The diagnosis of androgenetic alopecia in men is generally straightforward. It is made by observing a “patterned” distribution of hair loss (see the previous session on Classification) and confirmed by observing the presence of miniaturized hair in the areas of thinning.

Miniaturization – the progressive decrease of the hair shaft’s diameter and length in response to androgens – can be observed using a densitometer, a hand-held instrument that magnifies a small area of the scalp where the hair has been clipped to about 1mm in length.

Dr. Bernstein Using the Electronic Hair Densitometer
Dr. Bernstein Using the Electronic Hair Densitometer

The photo, below left, was taken from a normal scalp. The follicular units (groups) are comprised of full-thickness, healthy terminal hair. Note the relatively uniform diameter of the hair shafts. The photo, below right, shows that many hairs have decreased in diameter (miniaturized). This is characteristic of androgenetic alopecia.

Dr. Bernstein Using the Electronic Hair Densitometer

The diagnosis of androgenetic alopecia is supported by a family history of hair loss, although a positive history is not always identified (see Genetics). In older patients, their own history of passing through the different Norwood stages is strongly suggestive of male pattern alopecia.

If the hair loss is diffuse (thin all over) rather than following one of the specific Norwood patterns, the diagnosis can be more difficult. However, the presence of miniaturization in the areas of thinning usually confirms the diagnosis of androgenetic alopecia. If the diagnosis is still unclear, a number of other conditions must be ruled out.

Medical conditions that can produce diffuse hair loss in men include thyroid disease and anemia. Certain medications, including some drugs used for high blood pressure and depression, and the use of anabolic steroids, can also cause male hair loss.

The following laboratory tests are often useful when a non-androgenetic cause for diffuse hair loss is suspected: blood chemistries, complete blood count, serum iron, thyroid functions, and tests for lupus and syphilis.

When the diagnosis of androgenetic alopecia is still uncertain, further diagnostic information can be obtained from a hair-pull test, a scraping and culture for fungus, a microscopic examination of the hair bulb and shaft, and a scalp biopsy. A dermatologic consultation is warranted whenever the cause of hair loss is unclear.

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