Circannual cycle in plasma testosterone levels in man.
In a groups of 15 healthy male subjects a statistically significant circannual cycle in plasma testosterone levels was assessed by sampling blood at 3-monthly  intervals. Peak levels were found in summer and early autumn and a nadir in the winter and early spring.
D000328:Adult; D006801:Humans; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D012621:Seasons; D013739:Testosterone / Q000097:blood*
D013739:Testosterone