The role of somatostatin agonistic analogs in the treatment of acromegaly

Abstract

Acromegaly mainly associated with the presence of a growth hormone (GH)-secreting pituitary tumor causes considerable morbidity and carries a risk of premature mortality. Treatment includes surgery, radiotherapy, and the use of dopaminomimetic drugs and somatostatin agonist analogs (octreotide and lanreotide). The use of long-acting somatostatin analogs is limited to adjuvant therapy following failure of surgery and/or radiotherapy and/or bromocriptine. But it may be considered the drug of choice for childhood acromegaly and for syndrome of plurihormonal pituitary overproduction in association with excess GH-releasing hormone (GHRH) and a McCune/Albright-like syndrome. Octreotide has been administered de novo as primary and/or presurgical preparatory therapy. Octreotide doses of 100 to 1500 micrograms were used in two large series in Europe and the United States, which mainly included acromegalics in whom all other modalities had failed (> 65%). Clinical improvement, which was sustained for over 6 months of follow-up evaluation, was reported for more than 50% to 70% of patients. In evaluable patients with visual-field defects, there was a definite amelioration, even if the tumor mass was not reduced, and there was no worsening during therapy; the same is true for the adenoma mass, which showed a variable reduction (median, 15 to 22%). A reduction of serum GH and insulin-like growth factor-1 (IGF-1) levels was found in more than 90% of patients, with GH serum values < 5 ng/mL and IGF-1 serum values < 2 U/mL recorded in 46% and 49%, respectively. Relapse occurred when treatment stopped. Future developments are expected to improve the clinical usefulness of somatostatin analogs.