Peptide hormone

A peptide hormone is a signaling molecule made of amino acids. It generally dissolves in water and acts by binding receptors on cell surfaces.

Peptide hormone synthesis: The cellular production and processing of peptide hormones from precursor proteins. Preprohormones are processed through this pathway before becoming active signals.
Amino acid: An organic molecule that serves as a building block of proteins and peptides. Peptide hormones are chains assembled from these molecular units.
Insulin: A peptide hormone produced by pancreatic beta cells that lowers blood glucose by promoting its uptake and storage. It is a major metabolic peptide hormone and a classic example of receptor-mediated signaling.
Steroid hormone: A hormone derived from cholesterol that can cross cell membranes and commonly binds intracellular receptors. Its lipid solubility and typical receptor location contrast with peptide hormones.
Regulated exocytosis: The stimulus-triggered release of molecules when secretory vesicles fuse with a cell membrane. Many peptide hormones leave endocrine cells in response to a specific stimulus.
Peptide: A short chain of amino acids joined by peptide bonds. The hormone's defining molecular structure is a peptide chain.
Glucagon: A peptide hormone from pancreatic alpha cells that raises blood glucose, especially by stimulating liver glucose output. It counterbalances insulin in the regulation of blood glucose.
Thyroid hormone: A hormone derived from tyrosine that regulates metabolism and generally acts through nuclear receptors. Despite its amino-acid origin, it behaves more like a lipid-soluble hormone.
G protein-coupled receptor: A membrane receptor that activates intracellular G proteins when it binds a signal. Many peptide hormones signal through these receptors at the cell surface.
Protein: A biological molecule composed of one or more folded chains of amino acids. Larger peptide hormones and their precursors can be protein-sized.

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