CASE REPORT
A sixty-nine-year-old male started hemodialysis in 2017 due to diabetic kidney disease. Roxadustat (a HIF-PH inhibitor) was started at a dose of 100mg for recombinant human EPO-resistant anemia in August 2020. The dose of roxadustat was increased to 200 mg to improve his anemia. TSH and fT4 were within the normal range during recombinant human EPO administration. General malaise gradually developed after starting roxadustat. His TSH and fT4 gradually decreased to 0.47μIU/mL and 0.15 ng/dL, respectively. Furthermore, cholesterol levels were markedly low (Total-C 84 mg/dL, HDL-C 48 mg/dL, LDL-C 31 mg/dL). Levothyroxine (a synthetic thyroxine) was started at a dose of 12.5 μg for hypothyroidism in February 2021 and was admitted to the hospital for further examination. Oral medications at an administration were levothyroxine, antihypertensive drugs, and antiplatelet drugs. There was no fever or hypothermia, blood pressure was 160/84 mmHg, and pulse rate was 78 beats/minus. There were no abnormal physical findings, including thyroid.
Laboratory data is shown in Table 1. Thyroid-related auto-antibodies were negative. No abnormalities were observed in other pituitary hormones. Brain MRI revealed no abnormality in the pituitary gland. A TRH stress test was performed and the patient was diagnosed with central hypothyroidism (Table 2).
The dose of levothyroxine was increased for central hypothyroidism. After administration of 200 μg of levothyroxine, fT4 recovered quickly into the normal range, but TSH did not recover. Central hypothyroidism might be speculated as an adverse effect of roxadustat. In January 2021, roxadustat was switched to daprodustat (Fig.1). After discontinuing roxadustat, TSH recovered rapidly into the normal range. Moreover, cholesterol levels increased. TRH test was performed again, and the results were normal. Therefore, central hypothyroidism was reversible. Levothyroxine was tapered and discontinued, but thyroid function remained within the normal range.