Androgenetic Alopecia, Androgenic Alopecia, or pattern baldness, has been a part of the human race for as long as we have historical records. Evolutionary evidence suggests androgenetic alopecia has been around longer than the modern human race. Our nearest non-human primate relatives, orangutans and gorillas can also develop androgenetic alopecia. Androgenetic Alopecia is a very common form of hair loss and could be described as part of our general genetic phenotype. People who do not develop Androgenetic Alopecia are in the minority. We could even say these non-bald people are the deviants from the norm! One of the first to study pattern baldness was Hippocrates who was affected himself. He was the one to name it Alopecia, as the term comes from the word «alopex», which translates from Latin as a «fox disease», so he named it after foxes loosing their fur in patches because of the annual moult. Medicine has long recognized Androgenetic Alopecia as an inherited systemic disease associated with sexual development. Ancient Greek doctors realized that male pattern baldness can develop in men of any age after puberty. They recorded that young boys castrated before puberty did not develop Androgenetic Alopecia regardless of their genetic family history. However, boys castrated during or after puberty could develop Androgenetic Alopecia. We now know that the reason for their observations is castration prepuberty stops hair follicles from being exposed to androgens made by the gonads during adolescence. Castration after puberty is too late. Once hair follicles have been exposed to androgens they are fated to become androgen sensitive and Androgenetic Alopecia can develop. Despite its standard name of “male pattern baldness” Androgenetic Alopecia is also the most common form of hair loss in women. Androgenetic Alopecia develops as a gradual reduction of scalp hair follicle size, and reduced time in the Anagen active growth phase, leading to more hair follicles in the telogen resting stage of the hair cycle. In men, the hair loss is limited to the top of the head and can involve thinning and/or receding hair lines. In women the presentation is different with just diffuse thinning over the top of the head and sometimes thinning over the entire scalp. Androgenetic Alopecia affects between 50 and 80% of Caucasian men. A rule of thumb is for men in their thirties, 30% have Androgenetic Alopecia. For men in their forties, 40% have alopecia and so on until 80% of men are affected when 80 or more years old. Different ethnic backgrounds have different susceptibility levels towards the development of Androgenetic Alopecia. The Chinese male population has a similar progressive increase in those affected with advance in age but in total baldness is much less common compared to Caucasian males. The numbers of Chinese males affected by androgenetic alopecia is approximately half that of Caucasian males. American Indians and African Americans also have a lower incidence of androgenetic alopecia compared to Caucasians. These frequency differences between races suggests genetic predisposition is important in pattern baldness susceptibility. Hair loss is first observed in women in their late twenties to early forties, somewhat later in age than first onset in men. Unlike men the frequency of women affected does not continue to increase with increasing age. After the fifth decade of life the numbers of women with Androgenetic Alopecia does not increase. Androgenetic Alopecia has been suggested to be present in the general female population at a rate anywhere between 20 to 40%. It is perhaps one of the best kept female secrets knowing the fact female Androgenetic Alopecia is apparently so common.