Rare Presentation of Marine-Lenhart Syndrome

The combination of autoimmune Graves’ disease with a solitary hot thyroid nodule suppressing the remainder of the thyroid gland is rare. We report a case of Graves’ disease associated with a single hyperfunctioning nodule with suppression of the remaining gland. A 45 year old male patient with past medical history of autoimmune Graves’ disease with severe ophthalmopathy was referred to endocrine clinic. His symptoms started with dry eyes several years ago without associated hypermetabolic symptoms. Further investigation revealed hyperthyroidism; he was started on methimazole. Thyroid stimulating immunoglobulin was 484 %( reference: <140%, Method: immunoassay). Thyroid scan with I-123 sodium iodide showed uptake of 28.3 percent at 24 hours, and showed a large area of intense activity mid and lower left thyroid lobe with suppression of uptake in the rest of the thyroid gland. Thyroid ultrasound showed a heterogeneous well-defined 1.3x1.0x1.0 cm left mid lower pole nodule. These findings are suggestive of a rare variant of Marine-Lenhart syndrome. Graves’ hyperthyroidism is thought to be caused by autoantibodies stimulating the TSH receptors. Thyroid nodules associated with Graves’ disease have been reported with the incidence between 25 to 30%, most of which are cold nodules. The incidence of Graves’ disease accompanied by hot nodules ranges from 2.7 to 4.1%.These rare cases of Graves’ disease with accompanying functioning thyroid nodules are known as Marine-Lenhart syndrome. Most reported cases of Marine-Lenhart syndrome are Graves’ disease with multiple hyperfunctioning nodules. Our case represents an unusual variety in which Graves’ disease with a hyperfunctioning solitary nodule was associated with suppression of the remaining gland. Acquired mutations resulting in constitutively activated TSH receptors and the presence of anti TSH receptor autoantibodies might be responsible for the development of Marine-Lenhart syndrome.