<i>Study design</i>: Crossover double blind, randomized placebo-controlled trial.<p> <p><i>Objectives</i>: Circadian oscillators are located both in the brain and in peripheral organs. Melatonin, the main brain-derived hormone governing circadian variations, is highly associated with daylight patterns. However, in subjects with tetraplegia the melatonin levels are blunted. Here we studied peripheral ...