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J. Rosen, R. B. Rosen, D.-N. Hu, K. Tai, M. Chen, S. McCormick, J. B. Walsh; Reduced Melatonin Levels in Age-Related Macular Degeneration Patients as Measured by Urinary 6-Sulfatoxymelatonin Level. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3423.
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Melatonin, an endogenous neurohormone produced by the pineal gland and the retina, is a potent antioxidant and free radical scavenger, and can suppress abnormal upregulation of VEGF by RPE cells. The purpose of the present study was to compare peak melatonin levels in age-related macular degeneration (AMD) patients and normal controls. In order to capture peak melatonin levels, which occur late at night, and avoid the need for hospitalization, in order to collect properly timed blood specimens, melatonin levels were determined by measuring urinary 6-sulfatoxymelatonin (the main metabolite of melatonin) level, which correlates well with the melatonin level in the blood.
The first urine of the morning was collected from 20 AMD patients (10 cases of dry type and 10 cases of wet type) and gender/age matched 10 normal controls. Subjects were carefully screened to exclude individuals on confounding medications or with confounding genito-urinary conditions or ocular conditions and instructed to refrigerate specimens at home as soon as collected. Specimens were stored under -70 C until measurement which was performed in batch. Level of 6-sulfatoxymelatonin in specimens was measured by a commercial 6-sulfatoxymelatonin ELISA kit (ALPCO Diagnostics, Windham, NH).
The levels of urine 6-sulfatoxymelatonin (mean ± SD) in dry type AMD, wet type AMD, and normal control were 7.1 ± 5.8, 8.3 ± 9.3 and 12.2 ± 9.7 ng/ml, respectively. In spite of apparent reduced average levels in the AMD groups, Student t-test analysis showed a non-significant difference between the normal control and the AMD groups (P = 0.11).
Urine 6-sulfatoxymelatonin levels in AMD patient measured 30- 40% lower than those of normal controls. This difference between AMD and control subjects, however, was not statistically significant, perhaps due to the relatively small sample size. Currently, recruitment is ongoing to enlarge the subject pool in the hope of clarifying melatonin level differences which may help to reveal its possible role in the pathogenesis of AMD.
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