Abstract
BACKGROUND: Hyperthyroidism, caused by metastatic differentiated thyroid cancer, is a rare condition that can be difficult to diagnose. Thyrotoxicosis and metastatic disease regarding functional metastasis increase morbidity and mortality in patients with functional metastasis and need to be treated. This study aims to present a case of hyper-functional metastasis of thyroid cancer to analyze its pathological features, diagnostic procedures, and treatment options and to gather and examine recent cases of hyper-functional metastasis of thyroid cancer. CASE PRESENTATION: A 26-year-old Iranian woman presenting with hyperthyroidism and a solid cystic nodule measuring 14.5 × 15.7 × 19.6 mm in the left thyroid lobe underwent thyroid surgery revealing papillary thyroid carcinoma. Despite lymph node metastasis, she refused further surgery and opted for lymph node radiofrequency ablation and radioactive iodine therapy. Subsequent follow-ups showed no recurrence of lymphadenopathy, normalized thyroid function, and decreasing triglyceride levels, with the patient under surveillance. CONCLUSION: Radioactive iodine is a first-line treatment option for patients with hyperactive thyroid cancer presenting with metastatic disease. Another therapeutic option is surgery, which is performed to maximize the reduction of thyroid tissue, lymph nodes, and distant metastasis.