DOI: https://doi.org/10.36347/sjmcr.2026.v14i03.039

Pages: 481-483

Marine-Lenhart syndrome is a rare cause of hyperthyroidism characterized by the coexistence of Graves’ disease and one or more autonomously functioning thyroid nodules, with significant diagnostic and therapeutic implications. We report the case of a 40-year-old man who presented with severe clinical and biochemical hyperthyroidism and positive thyrotropin receptor antibodies consistent with Graves’ disease. Cervical ultrasound identified a left thyroid nodule classified as EU-TIRADS 4. Thyroid scintigraphy, performed after the initiation of antithyroid drug therapy, revealed a hyperfunctioning (“hot”) nodule within a diffusely hyperactive thyroid gland, confirming the diagnosis of Marine-Lenhart syndrome. This scintigraphic pattern established the coexistence of autoimmune hyperthyroidism and nodular autonomy. Given the persistence of hyperthyroidism and the presence of an autonomously functioning nodule, definitive treatment with radioactive iodine therapy was indicated. Marine-Lenhart syndrome should be suspected in patients with Graves’ hyperthyroidism associated with thyroid nodules, particularly when imaging demonstrates focal areas of increased uptake within a diffusely hyperfunctioning gland. Early recognition of this uncommon entity is essential, as it may influence therapeutic strategy and favor definitive treatment approaches to achieve sustained remission and prevent relapse.