Preclinical studies showed the Nitric Oxide (NO) gel significantly promoted hair follicle formation and growth in both rat and mouse models. The NO gel induced major physiological, developmental, and structural changes in the skin of mammals to increase the number of hair follicles, follicle stem cell development and regeneration as well as hair shaft elongation, and accelerated hair growth rate. Based on our animal model findings, the investigators hypothesize that the nitric oxide releasing gel could be used as a medical treatment for hair growth in humans. The objective of this trial is to evaluate the safety and efficacy of this NO gel (XN-001), in comparison with a placebo gel in subjects in a 24-week treatment schedule.