[Melatonin secretion in Klinefelter's syndrome].

It has been observed that the pineal gland seems to modulate diencephalic neuroendocrine activity through its principal hormone, melatonin. In animals, melatonin inhibits the secretion and release of hypophyseal gonadotropins, probably by inhibiting hypothalamic releasing factors; in man, on the contrary, the administration of LHRH seems to have a stimulating effect on melatonin serum levels. In the light of this, in pathologies characterised by an imbalance in the hypothalamus-hypophyseal-gonad axis, it is possible to hypothesise variations in the secretion of melatonin and/or in its circadian fluctuations. In order to clarify further the relationship between the epiphysis and the hypothalamus-hypophyseal axis, the present study evaluated the pattern of melatonin secretion in a group of 16 patients with Klinefelter's syndrome. The circadian rhythm of melatonin secretion was determined from venous blood samples taken at 9 am, 1 pm, 5 pm, 9 pm, 1 am and 5 am; the same protocol was also followed in two control groups of respectively prepuberal and puberal healthy subjects. During the night samples were taken as rapidly as possible, using a red light source in order to not interfere with melatonin secretion. All of the examinations were performed during the winter period. Serum levels of melatonin were determined, after extractions with diethylether, by means of a double antibody RIA using commercially available kits (Bioscience Product--The Netherlands). Intra- and inter-assay coefficients of variation were respectively 3% and 8%. The data are reported as mean values +/- SD; the results were analysed by means of Student's test for unpaired data and analysis of variance.(ABSTRACT TRUNCATED AT 250 WORDS)