title: Acromegaly without imaging evidence of pituitary adenoma.
abstract: BACKGROUND
  GH-secreting pituitary adenomas are nearly always visible on conventional magnetic resonance (MR) imaging. However, management and outcome of acromegalic patients lacking imaging evidence of GH-secreting pituitary adenomas are undefined.
  
  
  OBJECTIVE
  The aim was to evaluate surgical exploration for MR-invisible GH-secreting pituitary adenomas.
  
  
  METHODS
  We conducted a retrospective review at two tertiary care centers.
  
  
  METHODS
  Consecutive acromegalic patients without imaging evidence of a pituitary adenoma on pre- and postcontrast, spin echo T1-weighted MR imaging and who lacked evidence of an ectopic (nonpituitary) source causing GH excess were included.
  
  
  METHODS
  Surgical exploration with identification and resection of a pituitary adenoma was performed.
  
  
  METHODS
  Laboratory values (GH, IGF-I), surgical findings, and clinical outcome were analyzed.
  
  
  RESULTS
  Six patients (three males, three females; 3% of all patients) with suspected GH-secreting adenomas did not demonstrate imaging evidence of pituitary adenoma on conventional MR imaging. Three patients underwent a postcontrast, volumetric interpolated breath-hold examination MR-imaging sequence (1.2-mm slice thickness), which revealed a 4-mm pituitary adenoma not seen on the spin echo T1-weighted MR imaging in one patient. A pituitary adenoma was identified and removed in all patients (mean diameter, 5.6 mm; range, 5 to 6.7 mm). Histological analysis confirmed that the lesions were GH-secreting adenomas. All patients achieved biochemical remission after surgical resection.
  
  
  CONCLUSIONS
  Acromegaly can be caused by GH-secreting pituitary adenomas that are not evident on conventional MR imaging. Adenomas in some of these patients become evident using volumetric interpolated breath-hold examination MR imaging. Surgical exploration of the pituitary gland in acromegalic patients with endocrine findings consistent with a GH-secreting adenoma but negative MR imaging can lead to identification and removal of an adenoma.
authors.affiliation: Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Building 10, Room 3D20, Bethesda, Maryland 20892-1414, USA. lonserr@ninds.nih.gov
authors.forename: Russell R
authors.initials: RR
authors.lastname: Lonser
authors.forename: Bogdan A
authors.initials: BA
authors.lastname: Kindzelski
authors.forename: Gautam U
authors.initials: GU
authors.lastname: Mehta
authors.forename: John A
authors.initials: JA
authors.lastname: Jane
authors.forename: Edward H
authors.initials: EH
authors.lastname: Oldfield
mesh_terms: D000172:Acromegaly / Q000000981:diagnostic imaging* / Q000209:etiology; D000236:Adenoma / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005188:False Negative Reactions; D005260:Female; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000150:complications / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies; D047368:Tumor Burden