How is somatotropinoma treated in hyperpituitarism?

Updated: Oct 24, 2016
  • Author: Alicia Diaz-Thomas, MD, MPH; Chief Editor: Robert P Hoffman, MD  more...
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Somatostatin analogs are highly effective therapies for patients with GH excess. Octreotide suppresses circulating GH levels to less than 2.5 µg/L in 65% of patients with acromegaly and normalizes IGF-I levels in 70% of patients. Long-term studies of patients older than 14 years confirm that the effects of octreotide remain well sustained over time. Octreotide also shrinks tumors, but the effect is generally modest.

A continuous subcutaneous infusion of octreotide in a pubertal boy with pituitary gigantism consistently suppressed GH production. New long-acting formulations, including long-acting octreotide and lanreotide, have been reported to consistently suppress GH and IGF-I in patients with acromegaly with once monthly or biweekly intramuscular depot injections. The author has had success in using the sustained-release formulation in a female adolescent with MAS-related GH excess and can provide details upon inquiry.

Dopamine agonists bind to pituitary dopamine type 2 (D2) receptors and suppress GH secretion, although the precise mechanism of action remains unclear. PRL levels are often adequately suppressed; however, GH levels and IGF-I levels are rarely normalized with this treatment modality. Fewer than 20% of patients achieve GH levels less than 5 ng/mL and fewer than 10% achieve normalization of circulating IGF-I levels. Tumor shrinkage occurs in a minority of patients. A dopamine agonist is generally used as adjuvant medical treatment for GH excess. Its effectiveness may be additive to that of octreotide. Long-acting formulations are available, but data on long-term control of GH and IGF-I with these agents are not available.

A novel hepatic GH receptor antagonist recently has been approved by the Food and Drug Administration (FDA). Pegvisomant (Sensus Corporation, Austin, Tex) effectively suppresses circulating GH and IGF-I levels in patients with acromegaly due to pituitary tumors, as well as ectopic GHRH hypersecretion. IGF-I levels are normalized in as many as 90% of patients treated daily with this drug for 3 months.

Long-term studies are underway. The ACROSTUDY database provides an opportunity to assess the long-term safety of pegvisomant in the treatment of acromegaly. [8] The main safety focus of this long-term follow up is on the potential risk of increased pituitary tumor size, potential for increased liver enzymes, and effects of pegvisomant at the injection site. There are 33 patients in the cohort younger than 18 years. Overall, it seems a selection bias may exist towards more severely affected patients, most subjects were enrolled in Europe, where pegvisomant is registered for patients in whom every other therapeutic intervention failed to control their acromegaly. In the future, additional data on more patients for longer duration will provide further information about the treatment of this rare condition.

Pediatric experience, although scant, has been published and agrees with the efficacy and adverse event profile reported with adult patients.

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