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'''Androgenetic Alopecia (AGA)'''
'''Androgenetic Alopecia (AGA)'''


Androgenetic alopecia (AGA) is an androgen-dependent condition of progressively thinning of the scalp hair. AGA is also referred to as male-pattern hair loss or baldness (MPB) and  female-pattern hair loss in women. It is characterized by progressive shortening of the duration of anagen with successive hair cycles, leading to decreased numbers of hair in anagen at any given time, and aggressive follicular miniaturization with conversion of terminal to vellus-like follicles <ref name="ten"> Paus, R., Cotsarelis, G. (1999).The biology of hair follicles. N. Engl. J. Med., 34, 491–497. </ref> The reason for the use of finasteride to treat AGA in men is based on the absence of AGA in men with congenital deficiency of type 2 5α-reductase, and the presence of increased 5α-reductase activity and DHT levels in balding scalp <ref name="eleven"> Yamana, K., Labrie, F., Luu-The, V. (2010). Human type 3 5α-reductase is expressed in peripheral tissues at higher levels than types 1 and 2 and its activity is potently inhibited by finasteride and dutasteride. Hormone Molecular Biology and Clinical Investigation. 2 (3). doi:10.1515/hmbci.2010.035. </ref>. This condition is caused by a build up of DHT in tissues, which in the case of MPB, is the scalp. The build up of DHT causes androgen-dependent miniaturization of scalp hair follicles. Testosterone is the primary androgen in the body, but to be maximally active in scalp hair follicles it must be converted to dihydrotestosterone (DHT) by the enzyme 5α-reductase. Inhibition of the enzyme with Finasteride has been shown to reduce both serum and scalp skin DHT levels in balding men. In some patients, hair regrowth can occur.<ref name="twelve"> Olsen, E. A., Hordinsky, M., & Whiting, D., et al. (2006, December). </ref> Side effects from Finasteride include but are not limited to, decreased sexual ability and desire. <ref name="thirteen"> Leyden, James et al.(June 1999)."Finasteride in the treatment of men with frontal male pattern hair loss." Journal of the American Academy of Dermatology. Volume 40 , Issue 6 , 930 - 937 </ref>  
Androgenetic alopecia (AGA) is an androgen-dependent condition of progressively thinning of the scalp hair. AGA is also referred to as male-pattern hair loss or baldness (MPB) and  female-pattern hair loss in women. It is characterized by progressive shortening of the growing phase in hair follicles, anagen phase, during successive hair growth cycles, leading to decreased numbers of hair in anagen at any given time, and aggressive follicular miniaturization with conversion of terminal to vellus-like follicles <ref name="ten"> Paus, R., Cotsarelis, G. (1999).The biology of hair follicles. N. Engl. J. Med., 34, 491–497. </ref> Finasteride can treat AGA in men who lack AGA due to congenital deficiency of type 2 5α-reductase, the presence of increased 5α-reductase activity or DHT levels in balding scalp <ref name="eleven"> Yamana, K., Labrie, F., Luu-The, V. (2010). Human type 3 5α-reductase is expressed in peripheral tissues at higher levels than types 1 and 2 and its activity is potently inhibited by finasteride and dutasteride. Hormone Molecular Biology and Clinical Investigation. 2 (3). doi:10.1515/hmbci.2010.035. </ref>. This condition is caused by a build up of DHT in tissues (scalp). The build up of DHT causes androgen-dependent scalp hair follicles to shrink. Testosterone converts dihydrotestosterone (DHT) by the enzyme 5α-reductase to be maximally active in scalp hair follicles. Inhibition of the 5α-reductase enzyme with Finasteride has been shown to reduce both serum and scalp skin DHT levels in balding men. <ref name="twelve"> Olsen, E. A., Hordinsky, M., & Whiting, D., et al. (2006, December). </ref> Side effects from Finasteride include but are not limited to, decreased sexual ability and desire. <ref name="thirteen"> Leyden, James et al.(June 1999)."Finasteride in the treatment of men with frontal male pattern hair loss." Journal of the American Academy of Dermatology. Volume 40 , Issue 6 , 930 - 937 </ref>  




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