title: Role of melatonin in nocturnal prolactin secretion in women with normoprolactinemia and mild hyperprolactinemia.
abstract: OBJECTIVE
  Our objective was to clarify the relationship between the nocturnal melatonin surge and the nocturnal prolactin release in women with normoprolactinemia and mild hyperprolactinemia.
  
  
  METHODS
  Nocturnal serum melatonin and prolactin levels were determined for a various awake/sleep and light/dark conditions in a total of 23 healthy normoprolactinemia and 9 mild hyperprolactinemia. Patterns of prolactin and melatonin levels were subject to analysis of variance.
  
  
  RESULTS
  During sleep deprivation under continuous illumination in normoprolactinemia, neither melatonin nor prolactin increased in concentration. In contrast, during sleep deprivation in a dark environment, both hormones were increased. The maximal prolactin levels in mild hyperprolactinemia under physiologic sleep/dark were significantly higher (p < 0.01) and were reached 2 hours earlier than in normoprolactinemia. However, each woman with mild hyperprolactinemia had similar melatonin surges. Oral administration (1 mg) of melatonin to normoprolactinemia and mild hyperprolactinemia in the daytime resulted in release of prolactin in a fashion similar to that observed during the night.
  
  
  CONCLUSIONS
  Melatonin can regulate nocturnal prolactin secretion independent of sleep-related factors. Furthermore, the nature of the response to exogenous melatonin administration suggests that mild hyperprolactinemia may be unusually sensitive to melatonin.
authors.affiliation: Department of Obstetrics and Gynecology, Kochi Medical School, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Okatani
authors.forename: Y
authors.initials: Y
authors.lastname: Sagara
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D003624:Darkness; D005260:Female; D006801:Humans; D006966:Hyperprolactinemia / Q000503:physiopathology*; D008027:Light; D008550:Melatonin / Q000097:blood / Q000502:physiology; D011388:Prolactin / Q000378:metabolism*; D012892:Sleep Deprivation
chemical_list: D011388:Prolactin; D008550:Melatonin