The most important regulator of electrolyte concentrations is aldosterone, which is a steroid produced by the adrenal glands in the kidneys. It balances electrolytes by stimulating the kidneys and colon to increase the absorption of sodium, while releasing excess potassium. The kidney hormone renin stimulates the release of aldosterone in response to a high potassium level, lowered blood flow to the kidneys or falling blood pressure.
High levels of aldosterone occur when the body is trying to conserve fluid and sodium. When aldosterone levels get too high, which occurs under stress, the level of potassium falls, blood pressure increases and symptoms such as muscle cramps, muscle weakness and numbness occur. Once sodium levels are corrected and the body is rehydrated, the renin level decreases, and the kidneys secrete progressively less aldosterone.
However, when the levels of aldosterone become too low, the kidneys excrete too much salt, which leads to high potassium levels, low blood pressure and low blood volume. Frequent urinating, sweating and feeling thirsty are symptoms of low aldosterone. Addison's disease, which is a loss of adrenal function, can cause low levels of aldosterone as well as the failure of an enzyme used in the production of the hormone.