A 39-year-old female presents with adrenal mass, hypokalemia
A 39-year-old woman was referred for the evaluation of primary aldosterone with a history of hypertension since she was aged 17 years. She had hypokalemia over the past 4 years.
Her blood pressure was 132 mm Hg/81 mm Hg with a pulse of 83; she was taking metoprolol 50 mg twice daily, lisinopril 40 mg daily, amlodipine 10 mg daily and potassium chloride 40 mEq twice daily.
Laboratory testing showed a serum sodium 139 mmol/L; blood urea nitrogen (BUN) 10 mg/dL; creatinine 0.69 mg/dL; potassium 3 mmol/L; chloride 102 mmol/L; carbon dioxide 26.5 mmol/L; aldosterone 17 ng/dL with a plasma renin activity of 0.2 ng/mL/hour.
The serum aldosterone/plasma renin activity (PRA) ratio was elevated at 85 ng/mL/hour.
A 24-hour urine collection for aldosterone was elevated at 54.3 mcg/24 hour (reference range 2.3-21). After salt suppression (3 gm sodium chloride four times daily for 5 days), the urine aldosterone of 37.1 mcg/24 hour (reference range <5 mcg) remained elevated with a normal urinary free cortisol of 40.1 mcg/24 hour.
A CT of the abdomen with an adrenal protocol showed a normal-appearing left adrenal gland and a 2 cm × 1.9 cm right adrenal mass with low attenuation (10 Hounsfield units [HU]; Figure 1) that increased immediately after contrast infusion (27.9 HU) with a fast washout (4.1 HU) consistent with a lipid-rich adenoma.
A bilateral adrenal vein sampling was performed with continuous IV cosyntropin 50 mcg/hour. Catheters were placed in the right femoral vein and with fluoroscopic guidance to inferior vena cava (IVC), then into the right adrenal vein, right accessory hepatic vein and a right adrenal vein.
Venogram of the right adrenal vein showed multiple venous branches draping around the right adrenal mass (Figure 2).
Venous blood samples were obtained from the right and left adrenal veins and the IVC and analyzed for aldosterone and cortisol. The cortisol ratio of the right adrenal vein and the left adrenal vein were identical (see Table 1), which proves both catheters were appropriately placed and draining both adrenal glands.
Figures reprinted with permission: Stephanie L. Lee, MD, PhD
With continuous cosyntropin stimulation, the aldosterone/cortisol ratio from the right adrenal vein was higher than the left adrenal vein and the IVC (Table 1). This is consistent with a right aldosteronoma.
She had an uneventful endoscopic right adrenalectomy that showed an ovoid, well-circumscribed, yellow tumor measuring 3.5 cm × 2.1 cm × 1.3 cm within the adrenal cortex, consistent with an adrenal adenoma. Postoperative she was able to stop the potassium supplements and had a normal blood pressure with only lisinopril at 20 mg daily. Laboratory testing showed potassium 4.6 mmol/L; plasma aldosterone 1 ng/dL; PRA 5.5 ng/mL/hour; and aldosterone/renin ratio of 0.2.
Clinically, primary hyperaldosteronism (PH), or Conn’s syndrome, should be considered with antihypertensive drug-resistant hypertension associated with hypokalemia. The diagnosis can be challenging but important to diagnose because, as in the patient presented in this case, the hypertension can often be cured by surgery. There are other causes of PH that should not be treated surgically, but rather medically.
PH is caused by aldosterone-producing adenomas (APAs), aldosterone-producing renin-responsive adenomas (AP-RAs), bilateral adrenal (glomerulosa) hyperplasia or idiopathic adrenal hyperplasia (IAH), primary adrenal hyperplasia (PAH) and, rarely, familial forms of PH.
Approximately 70% of PH is due to a single adrenal cortical adenoma, and most of the rest is due to bilateral IAH. It is important to distinguish between these two subtypes of PH because the treatment of adenoma is surgery, but the treatment of choice for IAH is medical therapy with aldosterone antagonists.
When PH is suspected, a random serum aldosterone and PRA should be measured (see Table 2 on next page). A ratio of aldosterone (ng/dL)/PRA (ng/mL/hour) of more than 20 to 25 has a 95% sensitivity and a 75% specificity for PH.
The next confirmatory test is a 24-hour urinary aldosterone sodium chloride loading of more than 14 mcg/day. Rarely, in difficult borderline tests, an oral IV salt-loading protocol may be performed.
After 5 days of salt loading (10-12 g of sodium chloride), a serum for an aldosterone/PRA ratio and 24-hour collection is done for aldosterone, sodium, potassium and creatinine. The creatinine confirms adequate collection, urinary sodium of more than 250 mEq/day confirms adequate sodium load and validates the other measurements. This test is rarely done because of the significant risk for hypokalemia from the sodium load.
Initial radiologic investigation in the workup of PH is high-resolution, thin-slice (2-2.5 mm) adrenal CT scanning with contrast. Aldosteronomas tend to be small and may not always be seen on CT or MRI scans.
Characteristics of a benign adrenal mass on CT include tumors smaller than 5 cm, regular margins, no necrosis, very low CT attenuation (<20 HU) and delayed contrast washout of more than 50%. The overall sensitivity is more than 90%, but there are many false-positive scans from incidentalomas, which may be found in up to 10% of the population.
Adrenal venous sampling confirms the lateralizable excess aldosterone production and distinguishes between IAH and an aldosteronoma. The accuracy of the test is more than 95% when the procedure is technically successful. The ratio of aldosterone concentrations between the right and left adrenal veins generally exceeds 10:1.
The procedure can be complicated by venous thrombosis and adrenal hemorrhage.
Stephanie L. Lee, MD, PhD, is associate professor of medicine; associate chief, section of endocrinology, diabetes and nutrition; and associate professor of medicine at the Boston Medical Center.
For more information:
- Schwartz GL. Endocrinol Metab Clin North Am. 2011;40:279-294.
- Webb R. Ann Surg Oncol. 2011;doi:10.1245/s10434-011-2121-5.
- Zeiger MA. J Clin Endocrinol Metab. 2011;96:2004-2015.
Disclosure: Dr. Lee reports no relevant financial disclosures.