Pazopanib is an oral multi-targeted tyrosine kinase inhibitor and has been approved for metastatic renal cell carcinoma and advanced soft tissue sarcoma. To the best of our knowledge, pazopanib-induced thyrotoxicosis has never been reported. The patient was a 68-year-old woman with renal cell carcinoma and multiple metastases. Three weeks after pazopanib medication, she felt fatigue and palpitation. She was admitted because of liver chemistry abnormalities [AST 723 IU/L (normal range 7-37 IU/L); ALT 953 IU/L (normal range 3-33 IU/L)]. She showed abnormal thyroid function tests with suppressed TSH of 0.0585 μIU/mL, and elevated fT4 of 3.38 ng/dL. Ten days after admission, tachycardia appeared and fT3 and fT4 were elevated (fT3 27.85 pg/mL, fT4 2.58 ng/dL), and TSH was suppressed (0.0414 μIU/mL). Her thyroid ultrasound showed hypervascular thyroid gland without nodules. We diagnosed pazopanib-induced thyrotoxicosis. Because the fT3/fT4 ratio was high (10.8) and the thyroid was enlarged, we thought that her thyrotoxicosis might get worse. She was treated with medication of beta-blockers, hydrocortisone, and potassium iodide and thyrotoxicosis resolved. This report highlights that Pazopanib could induce thyrotoxicosis, and therefore, periodic surveillance of thyroid function is required during pazopanib therapy.

International cancer conference journal. 2017 Mar 27*** epublish ***

Sohei Kuribayashi, Tetsuya Takao, Yohei Okuda, Masataka Kawamura, Kosuke Nakano, Nozomu Kishimoto, Kentaro Takezawa, Go Tanigawa, Koichi Tsutahara, Hirotaka Watanabe, Yutaka Umayahara, Seiji Yamaguchi

Department of Urology, Osaka General Medical Center, 3-1-56 Bandai Higashi, Sumiyoshi-ku, Osaka, 558-8558 Japan., 2Department of Diabetes and Metabolism, Japan Community Health Care Organization Osaka Hospital, Osaka, Japan., Department of Diabetes and Metabolism, Osaka General Medical Center, Osaka, Japan.