Peptide Hormone

A Peptide Hormone is a polypeptide that is a hormone consisting of amino acid chains that regulate physiological processes through receptor-mediated signaling.

• AKA: Protein Hormone, Polypeptide Hormone, Peptidergic Hormone.
• Context:
  • It can typically contain Amino Acid Sequences ranging from 3 to 200+ amino acids.
  • It can typically be synthesized in Endoplasmic Reticulum through ribosomal translation.
  • It can typically undergo Posttranslational Modification including proteolytic cleavage and glycosylation.
  • It can typically be stored in Secretory Vesicles within endocrine cells.
  • It can typically be released through Exocytosis in response to cellular stimuli.
  • It can typically bind to Cell Surface Receptors on target cells.
  • It can typically activate Second Messenger Systems including cAMP pathways and calcium signaling.
  • It can typically have Water Solubility enabling bloodstream transport.
  • It can typically be degraded by Peptidase Enzymes in circulation and target tissues.
  • It can typically regulate Metabolic Processes through enzyme activation.
  • ...
  • It can often be synthesized as Preprohormones requiring signal peptide removal.
  • It can often be processed into Prohormones before final activation.
  • It can often contain Disulfide Bonds for structural stability.
  • It can often undergo Tissue-Specific Processing yielding different active forms.
  • It can often be subject to Feedback Regulation through endocrine axises.
  • It can often have Short Half-Life requiring pulsatile secretion.
  • It can often interact with Binding Proteins affecting bioavailability.
  • It can often exhibit Species Variation in amino acid sequence.
  • ...
  • It can range from being a Small Peptide Hormone to being a Large Peptide Hormone, depending on its amino acid count.
  • It can range from being a Rapidly-Acting Peptide Hormone to being a Slowly-Acting Peptide Hormone, depending on its onset time.
  • It can range from being a Local-Acting Peptide Hormone to being a Systemic-Acting Peptide Hormone, depending on its action scope.
  • It can range from being a Single-Chain Peptide Hormone to being a Multi-Chain Peptide Hormone, depending on its structural complexity.
  • ...
  • It can be produced by Anterior Pituitary Gland, posterior pituitary gland, hypothalamus, pancreas, thyroid gland, parathyroid gland, gastrointestinal tract, adipose tissue, heart, kidney, or placenta.
  • It can utilize G-Protein Coupled Receptors, receptor tyrosine kinases, or cytokine receptors.
  • It can be classified as Neurohormones when released by neurosecretory cells.
  • It can function as Growth Factors promoting cell proliferation.
  • It can serve as Neuropeptides in neural signaling.
  • ...
• Example(s):
  • Pancreatic Peptide Hormones, such as:
    • Insulin, regulating glucose metabolism through insulin receptor activation.
    • Glucagon, increasing blood glucose levels through hepatic gluconeogenesis.
    • Somatostatin, inhibiting hormone secretion through paracrine action.
    • Pancreatic Polypeptide, regulating pancreatic secretion and gastrointestinal motility.
    • Amylin, co-secreted with insulin for glucose homeostasis.
  • Pituitary Peptide Hormones, such as:
    • Anterior Pituitary Hormones, such as:
      • Growth Hormone (GH), promoting somatic growth and metabolism.
      • Adrenocorticotropic Hormone (ACTH), stimulating cortisol production.
      • Thyroid-Stimulating Hormone (TSH), regulating thyroid function.
      • Follicle-Stimulating Hormone (FSH), controlling reproductive function.
      • Luteinizing Hormone (LH), triggering ovulation and testosterone production.
      • Prolactin, stimulating milk production.
    • Posterior Pituitary Hormones, such as:
      • Oxytocin, promoting uterine contractions and social bonding.
      • Vasopressin (ADH), regulating water balance and blood pressure.
  • Gastrointestinal Peptide Hormones, such as:
    • Incretin Hormones, such as:
      • Glucagon-Like Peptide-1 (GLP-1), enhancing insulin secretion postprandially.
      • Glucose-Dependent Insulinotropic Polypeptide (GIP), stimulating insulin release.
    • Gastrin, stimulating gastric acid secretion.
    • Cholecystokinin (CCK), promoting gallbladder contraction and satiety.
    • Secretin, regulating pancreatic bicarbonate secretion.
    • Ghrelin, stimulating appetite and growth hormone release.
    • Motilin, regulating gastrointestinal motility.
  • Hypothalamic Peptide Hormones, such as:
    • Releasing Hormones, such as:
      • Growth Hormone-Releasing Hormone (GHRH), stimulating GH secretion.
      • Corticotropin-Releasing Hormone (CRH), triggering ACTH release.
      • Thyrotropin-Releasing Hormone (TRH), promoting TSH secretion.
      • Gonadotropin-Releasing Hormone (GnRH), controlling reproductive hormones.
    • Inhibiting Hormones, such as:
      • Somatostatin (GHIH), inhibiting growth hormone release.
      • Dopamine, suppressing prolactin secretion.
  • Tissue-Specific Peptide Hormones, such as:
    • Leptin, from adipose tissue regulating energy balance.
    • Atrial Natriuretic Peptide (ANP), from heart controlling blood pressure.
    • Erythropoietin (EPO), from kidney stimulating red blood cell production.
    • Calcitonin, from thyroid regulating calcium homeostasis.
    • Parathyroid Hormone (PTH), from parathyroid glands controlling calcium levels.
  • ...
• Counter-Example(s):
  • Steroid Hormone, which are lipid-based hormones that pass through cell membranes and bind to intracellular receptors.
  • Thyroid Hormone, which are amino acid-derived hormones but not peptides, acting through nuclear receptors.
  • Catecholamine, which are monoamine hormones derived from single amino acids rather than peptide chains.
  • Eicosanoid, which are lipid hormones derived from fatty acids with local action.
  • Neurotransmitter, which typically act across synaptic clefts rather than through endocrine system.
• See: Hormone, Endocrine System, Peptide, Protein, Signal Transduction, Second Messenger System, G-Protein Coupled Receptor, Exocytosis, Proteolytic Processing, Glycosylation, Disulfide Bond, Prohormone, Endocrine Gland, Autocrine Signaling, Paracrine Signaling, Intracrine Signaling.

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References

2022

• (Wikipedia, 2022) ⇒ https://en.wikipedia.org/wiki/peptide_hormone Retrieved:2022-6-5.
  • Peptide hormones or protein hormones are hormones whose molecules are peptides or proteins, respectively. The latter have longer amino acid chain lengths than the former. These hormones have an effect on the endocrine system of animals, including humans. Most hormones can be classified as either amino acid–based hormones (amine, peptide, or protein) or steroid hormones. The former are water-soluble and act on the surface of target cells via second messengers; the latter, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei. Like all peptides and proteins, peptide hormones and protein hormones are synthesized in cells from amino acids according to mRNA transcripts, which are synthesized from DNA templates inside the cell nucleus. 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). These prohormones often contain superfluous amino acid residues that were needed to direct folding of the hormone molecule into its active configuration but have no function once the hormone folds. Specific endopeptidases in the cell cleave the prohormone just before it is released into the bloodstream, generating the mature hormone form of the molecule. Mature peptide hormones then travel through the blood to all of the cells of the body, where they interact with specific receptors on the surfaces of their target cells. Some neurotransmitters are secreted and released in a similar fashion to peptide hormones, and some “neuropeptides” may be used as neurotransmitters in the nervous system in addition to acting as hormones when released into the blood. 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. Some peptide/protein hormones (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.

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