Prolonged Hypokalemia Following Metyrapone Treatment for Primary Bilateral Macronodular Adrenal Cortical Disease

Surgical treatment is generally the standard therapeutic regimen used for primary bilateral macronodular adrenal cortical disease (PBMACD). However, in cases for which surgery is difficult or in which there is mild cortisol hypersecretion, metyrapone treatment can be selected. Although hypokalemia has been occasionally noted following metyrapone administration for Cushing syndrome associated with an adrenal adenoma, all such cases have been reported to be transient. Hypokalemia induced by metyrapone treatment is thought to occur due to excessive suppression of cortisol secretion, resulting in overproduction of adrenocorticotropic hormone from the pituitary gland, ultimately leading to excessive production of 11-deoxycorticosterone (DOC) in the adrenal cortex. A 52-year-old man diagnosed with PBMACD and started on metyrapone treatment subsequently presented with persistent hypokalemia. Interestingly, following initiation of metyrapone, blood test findings indicated marginal changes in serum cortisol, adrenocorticotropic hormone, and dehydroepiandrosterone sulfate levels, even when DOC levels were already markedly elevated. In addition to the effects of metyrapone, the present findings suggest a unique DOC synthesis regulatory mechanism involved in the pathogenesis of PBMACD.