Ciliary neurotrophic factor (CNTF) is a protein encoded by the CNTF gene in humans. Human CNTF is a single-chain polypeptide consisting of 200 amino acid residues, with a molecular weight of 22.7 kDa. The protein acts as a peptide hormone and its effects are limited to promoting neurotransmitter synthesis and axonal growth in certain neuronal populations within the nervous system. CNTF serves as an effective survival factor for neurons and oligodendrocytes and may be involved in reducing tissue damage during inflammatory episodes. It has also been demonstrated that CNTF can be expressed in bone surface cells and can decrease the activity of osteoblasts, contributing to bone metabolism.