Endocrine Abstracts

Introduction: Hyperfunctioning thyroid nodules (toxic adenomas) comprise one of the most common causes of hyperthyroidism and are usually treated with therapeutic radioiodine administration (RAI). Coexistence of such nodules with Graves’ disease (GD) is a rare disorder (Marine-Lenhart syndrome) with a reported prevalence of approximately 2.7–4.1% in GD patients. We present a rare variant of this condition, featuring the case of a patient with hyperfunctioning nodular thyroid disease and development of post-RAI endocrine opthalmopathy due to activation of occult autoimmune thyroid component with an excessive elevation of thyroid-stimulating autoantibodies (TRAb).

Case report: A 48-year old smoking female patient with newly detected subclinical hyperthyroidism and related symptoms presented for endocrinological evaluation. She reported no signs/symptoms of orbitopathy. The neck ultrasound revealed 3 heteroechoic nodules of the right thyroid lobe; the adjunctive ^99mTc- scintigraphy was diagnostic for a toxic adenoma and functional suppression of the rest thyroid parenchyma. The patient underwent radioiodine therapy with administration of 12.5 mCi J¹³¹. Iatrogenic hypothyroidism developed 3 months post-therapeutically and was treated with oral administration of levothyroxine over a period of 5 months before cessation of therapy due to tendency of supplementation-induced TSH suppression. The patient presented after 2 months with bilateral eye-lid swelling and redness, as well as lacrimation. An evaluation of TRAb showed high titers of > 40 IU/l (reference range < 1.75 IU/l). The patient was treated with selenium administration over a period of 6 months and reported a progressive remission of her eye symptoms. Due to concomitant relapse of overt hypothyroidism she was started on levothyroxine and remained euthyroid under 62 µg daily.

Conclusion: Radioiodine for the treatment of hyperthyroidism due to nodular thyroid disease may trigger endocrine opthalmopathy in terms of autoimmune activation in patients with undiagnosed occult Graves’ disease, especially in active smokers. Therefore, an estimation of TRAb should be considered in every patient with a diagnosis of toxic adenoma and thyroid scintigraphy non suggestive for concomitant Graves’ disease. In such rare cases, a careful follow-up should be conducted for the early detection of post-RAI orbitopathy and where indicated a prophylactic post-therapeutic corticosteroid coverage should be administered.