INTRODUCTION
Male pattern hair loss (MPHL), also known as androgenic
alopecia (AGA), is a progressive form of non-scarring hair loss with characteristic thinning/loss affecting the frontal, temporal, and vertex areas of the scalp.1,2 Diagnosis is made by clinical evaluation of the scalp and a thorough
medical history evaluation.3 During the term of normal hair growth, 85% to 90% of the hair follicles are in a growth phase (anagen) which lasts for 2 to 7 years, and then they decelerate
during a 2 to 3 week transition phase (catagen) when the hair follicle matrix cells associated with the dermal papilla (DP) undergo apoptosis (cell death). The remaining 10% to 15% of the hair follicles have progressed beyond anagen/catagen, into a rest phase (telogen). Telogen lasts for up to 3 months, and concludes with shedding of the hair shaft as growth of a new hair is initiated.4
Androgenic alopecia is characterized by the premature onset of catagen and a progressive shortening of the anagen phase. Over time this shift is reflected by accelerated hair shedding, a decreased ratio of terminal (long, thick, pigmented) hairs to vellus
(short, thin, non-pigmented hairs), and an overall reduction in hair density.5,6 AGA in men is associated with a progressive hereditary increase in conversion of testosterone to dihydrotestosterone
(DHT) by type II 5-a-reductase.7,8 When androgen receptors of the DP-associated cells are preferentially bound by
DHT, absorption of vital nutrients is blocked and hair matrix cell proliferation becomes inhibited. This malnourishment is believed
to trigger the premature onset of catagen, cell apoptosis, and progressive shortening of the anagen phase.9-11 Microinflammation
and altered prostaglandin metabolism within the hair follicle are also believed to contribute to premature DP apoptosis and follicular miniaturization by causing fibroplasia of the dermal sheath surrounding the hair follicle.12
Androgenic alopecia is the most common form of alopecia and is estimated to affect half of all men in the United States.13 Typical
onset occurs between 30 and 40 years of age, and by the age of 70 years up to 85% of men may be affected.13,14 Although hair loss is primarily a cosmetic concern, hair contributes to outward
appearance and social confidence, and patients seeking treatment for AGA are motivated by the psychological distress and negative impact that hair loss has on self-esteem and social self-confidence.15 Currently, topical minoxidil (2% solution and 5% solution or foam) and oral finestramide (1mg) are the only US Food and Drug Administration (FDA)-approved medications for the treatment of male AGA.16,17 Minoxidil’s mode of action is androgen independent, and believed to promote hair growth by promoting the production of vascular endothelial growth factor, increasing the production of anti-inflammatory prostaglandin
E2 (PGE2), and lengthening the duration of the anagen