title: "Micromegaly": an update on the prevalence of acromegaly with apparently normal GH secretion in the modern era.
abstract: OBJECTIVE
  Approximately 25 % of cases of clinically active acromegaly cases treated in our academic center between 1996 and 2000, were diagnosed in patients who had elevated plasma IGF-1 levels, but apparently "normal" 24-h mean plasma GH levels. The current study served to update the data for patients with acromegaly referred to our facility, after increasing awareness of this "normal" GH subpopulation throughout the medical community.
  
  
  METHODS
  A retrospective chart review was conducted on 157 patients with acromegaly who underwent resection of a confirmed somatotroph pituitary adenoma at the University of Michigan Health System between the dates of 1 Jan 2001 to 23 Sept 2015.
  
  
  RESULTS
  Overall prevalence of acromegalic patients with "normal" GH levels, defined as GH <4.7 ng/mL, was 31 %. Over time, the percentage of patients with "normal" GH at diagnosis did not decline: 26 % from 2001 to 2005, 19 % from 2006 to 2010, and 47 % from 2011 to 2015. Mean pituitary tumor size was 1.8 ± 0.1 cm for the group with elevated GH, and 1.2 ± 0.1 cm for the group with "normal" GH (p < 0.001). Percent microadenomas was higher in a group with "normal" GH as compared to those with elevated GH (48 vs. 12 %, p < 0.001), and tumors >2 cm in the maximal diameter were encountered more frequently in the group with elevated GH (43 vs. 14 %, p < 0.001).
  
  
  CONCLUSIONS
  Our data show that a substantial percentage of patients with clinical acromegaly have "normal" GH, and therefore strengthens the growing body of evidence which supports the leading role of IGF-1 levels in diagnostic evaluation. At the present time, questions about the natural course of "micromegaly" and treatment benefits compared to the subpopulation with elevated GH levels remain unanswered, but research continues to build on our understanding of the heterogeneous population of individuals.
authors: Division of Metabolism, Endocrinology, and Diabetes, Internal Medicine Department, University of Michigan, 24 Frank Lloyd Wright Drive, G-1500, P.O. Box 482, Ann Arbor, MI, 48106, USA.
authors: Laura B
authors: LB
authors: Butz
authors: Department of Neurosurgery and the Pituitary and Neuroendocrine Center, University of Michigan, Ann Arbor, MI, USA.
authors: Stephen E
authors: SE
authors: Sullivan
authors: Division of Metabolism, Endocrinology, and Diabetes, Internal Medicine Department, University of Michigan, 24 Frank Lloyd Wright Drive, G-1500, P.O. Box 482, Ann Arbor, MI, 48106, USA.|Department of Neurosurgery and the Pituitary and Neuroendocrine Center, University of Michigan, Ann Arbor, MI, USA.
authors: William F
authors: WF
authors: Chandler
authors: Division of Metabolism, Endocrinology, and Diabetes, Internal Medicine Department, University of Michigan, 24 Frank Lloyd Wright Drive, G-1500, P.O. Box 482, Ann Arbor, MI, 48106, USA. abarkan@umich.edu.|Department of Neurosurgery and the Pituitary and Neuroendocrine Center, University of Michigan, Ann Arbor, MI, USA. abarkan@umich.edu.
authors: Ariel L
authors: http://orcid.org/0000-0002-5453-0248
authors: AL
authors: Barkan
mesh_terms: D000172:Acromegaly / Q000097:blood* / Q000453:epidemiology / Q000209:etiology; D000236:Adenoma / Q000150:complications / Q000473:pathology; D000328:Adult; D005260:Female; D049912:Growth Hormone-Secreting Pituitary Adenoma / Q000150:complications / Q000473:pathology; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D010902:Pituitary Gland / Q000473:pathology; D015995:Prevalence; D012189:Retrospective Studies
chemical_list: D019382:Human Growth Hormone
keywords: Acromegaly; Growth hormone; Insulin-like growth factor 1; Pituitary tumor