The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil is a potassium channel agonist. It contains the chemical structure of nitric oxide (NO), a blood vessel dilator, and may be a nitric oxide agonist. This appears to explain its vasodilatory effects, but may also be linked to minoxidil's ability to stimulate hair growth and treat hair loss. Since minoxidil is a nitric oxide-related compound, it was suspected to act via activation of guanylate cyclase, an enzyme involved in vasodilation, however there are no reports of cGMP or PKG activation to date.