Primary Aldosteronism Common in Patients With Type 2 Diabetes and Resistant Hypertension

July 3, 2007 — In patients with type 2 diabetes and resistant hypertension, primary aldosteronism has a prevalence of 14%, according to the results of a study published in the July issue of Diabetes Care. The authors recommend screening for aldosteronism in these patients who are taking 3 or more antihypertensive drugs.
"Despite the high prevalence of hypertension in patients with type 2 diabetes, the prevalence of primary aldosteronism in this population has not been determined," write Guillermo E. Umpierrez, MD, from Emory University School of Medicine in Atlanta, Georgia, and colleagues. "Primary aldosteronism was previously believed to account for < 1% of hypertensive patients; however, recent studies applying the plasma aldosterone (PAC)-to plasma renin activity (PRA) ratio as a screening test have reported a much higher prevalence of this disease, accounting for 10 - 32% of the patients with essential hypertension and 50% of patients with nondiuretic-induced hypokalemia."
In this study, 100 participants with type 2 diabetes and resistant hypertension, defined as blood pressure greater than 140/90 mm Hg despite treatment with at least 3 antihypertensive agents, were screened for primary aldosteronism by measuring the PAC/PRA ratio. Of the 100 participants, 93 were African Americans.
In participants with a PAC/PRA ratio greater than 30 ng/mL/hour, confirmatory salt load testing was performed. Primary aldosteronism was defined as a 24-hour urine aldosterone level of 12 µg or greater during the third day of the oral salt load or a PAC of 5 ng/dL or greater after the 4-hour intravenous saline load.
The PAC/PRA ratio was greater than 30 ng/mL/hour in 34 participants, and there was a confirmed diagnosis of primary aldosteronism for 14 participants (14%; 95% confidence interval, 7.2 - 20.8). Participants with and without primary aldosteronism did not differ in age, glycemic control, and number of antihypertensive drugs.
Compared with patients without primary aldosteronism, those with primary aldosteronism had lower serum potassium levels (3.7 ± 0.4 vs 4.0 ± 0.4 mmol/L; P = .012), higher PACs (15.6 ± 8 vs 9.1 ± 6 ng/dL; P = .0016), and higher PAC/PRA ratios (98 ± 74 vs 21 ± 30 ng/mL/hour; P < .001).
"Primary aldosteronism is common in diabetic patients with resistant hypertension, with a prevalence of 14%," the authors write. "Our results indicate that diabetic subjects with poorly controlled hypertension who are taking ≥ 3 antihypertensive drugs should be screened for primary aldosteronism."
Study limitations include a relatively small number of subjects, most subjects being African American, and the lack of a control group without diabetes.
"These results are of great clinical importance because patients with primary aldosteronism have a high incidence of renal and cardiovascular complications and increased mortality and because aldosterone blockade can ameliorate renal and cardiovascular complications in patients with hypertension and with primary aldosteronism," the authors conclude.
Dr. Umpierrez is supported by research grants from the American Diabetes Association, the American Heart Association, and the National Institutes of Health and by a General Clinical Research Center Grant. The costs of publication of the original article were defrayed in part by the payment of page charges, which mandated its being marked "advertisement."
Diabetes Care. 2007;30:1699-1703.