Study objective: To determine whether changes in serum glucose, serum potassium, and plasma insulin levels are correlated in a cohort of hypertensive patients.
Design: Prespecified subgroup analysis of results from a prospective, multicenter, randomized, open-label, parallel-group study. Setting. Primary care clinics at three tertiary care medical centers.
Patients: Community-based ambulatory population of 202 patients (age range 17-65 yrs) with a new diagnosis of hypertension, untreated hypertension, or known hypertension, who were previously treated with fewer than three antihypertensive drugs and had no evidence of cardiovascular disease or diabetes mellitus. Intervention. Monotherapy with oral hydrochlorothiazide 12.5 or 25 mg/day for 9 weeks.
Measurements and main results: Fasting serum glucose, serum potassium, and plasma insulin levels were obtained at baseline (before hydrochlorothiazide therapy was started) and after 9 weeks of therapy. Significant elevations were noted in fasting serum glucose (mean +/- SD 3.42 +/- 10.38 mg/dl, p<0.0001) and plasma insulin (2.35 +/- 9.47 microU/ml, p<0.0001) levels, and a significant reduction in serum potassium level (0.30 +/- 0.44 mEq/L, p<0.0001) was noted. No significant correlation was observed between changes in fasting serum glucose and potassium levels (r = 0.022, 95% confidence interval (CI) -0.120-0.164, p=0.757) or between changes in serum potassium and plasma insulin levels (r = -0.112, 95% CI -0.256-0.037, p=0.140). Changes in serum glucose levels did not differ significantly between patients maintaining serum potassium levels of 4.0 mEq/L or greater and those with levels below 4.0 mEq/L.
Conclusion: Changes in serum potassium and serum glucose levels were not correlated in individuals receiving hydrochlorothiazide monotherapy; thus maintenance of normal potassium levels may not attenuate the risk of thiazide diuretic-induced hyperglycemia.