There are many causes of hair loss in men and women, including disease, nutritional deficiency, hormone imbalance, and stress. However, by far the most common cause is what is called adrogenetic alopecia. Alopecia is simply the medical term for hair loss. Androgenetic refers to the fact that both a genetic predisposition to balding, and the influence of androgens, or male hormones, play a part in this type of hair loss. In fact, there is a third factor, which is the passage of time, or aging. In other words, in order for androgenetic alopecia to occur, there must be: * a genetic propensity for balding * the presence of androgens, or male hormones * enough aging time to allow the first two factors to exert their influence on the hair follicles Genetics Genetics is not always simple, and such is the case with balding. Just the presence or absence of balding in one's parents or grandparents, on either the mother's or father's side, is not necessarily predictive of one's likelihood of balding. Certainly, if a man's father is completely bald, and this man begins to rapidly lose hair in his early twenties, it's a safe bet that he will develop extensive balding at some point. In short, it's very hard to accurately predict who will go bald and how rapidly. This inherent uncertainly about the progression of balding is of utmost importance in planning surgical hair restoration, as we will see in later sections. We must always plan for a "worst case scenario" in order to give patients the best possible results in the long term, as well as in the short term. Anything less is irresponsible. Androgenic Hormones All normal men and women produce "male" hormones. The most common of these are testosterone, androsteinedione, and dihydrotestosterone (DHT). Androgens are produced by the testicles and adrenals in men, and by the ovaries and adrenal glands in women. These hormones are quite important in both sexes, but occur in different concentrations, being much more predominant in males than in females. This, in part, is responsible for the typical differences between the genders. It is the exposure of the hair follicles to DHT, in a genetically susceptible person, over a period of time, which leads to androgenetic alopecia, or male and female pattern baldness. How does this exposure to DHT occur?