Peptide hormone

Preprohormones, peptide hormone precursors, are then processed in several stages, typically in the endoplasmic reticulum, including removal of the N-terminal signal sequence and sometimes glycosylation, resulting in prohormones.

The prohormones are then packaged into membrane-bound secretory vesicles, which can be secreted from the cell by exocytosis in response to specific stimuli (e.g. an increase in Ca2+ and cAMP concentration in cytoplasm).

Specific endopeptidases in the cell cleave the prohormone just before it is released into the bloodstream, generating the mature hormone form of the molecule.

When a peptide hormone binds to a receptor on the surface of the cell, a second messenger appears in the cytoplasm, which triggers signal transduction leading to the cellular responses.

[3] Some peptides (angiotensin II, basic fibroblast growth factor-2, parathyroid hormone-related protein) also interact with intracellular receptors located in the cytoplasm or nucleus by an intracrine mechanism.