Effects of guanfacine on growth hormone, prolactin, renin, lipoproteins and glucose in essential hypertension.

The effect of single-dose, short-term (6 weeks) and long-term (7 years) guanfacine therapy on various endocrine and metabolic parameters was evaluated in patients with moderate essential hypertension (WHO phase I and II). A single oral dose (2 mg) of guanfacine did not affect the secretion of growth hormone but produced a prompt decrease in blood pressure (BP) levels. Short-term treatment decreased BP and heart rate, and also produced a marked (p less than 0.001) fall in urinary excretion of norepinephrine and serum prolactin levels. Short-term therapy did not affect growth hormone or renin levels. A mean daily dose of 2.8 mg of guanfacine maintained normal BP levels in 22 patients during the long-term follow-up study. In addition, treatment produced a progressive decrease in prolactin, renin, total cholesterol and triglyceride levels, but did not change growth hormone values or oral glucose tolerance test results. The cumulative incidence of cardiovascular complications was significantly lower (p less than 0.001) in guanfacine-treated patients than in a matched control group. The most significant difference was the absence of fatal complications in the guanfacine-treated patients. The present results support the theory that decreased morbidity and mortality in patients treated with guanfacine may depend not only on its important antihypertensive activity, but also on its beneficial effect on known cardiovascular risk factors.