 TSH first binds to its receptors which are joined to G proteins, and then induces the activation of the enzyme adenylate cyclase, which will raise the intracellular levels of cAMP.This can activate the CREB transcription factor (cAMP Response Element-Binding) that will bind to the CRE (cAMP Responsive Element).However, this might not occur and, instead, the increase in cAMP can be followed by PKA (Protein kinase A) activation and, as a result, the activation of the transcription factor Pax8 after phosphorylation.