title: Pilot study of circulating prolactin levels and endothelial function in men with hypertension.
abstract: BACKGROUND
  Hyperprolactinemia has been recently associated with hypertension and endothelial dysfunction in humans, confirming animal studies performed in the 1970s that showed high prolactin levels to exert positive chronotropic and vasoconstrictive effects. Whether prolactin affects endothelial function, in the absence of hyperprolactinemia, remains unknown. Considering that secretion of prolactin presents circadian rhythmicity, we tested the hypothesis that in patients with hypertension, who present diurnal variation in their endothelial function as well, prolactin levels correlate with endothelial function and/or blood pressure.
  
  
  METHODS
  Endothelial function, assessed by flow-mediated dilatation (FMD) and serum prolactin were examined successively at 12 PM, 9 PM, and 7 AM in 27 nonhyperprolactinemic men with newly diagnosed, untreated essential hypertension.
  
  
  RESULTS
  Both FMD and prolactin presented 24-h variation (P < 0.01). FMD reached its lowest values at 7 AM (2.1 ± 1.8%, mean ± s.d.); concurrently prolactin levels peaked (7.18 ng/ml, median). Across the three time points, prolactin changes inversely interacted with FMD changes (P = 0.002). Systolic and diastolic blood pressure also varied significantly but no interaction with prolactin changes was evident.
  
  
  CONCLUSIONS
  Diurnal fluctuations of prolactin levels are associated with decreased endothelial function that occurs early in the morning in men with hypertension, although this study did not assess causality. Additional studies are required to determine whether these responses differ from normotensive individuals.
authors.affiliation: Vascular Laboratory, Department of Therapeutics, Alexandra Hospital, Athens University Medical School, Greece. stamatelopoulosk@yahoo.gr
authors.forename: Kimon S
authors.initials: KS
authors.lastname: Stamatelopoulos
authors.forename: Georgios A
authors.initials: GA
authors.lastname: Georgiopoulos
authors.forename: Petros P
authors.initials: PP
authors.lastname: Sfikakis
authors.forename: Georgios
authors.initials: G
authors.lastname: Kollias
authors.forename: Efstathios
authors.initials: E
authors.lastname: Manios
authors.forename: Emily
authors.initials: E
authors.lastname: Mantzou
authors.forename: Katerina
authors.initials: K
authors.lastname: Kyrkou
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Zakopoulos
authors.forename: Christos M
authors.initials: CM
authors.lastname: Papamichael
authors.forename: Maria
authors.initials: M
authors.lastname: Alevizaki
mesh_terms: D000328:Adult; D001794:Blood Pressure; D002940:Circadian Rhythm; D004730:Endothelium, Vascular / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011388:Prolactin / Q000097:blood* / Q000502:physiology; D014664:Vasodilation
chemical_list: D011388:Prolactin