IRS1 and Insulin resistance: The TSH binds to TSHR on the surface of adipocytes, then activates cyclic adenosine monophosphate-protein kinase A (cAMP-PKA) pathway, activates tumor necrosis factor-α (TNF-α) gene transcription and secretion of TNF-α, and further downregulates the expression of insulin receptor substrate-1 (IRS-1), which plays a role in insulin resistance.