Female pattern baldness is a common clinical entity in women. It is characterized by a progressive decline in scalp hair density. In medical terms it is known as female androgenetic alopecia, suggesting that it may be perceived as the female equivalent of male androgenetic alopecia.
Clinical presentation of female pattern baldness
Hair loss may ensue at any age after the onset of adrenarche, which refers to the maturational surge in adrenal androgen production. Thus it may happen before pubarche, that is, the development of pubic hair, or preceding menarche, which refers to the first menstrual period. Prior to any visible reduction in hair volume, female pattern baldness may present with episodic or continuous hair shedding, or the diffuse thinning of hair over the crown.
In any case, the hallmark is a characteristic and recognizable pattern of the hair loss. Women tend to develop diffuse thinning over the mid-frontal scalp area, whereas the anterior hair-line is relatively spared. Such thinning is usually observed when the hair in the midline is parted, which often reveals a pattern that resembles a Christmas tree.
Hence female pattern hair loss has a different clinical presentation in comparison with the more easily recognizable male pattern baldness. The latter most often starts with a receding frontal hairline that advances to a bald patch on the top of the head. Unless there is an excessive production of androgens, it is quite uncommon for women to develop baldness according to the male pattern of hair loss.
Establishing a diagnosis
The diagnosis of female pattern hair loss is mainly clinical. Dermatoscopy can be employed as a useful tool for early detection. It also helps to differentiate it from other hair disorders that may also result in hair thinning. The hair pull test (a maneuver where tufts of hair along the scalp are gently pulled) is usually positive as miniaturization leads to shortened hair cycles with increased shedding.
Sophisticated diagnostic criteria based on trichoscopy (orscalp dermatoscopy) were proposed by Rakowska and her colleagues for the diagnosis of female pattern baldness. Major criteria include:
- more than four empty follicles in four images (using 70-fold magnification) taken in the frontal area
- more than 10% of hairs in the frontal region are thinner than 0.03 mm in diameter
- there is a lower average hair thickness in the frontal area when compared to the occipital region
Minor criteria in the same diagnostic compendium include:
- vellus hairs
- peripilar signs
- increased frontal to occipital ratio of single-hair pilosebaceous units
If two major criteria, or one major and two minor criteria, are fulfilled, there is 98% certainty that the correct diagnosis is female pattern baldness.
Scalp biopsy is often considered to be an indispensable tool in distinguishing between scarring and non-scarring forms of alopecia. Although this invasive procedure is usually not necessary to diagnose female pattern hair loss, it may be helpful if a definitive diagnosis cannot be established by clinical evaluation.
The trichogram represents a semi-invasive, plucking microscopic method where hair roots and hair cycles are appraised. It is useful as a complementary element which helps to confirm an early diagnosis of female pattern baldness by demonstrating inhomogeneous hair shafts. Recent studies have recommended dermatoscopy as a more useful approach, however.
Finally, laboratory tests are often pursued, with an emphasis on androgen levels testing during the follicular phase of the menstrual cycle. The results of these tests warrant further interdisciplinary assessments involving dermatologists, endocrinologists and gynecologists.