Endocrine Abstracts

JOINT2860

The occurrence of Graves’ disease in ectopic thyroid tissue following total thyroidectomy is a rare event, as is the coexistence of Graves’ disease and primary hyperparathyroidism. While both conditions are relatively common in endocrinology practice, their concurrent presentation is unusual, raising the possibility of an association with prior radioiodine (RAI) therapy. RAI-induced hyperparathyroidism has an average latency period of 24 years, with this period decreasing as the patient’s age at the time of RAI treatment increases. This case report describes the rare occurrence of recurrent Graves’ disease in ectopic thyroid tissue, complicated by primary hyperparathyroidism, in a patient with a history of RAI treatment.

Case Report: A 47-year-old woman with a history of Graves’ disease initially presented with an enlarged, nodule-free goiter. Following unsuccessful thionamide treatment, she underwent total thyroidectomy for compressive symptoms and subsequently developed hypothyroidism. Four years later, a progressively enlarging mass appeared in the right anterior neck. Elevated and rising levels of thyroid-stimulating immunoglobulin and thyroid-stimulating hormone receptor antibodies were observed, necessitating levothyroxine dose reduction and eventual cessation due to subclinical hyperthyroidism. Ultrasound revealed a 3 cm, hyperechogenic, hypervascularized nodule in the infrahyoid region. A subsequent scintigraphy confirmed hyperfunctioning ectopic thyroid tissue in this location. Following 10 mCi of I-131 RAI therapy, hyperthyroidism resolved, and cervical ultrasound remained stable for eight years. At that point, an hypoechoic nodular lesion was detected in the right inferior thyroid bed, accompanied by hypercalcemia (11.7 mg/dl), elevated PTH (180 pg/ml), and normal vitamin D levels. Parathyroid scintigraphy confirmed hyperfunctioning parathyroid tissue in the right suprasternal region. The patient underwent right parathyroidectomy, resulting in resolution of hypercalcemia and hyperparathyroidism.

Conclusion: Recurrent Graves’ disease due to hyperfunctioning ectopic thyroid tissue after total thyroidectomy is a rare phenomenon. Remnant or ectopic thyroid tissue can become hyperfunctional in the presence of thyroid-stimulating hormone receptor antibodies, leading to growth and presenting as a mass. This case highlights also the rare coexistence of Graves’ disease and primary hyperparathyroidism, potentially associated with prior RAI treatment. Post-RAI treatment, we recommend periodic serum calcium level monitoring every 3–5 years. This case emphasizes the importance of long-term follow-up and vigilant surveillance for new or emerging endocrine abnormalities, including hyperparathyroidism, even years after initial therapies.