Investigation of the Association of the Second-to-Fourth Digit Ratio with Skin Sebum Levels in Females with Acne Vulgaris

A relationship between acne vulgaris (AV) and the masculinized (lower) second-to-fourth digit (2D:4D) ratio in females was demonstrated in our previous study. Development of the digits and the sebaceous glands both occur during the same gestational period; therefore, the association between the 2D:4D ratios and AV may result from the effects of the prenatal endocrine environment on the sebaceous glands. The aim of this study was to evaluate the relationship between the 2D:4D ratio and sebum levels in the skin of females with AV. In total, 215 female AV patients and 92 healthy controls, aged 18–35 years, were enrolled in this study. Finger-length measurements were made using a digital Vernier caliper, and the sebum levels of five facial areas were measured using a Sebumeter SM 815. Acne severity was assessed using the International Consensus Conference on Acne Classification System. The 2D:4D ratios of the AV patients were significantly lower than those of the controls, for both hands. The mean sebum levels in the T-zone, U-zone and whole face were significantly higher for AV patients compared with controls. The 2D:4D ratio in the left hand showed significant negative correlations with the sebum levels in the U-zone; however, no association was found between the 2D:4D ratios and sebum levels in the T-zone and whole face. While acne severity was positively correlated with skin sebum levels, no correlation between acne severity and 2D:4D ratios was observed. This study provides preliminary evidence regarding the association between lower 2D:4D ratios and higher rates of sebum secretion in the U-zone for females with AV. The 2D:4D ratio might be a predictor of sebum levels, as well as acne development, in females.