A receding hairline refers to the progressive hair loss experienced by men as a part of male pattern baldness. Often, it begins as a thinning of the hair, first on either side of the forehead. This progresses to become a bald patch on the top of the head. The likelihood that a man will experience a receding hairline is determined by several factors, with genetics playing the biggest role. Most men with receding hairlines are over 25 years of age, but some start to notice thinning in the teen years.
The main direct cause of receding hairlines is the hormone known as dihydrotestosterone, or DHT. This hormone normally acts as a sex hormone in males, spurring the development of secondary sex characteristics during puberty. Eventually, DHT outlives its usefulness and can cause unwanted side effects. Principal among these is the inhibition of hair growth.
Not all men experience a receding hairline or other ill effects from DHT activity. In some men, the production of DHT slows down naturally, rather than continuing at a high rate. In others, DHT continues to be produced in excess. In these cases, the DHT builds up in certain places in the body, including the hair follicles. When enough of the hormone binds to a hair follicle, blood flow to it is choked off, starving the hair of nutrients and eventually causing it to fall out.
If left to its own devices, a receding hairline will eventually cause permanent baldness over the whole scalp in most cases. Due to the psychological and social implications that this would have for most men, many drugs and other treatments have become available which aim to stop or reverse a receding hairline. Some of these drugs, however, have a potential for negative side effects and interactions with other drugs. Herbal remedies carry less of a risk for these things, but have not been tested and developed as extensively.
The presence of high levels of DHT is not the sole deciding factor for baldness or a receding hairline. While this condition is genetic and its expression at some point is more or less unavoidable if the gene is present, certain environmental factors can accelerate baldness in those with this hereditary trait. One example that is observed somewhat often is the effect of emotional stress, especially for long periods of time. Stress can significantly enhance the progression of a receding hairline, once it has begun. Some studies have also found a positive correlation between smoking and hair loss.