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Peptide Hormones
5.3.1 Definition
Peptide hormones are short chains of amino acids that act as chemical messengers, regulating physiological processes by binding to specific receptors on target cells. They are typically synthesized and secreted by endocrine glands and play essential roles in metabolism, growth, reproduction, and homeostasis.
5.3.2 Mechanisms of Action
Receptor Binding: Peptide hormones bind to cell surface receptors (usually G-protein coupled receptors or receptor tyrosine kinases) because they cannot cross the lipid bilayer.
Signal Transduction: Binding triggers intracellular signaling cascades, often involving second messengers like cAMP, IP3, or calcium ions.
Physiological Effects: These signaling pathways regulate gene expression, enzymatic activity, ion transport, and cellular metabolism.
5.3.3 Examples
Insulin: regulates glucose uptake and metabolism.
Glucagon: raises blood glucose by stimulating glycogen breakdown.
Adrenocorticotropic hormone (ACTH): stimulates cortisol production in the adrenal cortex.
Growth hormone (GH): promotes growth and metabolic regulation.
Oxytocin: regulates childbirth and social bonding.
5.3.4 Advantages
High specificity for their target cells and receptors.
Rapid physiological effects due to signal amplification.
Can be synthetically produced for therapeutic purposes.
Modifiable to enhance stability, half-life, and delivery.
5.3.5 Challenges
Short half-life due to enzymatic degradation in circulation.
Cannot be administered orally because digestive enzymes degrade them.
Potential for off-target effects if receptor specificity is altered.
Complex synthesis required for therapeutic analogs with modifications.
5.3.6 Applications
Therapeutic use: insulin, glucagon, and synthetic analogs for diabetes management.
Reproductive health: gonadotropin-releasing hormone (GnRH) analogs for fertility treatments.
Growth and metabolism: growth hormone therapy in deficiencies.
Research tools: study of endocrine pathways, receptor function, and intracellular signaling.
5.3.7 Conclusion
Peptide hormones are essential regulators of physiology, acting through highly specific receptor-mediated pathways. Their therapeutic analogs have revolutionized treatments for metabolic, growth, and reproductive disorders, while their study continues to provide insights into cell signaling, endocrine regulation, and systemic homeostasis.
5.3.1 Definition
Peptide hormones are short chains of amino acids that act as chemical messengers, regulating physiological processes by binding to specific receptors on target cells. They are typically synthesized and secreted by endocrine glands and play essential roles in metabolism, growth, reproduction, and homeostasis.
5.3.2 Mechanisms of Action
Receptor Binding: Peptide hormones bind to cell surface receptors (usually G-protein coupled receptors or receptor tyrosine kinases) because they cannot cross the lipid bilayer.
Signal Transduction: Binding triggers intracellular signaling cascades, often involving second messengers like cAMP, IP3, or calcium ions.
Physiological Effects: These signaling pathways regulate gene expression, enzymatic activity, ion transport, and cellular metabolism.
5.3.3 Examples
Insulin: regulates glucose uptake and metabolism.
Glucagon: raises blood glucose by stimulating glycogen breakdown.
Adrenocorticotropic hormone (ACTH): stimulates cortisol production in the adrenal cortex.
Growth hormone (GH): promotes growth and metabolic regulation.
Oxytocin: regulates childbirth and social bonding.
5.3.4 Advantages
High specificity for their target cells and receptors.
Rapid physiological effects due to signal amplification.
Can be synthetically produced for therapeutic purposes.
Modifiable to enhance stability, half-life, and delivery.
5.3.5 Challenges
Short half-life due to enzymatic degradation in circulation.
Cannot be administered orally because digestive enzymes degrade them.
Potential for off-target effects if receptor specificity is altered.
Complex synthesis required for therapeutic analogs with modifications.
5.3.6 Applications
Therapeutic use: insulin, glucagon, and synthetic analogs for diabetes management.
Reproductive health: gonadotropin-releasing hormone (GnRH) analogs for fertility treatments.
Growth and metabolism: growth hormone therapy in deficiencies.
Research tools: study of endocrine pathways, receptor function, and intracellular signaling.
5.3.7 Conclusion
Peptide hormones are essential regulators of physiology, acting through highly specific receptor-mediated pathways. Their therapeutic analogs have revolutionized treatments for metabolic, growth, and reproductive disorders, while their study continues to provide insights into cell signaling, endocrine regulation, and systemic homeostasis.