Hair Diameter in Female Baldness

In a 1972 study involving 131 Caucasian women, researchers found that hair diameter decreased with age in those experiencing diffuse hair thinning. The study consisted of 58 women with diffuse thinning—44 without endocrine abnormalities and 14 with hypothyroidism—and a control group of 73 women with normal hair. Measurements of 20 scalp hairs from each participant showed that the mean hair diameter was significantly lower in women with thinning than in controls of the same age. Women with normal hair had a symmetrical distribution of hair diameters with a peak at 0.08 mm, while those with diffuse alopecia without endocrine abnormalities had a wider spread with peaks at 0.04 mm and 0.06 mm. The hypothyroid group had a similar distribution but with more thinner hairs. These findings suggest that hair follicles may not all respond the same way in the development of diffuse thinning and that there could be multiple types of follicles on the human scalp. Cases of alopecia areata and post-partum or post-febrile hair thinning were not included in the study.