ABSTRACT Introduction Apalutamide (APA) is an androgen receptor signaling inhibitor widely used for metastatic hormone‐sensitive prostate cancer (mHSPC), though it can induce hypothyroidism. We report a severe case of APA‐induced hypothyroidism in a patient with a history of total thyroidectomy. Case Presentation A 65‐year‐old man receiving levothyroxine (175 μg/day) after thyroidectomy was diagnosed with mHSPC (Gleason score 4 + 4; PSA 13 904 ng/mL) with findings suggestive of cancer‐associated disseminated intravascular coagulation. Following APA initiation (240 mg/day), PSA decreased rapidly to 0.01 ng/mL. However, TSH levels rose progressively despite increasing levothyroxine to 275 μg/day. After a 4‐month follow‐up interruption, TSH reached 187.9 mIU/L. APA withdrawal led to rapid TSH improvement. Conclusion Careful TSH monitoring is essential during APA treatment, especially in patients with pre‐existing thyroid dysfunction or prior thyroidectomy. Appropriate levothyroxine titration and multidisciplinary collaboration are essential for the continuation of oncological therapy with APA.
Furumido et al. (Sun,) studied this question.
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