[Annual endocrine rhythms in man].

Biological rhythms spread over a wide range of frequencies: circadian, ultradian and infradian. Circannual rhythms belong to this latter domain as their period average one year +/- 2 months. The seasonal rhythms in man of melatonin, prolactin, hormones of bone metabolism, ACTH and HCG are here reviewed and the questions raised by their characterization - including methodological problems - their origin and their incidence on health and diseases.