What is the role of pharmacologic therapy in the treatment of gigantism and acromegaly in McCune-Albright syndrome (MAS)?

Updated: Jan 17, 2019
  • Author: Gabriel I Uwaifo, MD; Chief Editor: George T Griffing, MD  more...
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Answer

Management of GH excess in the setting of MAS should be achieved by using pharmacotherapeutic agents because such excess is invariably the result of diffuse nodular pituitary hyperplasia rather than of a single definitive adenoma. Surgical removal of adenomas, even if they appear to be present on radiologic testing, may be complicated by coexisting fibrous dysplasia (FD) involving the skull bones that distorts anatomic planes and increases the potential for torrential intraoperative bleeding.

Irradiation of the pituitary is also not ideal, given the potential risk of inducing sarcomatous degeneration in bones affected by FD. No systemic investigation into the use of focused gamma knife–based pituitary irradiation has been done, because this condition is so uncommon.

Most patients with GH excess in MAS are treated with octreotide in dosages similar to those used in regular acromegaly, beginning at 50 µg subcutaneously (SC) every 8 hours and then titrated to response (on the basis of insulinlike growth factor 1 [IGF-1] and postinjection GH levels) to levels as high as 1500 µg/day. Octreotide successfully lowers GH levels in many cases but rarely normalizes GH secretion. Long-acting somatostatin analogues (eg, depot octreotide and lanreotide) have also been used on a case-by-case basis. [60]

The dopamine agonists bromocriptine and cabergoline have also been used to decrease GH secretion. (A third dopamine agonist, pergolide, was withdrawn from the US market in March 2007.) These agents appear to have particular utility in the setting of prolactin and growth hormone co-hypersecretory states suggestive of somatomammotropinomas.

Dopamine agonists have been used as monotherapy but are typically used in conjunction with octreotide. A study showed that cabergoline was able to decrease GH secretion but was unsuccessful in bringing GH secretion down to normal. Combined octreotide-cabergoline therapy has yielded additional improvement in GH secretion in comparison with monotherapy, but in general, it has not been successful in bringing levels down to normal.

No systemic data are presently available on the utility or place of GH receptor antagonists (eg, pegvisomant [61] ) in managing MAS-associated GH excess. Such therapy is not contraindicated; however, the inability of these agents to control GH levels would probably make their use as monotherapy in this setting inadvisable.


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