A case of thyrotoxicosis-induced anemia in a patient with painless thyroiditis

There have been several reports of secondary anemia associated with Graves' disease. There are no reports of secondary anemia resulting from thyrotoxicosis due to painless thyroiditis (silent thyroiditis). We report the case of a patient with pancreatic diabetes who developed anemia caused by thyrotoxicosis due to painless thyroiditis.

The patient was a 37-year-old man who visited the hospital complaining of fatigue, palpitations, and dyspnea. His hemoglobin was 110 g/l (reference range, 135-176), and mean corpuscular volume was 81.5 fl (81.7-101.6). His free thyroxine (FT4) was high, at 100.4 pmol/l (11.6-21.9); the free triiodothyronine (FT3) was high, at 27.49 pmol/l (3.53-6.14); TSH was low, at < 0.01 mIU/l (0.50-5.00); and TSH receptor antibody was negative. Soluble IL-2 receptor (sIL-2R) was high, at 1340 U/ml (122-496); C-reactive protein (CRP) was high, at 6900 μg/l (< 3000); and reticulocytes was high, at 108 10⁹ /l (30-100). Serum iron (Fe) was 9.5 (9.1-35.5), ferritin was 389 μg/l (13-401), haptoglobin was 0.66 g/l (0.19-1.70. Propranolol was prescribed and followed up. Anemia completely disappeared by 12 weeks after disease onset. Thyroid hormones and sIL-2R had normalized by 16 weeks after onset. He developed mild hypothyroidism and was treated with L-thyroxine at 24 weeks.

This is the first case report of transient secondary anemia associated with thyrotoxicosis due to painless thyroiditis. The change in sIL-2R was also observed during the clinical course of thyrotoxicosis and anemia, suggesting the immune processes in thyroid gland and bone marrow.