Posterior pituitary — vasopressin release
Pituitary · ADH V2 kidney V1a vessels
Nerve terminals in the neurohypophysis release stored vasopressin directly into the systemic circulation on depolarisation. V2 receptors give antidiuresis, V1a receptors vasoconstriction.
Traced from the start
- Supraoptic and paraventricular magnocellular neurones
- Posterior pituitary — vasopressin release
Detail
- Stimuli
- Rising osmolality, hypovolaemia, nausea, pain, opioids, nicotine, positive pressure ventilation
- Inhibited by
- Alcohol, falling osmolality, atrial natriuretic peptide
- V2 elsewhere
- Desmopressin releases von Willebrand factor and factor VIII from endothelium — used in mild haemophilia A, von Willebrand disease and uraemic bleeding
- Drugs
- Tolvaptan blocks V2; terlipressin is a V1 agonist for variceal bleeding and hepatorenal syndrome
When it goes wrong
Small cell lung carcinoma, pneumonia, meningitis, SSRIs, carbamazepine or postoperative pain
SIADH: euvolaemic hyponatraemia with inappropriately concentrated urine while plasma is dilute
Head injury or pituitary surgery damaging the tract
Arginine vasopressin deficiency: dilute polyuria and thirst, with dangerous hypernatraemia only when access to water is lost
Practise this structure
1 question in the bank tagged Antidiuretic Hormone.