Effects of febrile and epileptic convulsions on daily variations in plasma melatonin concentration in children.

Plasma melatonin was measured in 118 infants and children (39 controls, 28 with epileptic convulsions, and 51 with febrile convulsions). The control group displayed a typical circadian rhythm, with melatonin peaking between 0200 and 0400. This normal daily variation significantly changed in the epileptic group, which showed a characteristic phase-advance, with the nocturnal melatonin peak appearing between 2400 and 0200. Febrile convulsions were associated with the disappearance of the normal circadian rhythm of melatonin, which was replaced by melatonin bursts throughout the light:dark cycle. In both febrile and epileptic children, melatonin levels were significantly increased in comparison with normal children.