AHSP and endothelial dysfunction: This finding may be due to endothelial dysfunction contributing towards an imbalance of bioavailable constrictor factors (ET-1, thromboxane A2, reactive oxygen species, and prostaglandin) which predominate over endothelium derived relaxing factors (nitric oxide (NO), prostacyclin ( PGI2) and endothelium derived relaxing factor (EDRF)).