Somatostatin analogs: a new tool for the management of Graves' ophthalmopathy.

Abstract

Somatostatin (SM), a peptide inhibiting the release of GH, is present and plays an inhibitory role in the regulation of several organ systems in men and other species. Various SM analogs (SM-As) have been developed and used in clinical practice because the short half-life of SM makes it unsuitable for routine treatment. Recently it has been shown that SM-As might be of therapeutic value in the treatment of active thyroid ophthalmopathy. So far, 61 patients have been treated with octreotide and the results have been published in the literature. It was found that in 41 patients the drug had a beneficial effect. Ten patients were given lanreotide and 8 of those had a positive response, while 23 patients were treated with long-acting release octreotide and 16 improved. The exact mechanism of action of SM-As has not yet been fully clarified. One possible mechanism could be a direct inhibition of insulin-like growth factor (IGF)-I mediated effects. A second mechanism could be an inhibition of the release of lymphokines and inflammatory mediators from T-lympocytes. Finally, SM-As may act directly on target cells through specific cell surface receptors. With the introduction from Novartis of SOM-230, a compound which binds with high affinity to SM-receptors (SM-Rs) subtypes 1, 2, 3 and 5, with lower affinity to SM-Rs 4, and which has a very favorable T1/2 of nearly 24 h, a much better therapeutic outcome is expected. Thus, SM-As may provide a well-tolerated therapeutic alternative to corticosteroids. However, prospective placebo-controlled studies with large numbers of patients are needed before their role in the treatment of Graves' opthalmopathy is definitely established.