title: The pituitary in klinefelter syndrome.
abstract: BACKGROUND
  Klinefelter syndrome is a genetically determined primary gonadal defect characterized by the XXY karyotype. The testes are small, blood testosterone levels are low, and blood gonadotropin levels are elevated. Pituitary changes in patients with Klinefelter syndrome have not been evaluated in detail.
  
  
  METHODS
  The first patient, a 76-yr-old man, was operated for a large sellar mass. The second and third patients, a 62- and a 52-yr-old man, respectively, died of cardiac failure. Both the latter pituitaries were normal-sized and removed at autopsy. The diagnosis of Klinefelter syndrome was confirmed by genetic testing in all three cases. The formalin-fixed and paraffin-embedded pituitaries of three patients were evaluated for adenohypophysial hormone immunoreactivity. For immunohistochemistry, the streptavidin- biotin-peroxidase (ABC) complex method was applied.
  
  
  RESULTS
  In case 1, histology and immunohistochemistry revealed an oncocytic gonadotroph macroadenoma immunoreactive for FSH and alpha subunit. No pituitary gland was evident. The pituitary of case 2 featured hyperplasia of gonadotrophs, some with features of "gonadal deficiency cells," and a microadenoma immunoreactive for GH. The pituitary of case 3 similarly showed hyperplasia of gonadotrophs and the formation of gonadal deficiency cells.
  
  
  CONCLUSIONS
  Protracted stimulation of gonadotrophs due to lack of androgen feedback might have been a factor in the formation of the gonadotroph adenoma in case 1 and in the development of gonadotroph hyperplasia in cases 2 and 3. The clinically silent GH microadenoma of case 2 was regarded as an incidental finding.
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA. scheithauer.bernd@mayo.edu
authors.forename: B W
authors.initials: BW
authors.lastname: Scheithauer
authors.forename: M
authors.initials: M
authors.lastname: Moschopulos
authors.forename: K
authors.initials: K
authors.lastname: Kovacs
authors.forename: B S
authors.initials: BS
authors.lastname: Jhaveri
authors.forename: T
authors.initials: T
authors.lastname: Percek
authors.forename: R V
authors.initials: RV
authors.lastname: Lloyd
mesh_terms: D000236:Adenoma / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D000368:Aged; D006801:Humans; D006965:Hyperplasia / Q000209:etiology / Q000473:pathology; D007150:Immunohistochemistry; D007713:Klinefelter Syndrome / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010900:Pituitary Diseases / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D010908:Pituitary Hormones, Anterior / Q000096:biosynthesis; D010911:Pituitary Neoplasms / Q000209:etiology / Q000378:metabolism / Q000473:pathology*
chemical_list: D010908:Pituitary Hormones, Anterior