- Also known as Vasopressin
- Synthesized in the hypothalamus:
- Supraoptic nucleus → mainly ADH
- Paraventricular nucleus → mainly Oxytocin
- Stored and released by the posterior pituitary
- Functions via V1 and V2 receptors
Functions
| Receptor Type | Location | Function |
|---|---|---|
| V1 receptors | Vascular smooth muscle | Vasoconstriction → ↑ Blood Pressure |
| V2 receptors | Kidney (Collecting ducts) | ↑ Water reabsorption via aquaporin-2 channels → ↓ Plasma osmolality |
Regulation
| Stimulus for Secretion | Inhibition |
|---|---|
| ↑ Plasma osmolality | ↓ Plasma osmolality |
| ↓ Blood volume / BP | Alcohol intake |
| Pain, stress, nausea | — |
Clinical Correlations
| Disorder | Pathophysiology | Key Findings |
|---|---|---|
| Central Diabetes Insipidus | ↓ ADH secretion (hypothalamic/post-pituitary damage) | Polyuria, polydipsia, hypernatremia; responds to Desmopressin (DDAVP) |
| Nephrogenic Diabetes Insipidus | ADH receptor defect (V2) in the kidneys | Polyuria, polydipsia, no response to desmopressin |
| SIADH (Syndrome of Inappropriate ADH) | ↑ ADH secretion | Hyponatremia, low plasma osmolality, high urine osmolality |
Learning Objectives
By the end of this topic, you should be able to:
- Explain ADH regulation mechanisms.
- Recognize clinical disorders associated with ADH imbalance.
