Tropomyosin receptor kinase A (TrkA), also known as neurotrophic tyrosine kinase receptor type 1 (NTRK1), is a member of the neurotrophic tyrosine kinase receptor (NTKR) family. This kinase is a membrane-bound receptor that, upon neurotrophin binding, phosphorylates itself and members of the MAPK pathway. TrkA mediates the multiple effects of nerve growth factor, which include neuronal differentiation and avoidance of programmed cell death. The presence of TrkA leads to cell differentiation and may play a role in specifying sensory neuron subtypes. Mutations in this gene have been associated with congenital insensitivity to pain with anhidrosis, self-mutilating behavior, mental retardation and cancer. TrkA has a crucial role in the development and function of the nociceptive reception system as well as establishment of thermal regulation via sweating. It also activates ERK1 by either SHC1- or PLC-gamma-1-dependent signaling pathway. Defects in TrkA are a cause of congenital insensitivity to pain with anhidrosis and thyroid papillary carcinoma.