Contributor: Nick Tsipis, MD Educational Pearls: Congenital adrenal hyperplasia (CAH) is a group of enzyme deficiencies in the adrenals leading to a deficiency of hormones normally synthesized by the adrenals (mineralocorticoids, glucocorticoids, androgens) 21-hydroxylase is most commonly the deficient enzyme. 21-hydroxylase is needed to produce aldosterone and cortisol, and those with chronic cortisol deficiencies need daily steroid replacement Aldosterone, made in the kidney as part of the renin-angiotensin-aldosterone system (RAAS), increases blood pressure via salt and water retention to maintain adequate organ perfusion Adrenal crisis results in a loss of cortisol leading to hypoglycemia and potential CNS depression with hypotension, hypoglycemia, and hyponatremia Patients in adrenal crisis need salt, volume, and glucose replacement References Martin-Grace, J., et al. Adrenal insufficiency: physiology, clinical presentation and diagnostic challenges. Clin Chim Acta. 2020 Feb 6.  Dineen, R., Thompson, C.J., Sherlock, M. Adrenal crisis: prevention and management in adult patients. Ther Adv Endocrinol Metab. 2019 Jun 13;10:2042018819848218. El-Maouche, D., Arlt, W., Merke, D.P. Congenital Adrenal Hyperplasia. Lancet. 2017 Nov 11;390(10108):2194-2210.   Summarized by Jackson Roos, MS3 | Edited by Erik Verzemnieks, MD