Somatostatin Receptor Scintigraphy Before and After Treatment with Somatostatin Analogues in Patients with Thyroid Eye Disease

Abstract

Octreotide, a potent synthetic long-acting somatostatin analogue, has been shown to have a beneficial effect in thyroid eye disease (TED). Orbital scintigraphy using ocetreoscan-111 is a useful study, which can be used to visualize somatostatin-receptor-bearing cells and also to select patients who might benefit from octreotide therapy. One major limitation of this therapy is that the drug must be administered parenterally and used several times daily. Lanreotide, a new somatostatin analogue, has a much longer duration of action in comparison with octreotide, and has recently been found to have a beneficial effect in the treatment of thyroid eye disease. The aim of this study was to investigate the orbital Indium-111-pentetreotide activity after treatment with octreotide and lanreotide in patients with thyroid ophthalmopathy. Fourteen patients were studied. 12 with bilateral and 2 with unilateral thyroid eye disease, (10 females and 4 males) and all with moderately severe symptoms of ophthalmopathy. All were treated with antithyroid drugs and were euthyroid at the time of the study. All patients were investigated with orbital scintigraphy using octreoscan-111 and selected for study on the basis of a positive octreoscan. Five patients received 30 mg lanreotide intramuscularly once every 2 weeks over a period of 3 months, and 5 patients received octreotide 100 μg subcutaneously thrice daily for 3 months. Four patients served as controls and received no treatment. The octreoscan-111 scintigraphy was repeated in all patients 3 months after the first examination. The NOSPECS classification and the clinical activity score (CAS) of thyroid ophthalmopathy were also evaluated before and 3 months after the initiation of treatment. All patients who received treatment had a negative follow-up octreoscan while controls had a positive octreoscan. NOSPECS score and CAS were improved with treatment, but unchanged in control patients. The reduced uptake of octreoscan may be the result of blocking of somatostatin receptors, or reduction in receptor-expressing tissues, downregulation of somatostatin receptors in target tissues, or a combination of these factors.