<qa>  What is the lowest dose of BH4?We, the researchers at Emory University, will recruit patients with hypertension and randomize them to various doses of BH4 to find out what the lowest dose is that produces a significant response This dose will then be used in patients with hypertension who will be randomized to BH4 or a placebo. Patients will be followed for blood pressure response and for markers of endothelial function using ultrasound and for markers of inflammation using blood samples. 