Minoxidil (brand name Rogaine) is known to be one of only two medications officially approved for hair loss treatment (the other being Finasteride). However, even as of 2014, scientists do not know the exact mechanism via which Minoxidil has a positive effect on hair growth. The original use of Minoxidil was as an oral medication for high blood pressure. The side effect of hypertrichosis (excessive body hair) led to its becoming a popular treatment option for hair loss.
To date, the main hypothesis about how Minoxidil works relates to its vasodilatory, potassium channel opening and increased blood flow effects/properties. There are also other theories about how Minoxidil helps grow scalp hair, and below I list all of the main ones. It should be noted that Minoxidil, besides prolonging the growth phase of the hair cycle, has also been shows to increase the diameter of existing hair follicles. According to a study from 1988, seven subjects who received t a 5 percent dose of minoxidil had a mean hair shaft diameter of 0.029 mm before treatment, which then increased to 0.043 mm at 12 weeks.
- In 1997, researchers found that Minoxidil increased prostaglandin synthesis (more specifically, prostaglandin synthase-1 = PGHS-1) in cultured dermal papilla cells. In more recent years, the issue of prostaglandins and hair loss has garnered a great deal of attention and you can search for “PGE2” on this blog to learn more.
- A French study from 1998 is among many that has found that Minoxidil upregulates growth factors, in particular vascular endothelial growth factor (VEGF).
- A 2001 study found that the positive effect of Minoxidil on hair is mediated by adenosine.
- An excellent article from 2008 on hair loss medical treatments by Dr. Nicole Rogers and Dr. Marc Avram that discusses Minoxidil in detail. They mention that one of the main effects of Minoxidil is angiogenesis and increased blood flow in the area of application. They also discuss the enhanced cell proliferation and DNA synthesis effects on Minoxidil that might be benefiting hair growth.
- In 2011, South Korean researchers found that Minoxidil activated the β-catenin pathway in human dermal papilla cells and therefore extended the anagen (growth) phase of the hair cycle.
- In April 2014, Taiwanese researchers came up with yet another reason as to why Minoxidil works, concluding that Minoxidil may suppress androgen receptor-related functions. i.e., the drug has anti-androgenic properties. Their conclusion is especially interesting:
The current findings provide evidence that minoxidil could be used to treat both cancer and age-related disease, and open a new avenue for applications of minoxidil in treating androgen-AR pathway-related diseases.