Second, Th1 cytokines (e.g., IFN-γ, TNF-α) mediate thyroid follicular cell apoptosis, triggering transient thyrotoxicosis, followed by Hashimoto-like pathology with elevated thyroid peroxidase antibodies (TPOAb), ultimately progressing to permanent hypothyroidism (29). This evidence concerns the gene IFNG and hypothyroidism.