Takotsubo Cardiomyopathy in Thyrotoxicosis

I have read with interest the case report of Kwon et al. entitled “A case of Takotsubo cardiomyopathy in a patient with iatrogenic thyrotoxicosis” [1]. I would like to make a few comments regarding the etiology of Takotsubo cardiomyopathy in this case. Takotsubo cardiomyopathy is a type of non-ischemic cardiomyopathy in which there is a sudden temporary weakening of the myocardium and reversible apical ballooning [1]. In the literature there are six more reported cases of Takotsubo cardiomyopathy with thyrotoxicosis so far. When evaluated, five of these cases had Graves' disease [2–6] and one case had Hashimoto thyroiditis [7]. All cases with Graves' disease had positive TSH receptor antibodies [2–6] and except one [3] all of them had overt hyperthyroidism. This case by Bilan et al. had a 5-year history of Graves' disease and had stopped anti-thyroid drug treatment due to euthyroidism several months before developing Takotsubo cardiomyopathy [3]. On admission her TSH value was 0.63 IU/ml and thus she was still euthyroid. The case reported by Sakaki et al. had overt hyperthyroidism on admission, and had positive anti-thyroglobulin (anti-Tg) and anti-thyroid peroxidase (anti-TPO) antibodies [7]. Her TSH receptor antibodies were negative and after a thyrotoxic phase she developed hypothyroidism, which was compatible with Hashimoto thyroiditis [7].