According to a collaborative study between the University of Texas Medical Center and UCSF Medical Center that was published in the Journal of the American Geriatric Society in June of 2014, people over the age of 65 who are treated with thiazide diuretics (such as HCTZ -- which is hydrochlorthiazide -- or Hygroton), are in danger of developing several metabolic defects.
This study pointed out three metabolic defects that include hyponatremia (low sodium), hypokalemia (low potassium), and acute kidney injury where there was at least a 25% decrease in kidney function. Wow! And there's more that was not included in this article such as causing high cholesterol and uric acid (predisposes to gout), insulin resistance (predisposes to type 2 diabetes), and low magnesium!
And this is the first drug of choice according to the major medical associations that set the guidelines for treating high blood pressure! Wow! It makes you wonder about the rest of the drugs used in managing this disease. Lifestyle remains the best treatment for managing hypertension.