Objective : Graves’ disease (GD) associated with a solitary hot thyroid nodule suppressing the remainder of thyroid gland is rare and was initially described in 1911 by Marine and Lenhart. We report a case of GD associated with a single hyperfunctioning right thyroid nodule with suppression of rest of the thyroid.
Methods : N/A
A 67 year old female was referred for evaluation for abnormal thyroid function test. Patient was having hair loss, palpitations and fatigue but denied any difficulty swallowing, change in voice, bowel habits, weight loss, radiation to neck, new medications or family history of thyroid disease. Laboratory test showed low TSH <0.01 (0.4-4.5 mIU/L), elevated free T3 5.9 (2.3-4.2 pg/mL), normal total T4 10.3 (4.5-12 mcg/dL) with elevated thyroid stimulating immunoglobulin (TSI) at 396 (<140%).Thyroid ultrasound showed a right thyroid lobe nodule measuring 1.4 x 1.3 x 1.4 cm. Radioiodine Thyroid uptake scan showed increased uptake of 74% with suppression of the left thyroid lobe.
FNAB of right thyroid nodule showed benign follicular cells. Repeat TSH was undetectable with free T4 of 1.8 (0.8-1.8 ng/dL) and TSI still high (582). She was started on methimazole 10 mg daily. After starting methimazole, repeat labs showed free T4 1.1, TSH 0.08 and total T3 81 (76-181 ng/dL) improved. She had resolution of her symptoms. Over the time, TSH became undetectable, free T4 was normal and total T3 mildly increased 157. We increased methimazole to 20 mg daily. Three months later, she was clinically and biochemically euthyroid (TSH 3.83, free T4 0.8 and total T3 86) and was continued on methimazole 20 mg/day.
Discussion : Thyroid nodules are found in 25-30% of patients affected by GD but >95% of those are hypofunctioning. Hyperfunctioning thyroid nodule with GD, called Marine-Lenhart (ML) syndrome, is very rare and challenging disease to diagnose and manage. Our patient had complete suppression of left thyroid lobe from hyperfunctioning right lobe nodule in the background of elevated TSI. Thyrotoxicosis in ML syndrome can be due to Graves’ disease or the nodule which may be hyperfunctioning at the beginning or may turn autonomous later in the course. It is very easy to miss the diagnosis of GD in these patients unless antibodies are checked. It is important to recognize this entity as these patients are at risk of developing other features of Graves’s disease like Graves’s ophthalmopathy and dermatopathy. The nodule may need radioiodine ablation if patient does not respond to methimazole.
Conclusion : Our patient had typical features of Marine-Lenhart syndrome and responded well to methimazole. However, it is very important to be vigilant about such rare diagnosis.
University at Buffalo, SUNY
I am a second year Endocrinology fellow at University at Buffalo, SUNY.