Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study

Ruhayel Y, Malm G, Haugen TB, Henrichsen T, Bjorsvik C, Grotmol T, Saether T, Malm J, Figenschau Y, Rylander L, Levine RJ, Giwercman A. Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study. Clin Endocrinol (Oxf) 2007; 67(1):85-92.