eli5: angiotensin renin aldosterone system

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How does it work? I have a vague understanding of the hormones involved but why is it important and what can happen if something affects it?

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The top level of that system is this. A series of products in the body cause vasoconstriction and this increases blood pressure.

The medication interferes with the sequence. Your body uses enzymes to convert T1 to T2. The medication blocks the renin angiotensin converting enzyme. So the process does not function normally.

**Renin** is released because of low blood pressure (hypotension) or low sodium (hyponatremia). Renin converts Angiotensinogen (-ogen meaning it is waiting to be activated into its active form) into Angiotensin I. Angiotensin I is converted into Angiotensin II by Agiotensin Converting Enzyme (ACE). ACE is found primarily in pulmonary (lung) epithelium. Angiotensin II then stimulates the production of Aldosterone in the Adrenal Cortex (the little organ that sits on top of each kidney). Aldosterone will now (finally) be able to correct for the hypotension and low sodium.

The mechanism is kinda complicated if you don’t have a biochemistry or medical background, but the ELI5 for it is this. Aldosterone affects a transporter that makes it so we put less sodium in our pee. Water loves sodium, and so more sodium being reabsorbed rather than urinated out = more water being reabsorbed too. More water volume leads to more blood volume, and that leads to a higher blood pressure.

Increased Renin, and therefore, eventually, Aldosterone, leads to increased sodium reabsorption, water reabsorption, potassium excretion, and increased blood pH (metabolic alkylosis)

Many things can go wrong. Google Hereditary Angioedema, Primary Hyperaldosteronism, and read about the effects of ACE inhibitors, Angiotensin II receptor blockers, and Renin analogues to learn more. That’s just naming a few issues