title: Acromegaly with normal basal growth hormone levels.
abstract: BACKGROUND
  The most common cause of acromegaly is excess of growth hormone (GH) secretion.
  
  
  METHODS
  We report a 42-year-old male patient, who had become acromegalic over the past 5 years. There were no visual changes or change in sexual function, no gynaecomastia or galactorrhoea. Both CT and MRI scans showed a large mass measuring 2.5 x 2.5 x 3.5 cm, originating from the sella turcica and extending into and totally filling up the sphenoid sinus with diffusely invasive features.
  
  
  RESULTS
  Basal serum GH level was within normal range, but insulin-like growth factor 1 (IGF-1) was elevated with slightly increased prolactin (PRL) and impaired GH secretory regulation as well. A pituitary adenoma was partially removed through transsphenoidal microsurgery. Pathology confirmed a mammo-somatotrophic adenoma but immunocytochemistry study of the tumour showed only positivity for PRL but not GH.
  
  
  CONCLUSIONS
  When acromegaly occurs without GH level elevation, one should pay attention that: 1) IGF-1 might be the cause of the clinical feature of acromegaly; 2) The tumour might undergo morphological transformation; and 3) Hyperinsulinemia or GH receptor antibody formation could also be the cause of the acromegalic appearance.
authors.affiliation: Division of Neurosurgery, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montréal, Québec, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Mohr
authors.forename: Z P
authors.initials: ZP
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Schweitzer
mesh_terms: D000172:Acromegaly / Q000097:blood / Q000209:etiology / Q000473:pathology*; D000328:Adult; D005951:Glucose Tolerance Test; D013006:Growth Hormone / Q000097:blood*; D006728:Hormones / Q000097:blood; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010911:Pituitary Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D015175:Prolactinoma / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology*; D013973:Thyrotropin-Releasing Hormone / Q000097:blood; D014057:Tomography, X-Ray Computed
chemical_list: D006728:Hormones; D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone