Peptide Hormone & Neuropeptides

Hormones mediate changes in target cells by binding to specific hormone receptors. Peptide hormones are small, processed, and secreted peptides or protein that signal via membrane receptors and play critical roles in normal and pathological physiology. Peptide hormones are short peptides (<100 amino acids) produced by the proteolytic cleavage of pre-pro-hormone precursors. Mature peptides pass through the secretory pathway and are released into the extracellular space, where they can bind to specific cell surface receptors and modulate cellular functions. Most peptide hormones modulate intracellular signaling pathways and regulate cellular homeostasis by binding to G-protein-coupled receptors (GPCR).
Neuropeptides are diverse neuron-secreted peptides with neuromodulatory, neurotransmitter, or hormonal functions. Most neuropeptides signal via G protein-coupled receptors (GPCRs), with a few exceptions. Neuropeptides play a variety of roles in many physiological processes and serve as potential therapeutic targets for the treatment of some nervous-system disorders.
Both neuropeptide and peptide hormones are synthesized, modified, and degraded by the same sets of enzymes. Furthermore, both can act nearby as autocrine and paracrine agents and at a distance as endocrine agents. The only distinction between neuropeptides and peptide hormones is that a neuropeptide is synthesized and used by a neuron. Indeed, nearly all neuropeptides are also found as peptide hormones and vice/versa. It is important to keep in mind that neuropeptides are not just in the nervous system – they act both in and out of the CNS.