SULPHATOXYMELATONIN EXCRETION IN OLDER-PEOPLE - RELATIONSHIP TO PLASMA MELATONIN AND RENAL-FUNCTION

In order to validate measurement of urinary sulphatoxymelatonin as an accurate method of estimating plasma melatonin secretion in older peop le, we compared 24 h plasma melatonin secretion and sulphatoxymelatoni n excretion with renal function in 20 subjects 62-89 years of age. The re was a good correlation between plasma and urinary sulphatoxymelaton in over the same 24 h period (R-2 = 0.797) and no relationship between creatinine clearance and sulphatoxymelatonin excretion (R-2 = 0.075). The results suggest that sulphatoxymelatonin excretion estimation is a good surrogate measurement of plasma melatonin secretion in older pe ople, at least across the range of creatinine clearance for the subjec ts in the study, 0.41-1.81 ml/sec.