What is the role of somatotropinoma (gigantism) in the pathophysiology of hyperpituitarism?

Updated: Oct 24, 2016
  • Author: Alicia Diaz-Thomas, MD, MPH; Chief Editor: Robert P Hoffman, MD  more...
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Answer

GH-secreting adenomas are rare in childhood. Gigantism refers to GH excess in childhood when open epiphysial plates allow for excessive longitudinal growth. Most cases of gigantism result from GH-secreting pituitary adenomas or hyperplasia. Although gigantism is thought to occur as an isolated disorder, it occasionally represents one feature of other conditions (eg, multiple endocrine neoplasia [MEN] type 1, McCune-Albright syndrome [MAS], neurofibromatosis, tuberous sclerosis, Carney complex).  In both European and Mexican cohorts, mutations in AIP, aryl hydrocarbon receptor-interacting protein, have been associated with early onset gigantism. [1, 2] There are also recent studies describing other genetic underpinnings of childhood growth hormone secreting adenoma.  In two separate series, microduplications in Xp26.3 were found to be an important mutation causing early onset gigantism. [3, 4]    

Mammosomatotrophs are the most common type of GH-secreting cells in childhood gigantism; hence, GH-secreting adenomas often stain for and secrete PRL (67% in one study). GH-secreting tumors in pediatric patients are more likely to be locally invasive or aggressive than those in adult patients. Activating mutations of the stimulatory Gs alpha (Gsa) protein have been identified in the somatotrophs of pituitary lesions in MAS and in as many as 40% of sporadic GH-secreting pituitary adenomas.


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