A case presenting with thyrotoxicosis, which is thought to be related to radiation-induced thyroiditis

Abstract

Abstract Background: Thyrotoxicosis is characterized by diverse symptoms, various etiological causes, and a number of different treatment options. Rational and appropriate treatment requires an accurate diagnosis. A well-made differential diagnosis and consideration of concomitant medical conditions are essential for an accurate diagnosis. We present a detailed differential diagnosis of an instructive case with thyrotoxicosis onset which might be associated with more than one etiological factor.Case Report: A 45-year-old woman who received chemoradiotherapy for a known laryngeal tumor was admitted with complaints of palpitation, tremor, sweating, and amenorrhea. She had also been using lithium for nearly two years with a diagnosis of bipolar disorder. On examination, she was pale, with tremors, and sweaty. Her heartbeat was 124 beats/min. The thyroid was nonpalpable. TSH was suppressed, free T3 and free T4 were high. TSHR-Ab and autoantibodies were not detected. Acute phase reactants were found to be normal. Bilateral thyroid lobes and size of isthmus were normal in thyroid ultrasonography. The technetium uptake level was determined as 0%. In the etiology, it was thought that the case of thyrotoxicosis, which developed based on radiotherapy-induced thyroiditis, developed hypothyroidism over time due to permanent damage to the thyroid follicles. L-thyroxine was started in the hypothyroid phase, euthyroid was provided with 75 µg and she was followed up.Conclusion: For a rational treatment and follow-up, the etiology must be determined precisely. For this, a detailed anamnesis, a comprehensive physical examination, and rational, cost-effective, and good laboratory practices are required. It should be kept in mind that thyrotoxicosis may pass into the hypothyroid phase in the follow-up. The fact that each step contains clinical lessons and that it is an educational and instructive case necessitated presenting it.