Abstract
Disclosure: R. Alshantti: None. A.M. San Hernandez: None. J. Wu: None. C.P. Barsano: None. M.F. Siddiqui: None. Introduction: Marine-Lenhart Syndrome is a rare condition with a prevalence of 0.8-4.1% of cases with Graves’ disease. It is defined by the coexistence of Graves’ disease and autonomously functioning thyroid nodule(s). It is an under-recognized cause of hyperthyroidism. A limited number of cases have been reported in the literature. We report an interesting case of Marine-Lenhart Syndrome characterized by the presence of elevated thyroid stimulating immunoglobulins (TSI) and an autonomous right thyroid nodule. Case Description: A 37-year-old man with a history of hyperthyroidism from Graves’ disease and a right thyroid nodule was referred to endocrinology clinic. He was diagnosed with hyperthyroidism in 2015 at an outside facility. He had elevated thyroid stimulating immunoglobulins (TSI) and a 2.9 cm right thyroid nodule which was biopsied and had benign cytopathology. Hyperthyroidism was treated with methimazole (MMI) but without subsequent remission of Graves’ disease. He ran out of MMI and re-presented with symptomatic hyperthyroidism with fatigue, tremors, and hyperdefecation. There was no ocular involvement or thyroid compressive symptoms. Biochemical work up was consistent with uncontrolled hyperthyroidism (suppressed TSH 0.01 uIU/mL [Ref range: 0.45-5.33], and elevated FT4 2.58 ng/dl [Ref range: 0.70-2.20], elevated free T3 8.7 pg/ml [Ref range: 2.5-3.9], and mildly elevated TSI 0.72 IU/L [Ref range: 0.54 or less]. MMI was therefore reinitiated. Thyroid Uptake scan demonstrated an increased focal 24-hour Iodine-131 uptake of 57% in the right lobe with suppression of the left lobe. Thyroid ultrasound support the finding of large right thyroid nodule (2.3 x 2.4 x 3.9 cm) with diffuse heterogeneous thyroid. The presence of TSI, lack of control of hyperthyroidism for more than 2 years of treatment, and presence of a functioning thyroid nodule raise the suspicion of Marine-Lenhart Syndrome. Indeed, the findings of an autonomously functioning right thyroid nodule with concomitant Graves’ disease establish the diagnosis of Marine-Lenhart Syndrome. The option of RAI ablation vs total thyroidectomy was discussed with the patient. The patient opted for thyroidectomy. Conclusion: Based on studies, approximately 35% of patients with Graves’ disease have thyroid nodule(s) and only 2.7% are functioning adenomas. The combination of positive TSI or TrAb and functioning thyroid nodules has been termed Marine-Lenhart syndrome. The syndrome was named after David Marine and Carl Lenhart who initially described it in 1911. Unlike Graves’ disease, patients with Marine-Lenhart Syndrome have a lower remission rate with thioamides, require definitive treatment with RAI ablation at a high dose or total thyroidectomy, and may easily be misdiagnosed by many endocrinologists. Presentation: 6/2/2024