Sonographic comparison of subcutaneous fat layer thickness in the scalp area in patients with androgenetic alopecia compared to healthy individuals: Cross-sectional.

Introduction: Androgenetic alopecia (AGA) is one of the most common alopecia among men and women worldwide. It is a nonscarring alopecia that has a characterized pattern. In female pattern AGA, the hairline is stable but general thinning occurs most notably in the frontal region. In male-pattern AGA, the hairline is receding and the thinning is most notable in the frontotemporal region. AGA has a complex pathogenesis and relation of subcutaneous fat in the scalp region and the miniaturization of terminal hair follicles is vague. In this study, subcutaneous fat in the frontal scalp an important region for AGA is compared to the occipital scalp that is spared in AGA.

Method: Our study is a cross-sectional study that has four groups. Male patient, female patient, male control, female control. Every group has 15 individuals. All of the people in the study are those referred to Rasoul Akram's dermatology clinic. The severity of alopecia is classified by Norwood scaling for male pattern AGA and Ludwig scaling for female pattern AGA. Subcutaneous tissue in the frontal and occipital regions is measured by ultrasonography. For evaluating the effect of aging on subcutaneous fat thickness, we subdivided any group into more than 40 years old and between 20 and 40 years old and compared these two subgroups.

Results: The mean age of the three groups of male patient, female patient, and female control is 40 y/o and the mean age of male control is 41 y/o. The mean subcutaneous fat layer thickness in frontal region in male patients group is 6.0 mm (more than 40 y/o = 6.6 mm, between 20 and 40 y/o = 5.5 mm), in female patients group 5.1 mm (more than 40 y/o = 5.7 mm, between 20 and 40 y/o = 4.6 mm), in the male control group is 4.4 mm (more than 40 y/o = 4.7 mm, between 20 and 40 y/o = 4 mm) and in the female control group is 4.1 mm (more than 40 y/o = 4.5 mm, between 20 and 40 y/o = 3.6 mm). The mean subcutaneous fat layer thickness in the occipital region in the male patient's group is 6.4 mm (more than 40 y/o = 6.7 mm, between 20 and 40 y/o = 6 mm), in the female patient's group 6.1 mm (more than 40 y/o = 6.5 mm, between 20 and 40 y/o = 5.7 mm), in the male control group is 6.3 mm (more than 40 y/o = 6.8 mm, between 20 and 40 y/o = 5.7 mm) and in the female control group is 6.2 mm (more than 40 y/o = 6.6 mm, between 20 and 40 y/o = 5.8 mm).

Conclusion: This study demonstrates that the subcutaneous fat layer in the frontal region in both males and females is thicker in AGA patients than healthy group and the more severe the AGA, the thicker is subcutaneous layer in the frontal region. In the male patients group, the subcutaneous fat layer in the frontal region is thicker than in the female patients group but in the male and female control groups is not so different. The subcutaneous fat layer in the occipital region is thicker in older individuals in both patients and control groups but is not different when compared to AGA patients and control individuals.