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Vasopressin (AVP) Antidiuretic hormone
💧 Arginine Vasopressin (AVP) = also called Antidiuretic Hormone (ADH). Key roles: 🧠 hypothalamus synthesis ➝ 🩸 posterior pituitary release ➝ 💧 water reabsorption + 💢 vasoconstriction.
ℹ️ About
- 🧠 Synthesised in the magnocellular neurons of the hypothalamic supraoptic nucleus.
- 🔄 Processed into a cyclic nonapeptide.
- 📈 Released in response to ↑ plasma osmolality or ↓ blood pressure.
- 💢 Acts as a vasoconstrictor (V1).
- 💧 Increases water uptake (V2) at the kidney collecting ducts ➝ raises BP.
- ➡️ Stored & secreted from the posterior pituitary.
💊 Indications & Doses
- 🩸 Variceal bleed: Vasopressin 20 U IV over 15 min. ⚠️ Caution in asthma, angina, PVD.
- ❤️ Cardiac arrest: Vasopressin 40 U IV stat (no proven advantage over adrenaline).
- 🚰 Pituitary diabetes insipidus: 5–20 U IM/SC every 4h.
⚡ Stimuli for Vasopressin Release
- 📊 Primary: ↑ plasma osmolality (osmoreceptors).
- 🩸 ↓ blood pressure (baroreceptors).
- 💧 ↓ blood volume (volume receptors).
- Other triggers ➝ pain, nausea, opiates, surgery, exercise.
📡 Vasopressin Receptors
- 💢 V1 receptors: On vascular smooth muscle ➝ vasoconstriction via IP3 pathway. Helps maintain SVR in hypovolaemic shock.
- 💧 V2 receptors: In collecting ducts ➝ aquaporin insertion (cAMP pathway) ➝ ↑ water reabsorption ➝ ↑ blood volume, CO, arterial pressure.
⚠️ Excess ADH
- ⚡ Causes hyponatraemia (water retention dilutes plasma sodium).
- Seen in 💔 heart failure and in SIADH (Syndrome of Inappropriate ADH Secretion).
📚 References
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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