However, the gram-negative bacteria Prevotella can induce the transformation of Type 1 T helper cells (Th1) to Type 2 T helper cells (Th2) through lipopolysaccharide (LPS) on their outer membrane to activate the intestinal immune inflammatory system and then destroy the intestinal barrier to cause a “leaky gut” (34, 35), triggering a congenital autoimmune response against thyroid cells (36), which may lead to a reduction in serum thyroid hormone levels and increase TSH levels by negative feedback mechanisms, thereby leading to hypothyroidism. This evidence concerns the gene TG and hypothyroidism.