A disruption of the growing phase causes abnormal loss of anagen hairs (anagen effluvium). Diagnosis
Because they are not usually associated with an increased loss rate, male-pattern and female-pattern hair loss do not generally require testing. If hair loss occurs in a young man with no family history, drug use could be the cause. The pull test helps to evaluate diffuse scalp hair loss. Gentle traction is exerted on a group of hairs (about 40–60) on three different areas of the scalp. The number of extracted hairs is counted and examined under a microscope. Normally, fewer than three hairs per area should come out with each pull. If more than ten hairs are obtained, the pull test is considered positive. The pluck test is conducted by pulling hair out "by the roots". The root of the plucked hair is examined under a microscope to determine the phase of growth, and is used to diagnose a defect of telogen, anagen, or systemic disease. Telogen hairs have tiny bulbs without sheaths at their roots. Telogen effluvium shows an increased percentage of hairs upon examination. Anagen hairs have sheaths attached to their roots. Anagen effluvium shows a decrease in telogen-phase hairs and an increased number of broken hairs. Scalp biopsy is used when the diagnosis is unsure; a biopsy allows for differing between scarring and nonscarring forms. Hair samples are taken from areas of inflammation, usually around the border of the bald patch. Daily hair counts are normally done when the pull test is negative.
Pattern hair loss by age 50 affects about half of men and a quarter of women. About 2% of people develop alopecia areata at some point in time. Terminology
Baldness is the partial or complete lack of hair growth, and part of the wider topic of "hair thinning". The degree and pattern of baldness varies, but its most common cause is androgenic hair loss, alopecia androgenetica, or alopecia seborrheica, with the last term primarily used in Europe. Hypotrichosis
Hypotrichosis is a condition of abnormal hair patterns, predominantly loss or reduction. It occurs, most frequently, by the growth of vellus hair in areas of the body that normally produce terminal hair. Typically, the individuals hair growth is normal after birth, but shortly thereafter the hair is shed and replaced with sparse, abnormal hair growth. The new hair is typically fine, short and brittle, and may lack pigmentation. Baldness may be present by the time the subject is 25 years old. Signs and symptoms
Symptoms of hair loss include hair loss in patches usually in circular patterns, dandruff, skin lesions, and scarring. Alopecia areata (mild – medium level) usually shows in unusual hair loss areas, e.g., eyebrows, backside of the head or above the ears, areas the male pattern baldness usually does not affect. In male-pattern hair loss, loss and thinning begin at the temples and the crown and hair either thins out or falls out. Female-pattern hair loss occurs at the frontal and parietal. People have between 100,000 and 150,000 hairs on their head.