Primary Aldosteronism in a Patient With an Adrenal Macroadenoma and Clinically Important Cortisol Cosecretion

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Unlike aldosterone-producing adenomas (APAs) that can be <1 cm in diameter and cause the full syndrome of primary aldosteronism (PA), clinically important cortisol-secreting adenomas require a “big factory” (e.g., typically >2 cm in diameter). Thus when a patient with PA has a large adrenal adenoma (>1.5 cm), clinicians should screen for cortisol cosecretion. If autonomous cortisol cosecretion is present in a patient with PA who has a unilateral adrenal macroadenoma, then adrenal venous sampling (AVS) is not needed. Usually in this setting the macroadenoma is cosecreting aldosterone and cortisol. However, even if the patient has PA caused by bilateral idiopathic hyperplasia (IHA) or a contralateral adrenal microadenoma, we do not have a good long-term viable medical treatment option for hypercortisolism, whereas mineralocorticoid receptor antagonists are an excellent treatment option for PA if it proves to persist following unilateral adrenalectomy. Thus if AVS is performed in the setting described in the preceding text, the findings do not guide surgical management.

Case Report

The patient was a 46-year-old man with a 15-year history of hypertension, which accelerated 10 years ago. He was treated with a three-drug program: calcium channel blocker (amlodipine 10 mg daily), combined β- and α-adrenergic blocker (labetalol 400 mg twice daily), and an angiotensin-converting enzyme inhibitor (enalapril 10 mg daily). Blood pressure control was not optimal. He was referred to Mayo Clinic for AVS. At the time of referral to Mayo Clinic he was taking 40 mEq of potassium chloride daily in an effort to maintain a normal serum potassium concentration. Beyond hypertension and hypokalemia, the patient was healthy. His body mass index was 29.2 kg/m ² . He had no signs or symptoms of overt Cushing syndrome. He did not have diabetes mellitus or osteoporosis. He had two first-degree relatives who had been diagnosed with hypertension.

INVESTIGATIONS

The baseline laboratory test results are shown in Table 12.1 . The patient had positive case detection testing for PA with plasma aldosterone concentration (PAC) >10 ng/dL and plasma renin activity (PRA) <1.0 ng/mL per hour. In addition, PA was confirmed because when a patient has spontaneous hypokalemia and a PAC >20 ng/dL, there are no other differential diagnostic possibilities beyond PA. ^, Thus formal confirmatory testing with oral sodium loading or a saline infusion test was not needed for this patient. A baseline 24-hour urine for sodium showed that this patient was on a daily high sodium diet, which was contributing to his resistant hypertension and hypokalemia. Serum corticotropin (ACTH) was undetectable and the serum dehydroepiandrosterone sulfate (DHEA-S) concentration was low-normal, and cortisol did not suppress with an overnight 8-mg dexamethasone suppression test (DST) (see Table 12.1 ).

TABLE 12.1

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