A different cause is a hyper functioning thyroid adenoma where the follicular cells start growing uncontrollably, forming a benign tumor that makes excess thyroid hormones.

另一个原因是功能亢进的甲状腺腺瘤，即滤泡细胞的生长开始不受控制，形成一个产生过量甲状腺激素的良性肿瘤。