PITUITARY-ADH

SUMMARY

1. Secreted by the posterior pituitary.

2. The threshold is increased in chornic hypervolemia & HTN (ADH is released at a higher osmolality, hence more water is lost); decreased in pregnancy & PMS.

3. Volume contraction increases ADH secretion & decreased renal reponse threshold, hence conserving water.

4. Serum osmolality = 2[Na] + (Glucose/18) + (BUN/2.8).

5. Thirst begins when serum osm > 295 mOsm/L.

6. Dehydration and hypovolemia increases thirst and the secretion of ADH, but only in extreme circumstances such as shock. Mutation in V2 receptor (which binds ADH) leads to nephrogenic diabetic insipidus.

7. ADH is also released in response to non-osmotic factors; the most potent of these is nausea.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].