A 51-yr-old woman is presented with the typical clinical and biochemical picture of primary aldosteronism. During two periods of treatment with spironolactone the blood pressure normalized and plasma potassium increased to normal levels. In spite of an increase in plasma renin activity from undetectable to elevated levels the plasma concentration of aldosterone decreased gradually from about 210 to 40–70 pg/ml. Similarly, the aldosterone secretion rate decreased from 352 to 68 μg/24 hr after 4 months of treatment with spironolactone. An ACTH stimulation test performed during spironolactone treatment led to a minor increase only in the plasma cortisol level. Adrenal photoscintigraphy with 131I-iodocholesterol indicated the presence of a tumor on the right side which was confirmed during operation and the adrenal was removed. The histological examination revealed numerous laminated acidophilic cytoplasmatic inclusions (spironolactone bodies) in the adjacent adrenal tissue, but only in a few cells of the adenoma. Nine months after operation the patient is healthy, without any medication, and with normal plasma levels of aldosterone, cortisol and renin activity. It is concluded that spironolactone inhibits the synthesis of aldosterone and presumably also cortisol. It is suggested that the clinical effect of spironolactone in hypertension is due to a combination of inhibited synthesis and peripheral antagonism of the action of mineralocorticoids.
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Sundsfjord et al. (1974) studied this question.