title: Seasonal variations of plasma gonadotropin, prolactin, and testosterone levels in primary and secondary hypogonadism: evidence for an independent testicular role.
abstract: BACKGROUND
  Seasonal hormonal rhythmicity of the hypothalamic-pituitary-gonadal axis may influence reproductive and sexual activity in mammals.
  
  
  OBJECTIVE
  To investigate whether pituitary-gonadal axis secretion seasonality occurs in men with primary and secondary hypogonadism and whether a hierarchical machinery regulates these variations.
  
  
  METHODS
  Six adult males with Klinefelter's syndrome (KS), eight with idiopathic normosmic hypogonadotropic hypogonadism (HH) and ten sex- and age-matched healthy controls were studied longitudinally for one year. Every three months, three plasma samples for assay of testosterone, LH, FSH, and prolactin were drawn and the mean value was used for statistical analysis.
  
  
  RESULTS
  Healthy males showed a significant seasonality in LH (zenith in spring) and testosterone (zenith in autumn) but not in FSH and prolactin concentrations. Patients with KS and those with HH showed a seasonal rhythmicity only of testosterone values, even if with small amplitude, with the zenith in spring and summer respectively.
  
  
  CONCLUSIONS
  The lack of dependence of testosterone on gonadotropin variations in normal men and the persistence of seasonal testosterone but not gonadotropin variations both in primary and secondary hypogonadism seem to indicate a possible independent testicular regulation of this seasonality. The shift of testosterone peak in hypogonadal men with respect to controls suggests that LH variations could play a synchronizing, rather than pace-making, role in seasonal testosterone variations. Since hormonal seasonality may also influence gonadal activity in humans, replacement therapy in hypogonadism should be aimed also at restoring a normal seasonal rhythmicity of pituitary-gonadal hormone concentrations.
authors.affiliation: Department of Cardio-Thoracic and Respiratory Sciences, Second University of Naples, Via Pansini 5, 80131 Naples, Italy. gbellastella@hotmail.com
authors.forename: G
authors.initials: G
authors.lastname: Bellastella
authors.forename: E
authors.initials: E
authors.lastname: Pane
authors.forename: S
authors.initials: S
authors.lastname: Iorio
authors.forename: A
authors.initials: A
authors.lastname: De Bellis
authors.forename: A A
authors.initials: AA
authors.lastname: Sinisi
mesh_terms: D000328:Adult; D043373:Follicle Stimulating Hormone, Human / Q000097:blood*; D006801:Humans; D007006:Hypogonadism / Q000097:blood* / Q000209:etiology; D007558:Italy; D007713:Klinefelter Syndrome / Q000097:blood; D008137:Longitudinal Studies; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D011388:Prolactin / Q000097:blood*; D012621:Seasons; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D043373:Follicle Stimulating Hormone, Human; D013739:Testosterone; D011388:Prolactin; D007986:Luteinizing Hormone