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In primary aldosteronism, also known as Conn's syndrome, there is an abnormal secretion of aldosterone due to an adrenal adenoma or hyperplasia of the adrenal glands. This condition directly causes increased levels of aldosterone in the bloodstream. Aldosterone acts to promote sodium retention and potassium excretion, leading to hypertension and hypokalemia.

As aldosterone levels rise due to the presence of an adrenal tumor or overactivity of the adrenal cortex, the renin-angiotensin-aldosterone system (RAAS) is affected. Increased aldosterone typically leads to feedback inhibition of renin production, resulting in decreased renin levels. This characteristic pattern of increased aldosterone and decreased renin levels is crucial in diagnosing primary aldosteronism.

In contrast, secondary aldosteronism is usually associated with conditions that lead to activation of the RAAS due to factors like renal artery stenosis or heart failure, where renin levels are often elevated. Hypomagnesemia does not directly cause elevated aldosterone levels but can influence other electrolyte imbalances. Neuroblastoma can cause ectopic production of catecholamines but is not associated with the specific increase in aldosterone or decrease in renin levels as seen in primary aldosteronism.