin in obese and Prader-Willi syndrome children.

Daily plasma melatonin profiles were determined by RIA in exogenously obese and Prader-Willi syndrome children. The melatonin RIA was validated for use in human plasma by evaluating melatonin immunoreactivity in the resultant eluate fractions of a high performance liquid chromatogram of a chloroform-extracted pooled human plasma sample. Melatonin immunoreactivity in the plasma profile occurred only in the fraction that corresponded to the chromatographic position of authentic melatonin. Exogenously obese patients had plasma melatonin profiles characterized by low levels during the day (20-30 pg/ml plasma) and high levels at night (65-130 pg/ml plasma). The plasma melatonin profile did not vary as a function of weight or pubertal status. Prader-Willi syndrome patients had similar melatonin profiles to those of exogenously obese patients. Although the Prader-Willi children had a delayed onset of puberty, the plasma melatonin profile was unaltered. These data indicate that plasma melatonin may not play a role in the onset of puberty. However, the daily melatonin profile is a temporally precise hormonal rhythm in humans.