Octreoscan in Graves' ophthalmopathy

Viral conjunctivitis interfering with the clinical activity score and management of thyroid ophthalmopathy

INTRODUCTION

The management of Graves' ophthalmopathy is shared between endocrinologists and ophthalmologists. Assessment and treatment of the active inflammatory stage is based on the clinical activity and disease severity scores, often without detailed eye examination by the treating endocrinologist.

MATERIALS AND METHODS

We report a case of acute viral keratoconjunctivitis occurring during immunosuppressive treatment for Graves' ophthalmopathy which masked the signs, symptoms and response to treatment of the orbitopathy, posing a differential diagnostic challenge.

RESULTS

The apparent worsening of the ophthalmopathy and the increased clinical activity score led the treating endocrinologist to alter the management decisions. Ophthalmic examination confirmed the diagnosis of viral keratoconjunctivitis and immunosuppressive treatment was continued with significant final improvement of Graves' ophthalmopathy.

DISCUSSION

Ocular surface conditions, unrecognised by the treating physician, may complicate the assessment of thyroid ophthalmopathy when detailed eye examination is not performed. The diagnostic challenge of Graves' ophthalmopathy requires a combined approach by an endocrinologist and an ophthalmologist working as a team.

Octreoscan in thyroid-associated ophthalmopathy

Until recently, there was no imaging technique available that could be considered as a reliable measure of inflammation in thyroid-associated opthalmopathy (TAO). Pentetreotide (a synthetic derivative of somatostatin) labeled with 111In has been used to visualize somatostatin receptors in endocrine-related tumours in vivo. It has also been used to measure the orbital uptake in patients with TAO. An increased uptake in the orbit was found in patients with active disease. It was suggested that it is caused by the expression of somatostatin receptors on activated T-lymphocytes. Thus, a positive orbital octreoscan indicates clinically active eye disease in which immunosuppressive treatment might be of therapeutic benefit, in contrast to the fibrotic end stage. Indeed, successful immunosuppression with prednisone, orbital irradiation, or very recently with somatostatin analogues, has been demonstrated in patients with TAO and positive octreoscan. It is inferred that an orbital octreoscan is mainly indicated to select patients with TAO who will benefit from immunosuppression. However, limitations such as cost, nonnegligible radiation burden, nonspecific examination for TAO, and finally, lack of evaluation of eye muscle swelling restrict the widespread use of this technique. It remains to be seen if orbital octreoscan will become a widely available tool in the management of patients with TAO.

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.