Primary hyperaldosteronism (PHA) is present in 5 to 10% of patients with high blood pressure and in 20% of patients with therapy-resisting hypertonia. For PHA screening in patients at risk, the renin and aldosterone levels in plasma are determined and the aldosterone/renin ratio is.
Low renin values are also associated with hyperplasia of the adrenal cortex with aldosterone overproduction and the rare Liddle syndrome, a hereditary form of high blood pressure, caused by the mutation of an epithelial sodium channel of the kidney tubules: Water and sodium resorption are increased, renin and aldosterone plasma levels are lowered.
Renin can be determined as enzymatic plasma-renin activity (PRA). PRA measurement is precise since the angiotensinogen concentration is taken into account.
PRA is determined in two steps. First, the angiotensinogen contained in the plasma sample is converted into Ang I in vitro. Then, the resulting Ang I is measured in an enzyme immunoassay.
Circadian rhythms do not affect the renin values. These increase with low sodium supply, with physical activity, during pregnancy and with intake of diuretics. Renin levels decrease with age and also with impaired kidney function and with intake of beta blockers.