Androgenetic alopecia is the most common cause of hair loss in adults, but many other causes of hair loss have been identified. Non-scarring causes, in which hair is lost temporarily or permanently but the scalp is left intact, and Scarring causes, in which the condition that causes hair loss also causes injury and scarring of the scalp.
Because injury and subsequent scarring can destroy hair follicles, scarring alopecia is more likely to result in permanent hair loss. While it is easy to recognize when hair is being lost, it can be difficult to discover the cause. Some hair loss is due to skin conditions that are recognizable only by a medical specialist. Unexplained hair loss always warrants medical consultation. Hair loss can be a symptom-even an initial symptom-of underlying disease involving the endocrine system (pituitary, thyroid, adrenal glands), digestive system (intestines, liver), urinary tract (kidneys) or skin. Unexplained hair loss should be pursued by medical examination.