Somatostatin analogues in the treatment of thyroid eye disease

Recent studies have shown successful therapy with the long-acting somatostatin (SM) analogues octreotide and lanreotide in patients with thyroid eye disease (TED). In one such study it was also found that response to low-dose octreotide treatment (300 microg) in these patients was correctly predicted by [111In-DTPA-D-Phe1]-octreotide scintigraphy and concluded that this parameter should be used as a predictive test of the effectiveness of treatment with nonradioactive octreotide. It has also been suggested that octreoscan-111 may be seen as a parameter of disease activity in TED. However, it remains to be clarified whether octreoscan-111 predicts the therapeutic outcome better than the clinical activity score, or magnetic resonance imaging (MRI) or finally measurement of glucosaminoglycan (GAG) in the plasma and/or urine. The exact mechanism of action of SM analogues has not yet been fully clarified. Three explanations may be offered. First, SM suppresses insulin-like growth factor 1 (IGF-1) activity and inhibits IGF-1-mediated effects. A second possible mechanism could be the direct inhibition of the release of cytokines from T-lymphocytes, and finally, SM analogues may act on target cells through specific cell surface receptors. In view of the encouraging therapeutic results reported thus far in several studies, SM analogues may provide a valuable therapeutic alternative to corticosteroids, especially in patients who cannot tolerate the latter. However, further prospective, placebo-controlled studies with a large number of patients are needed before we can reach final conclusions.