Circannual prolactin rhythms: calendar-like timer revealed in the pituitary gland

Trends Endocrinol Metab. 2007 Sep;18(7):259-60. doi: 10.1016/j.tem.2007.07.001. Epub 2007 Aug 6.


Although photoperiodic regulation of annual rhythms in reproduction and other functions has been well characterized, the basis for the endogenous generation of circannual rhythms during exposure to constant conditions has not been elucidated. Lincoln and colleagues have recently reported that circannual prolactin rhythms in rams persist after hypothalamo-pituitary disconnection, but not after pinealectomy. Does the pars tuberalis, the site of pituitary gland melatonin receptors, generate circannual rhythms and integrate photoperiodic signals mediated by melatonin?

Publication types

  • Review

MeSH terms

  • Animals
  • Circadian Rhythm / physiology*
  • Melatonin / metabolism
  • Melatonin / physiology
  • Photoperiod
  • Pineal Gland / metabolism
  • Pineal Gland / physiology
  • Pituitary Gland, Anterior / metabolism
  • Pituitary Gland, Anterior / physiology*
  • Prolactin / metabolism
  • Prolactin / physiology*
  • Time Factors


  • Prolactin
  • Melatonin