Is prenatal testosterone‐estrogen balance associated with psoriasis?

The etiopathogenesis of psoriasis is not understood; however, psoriasis is affected by hormones, particularly the sex steroids. The second-to-fourth digit (2D:4D) ratio, which is an indicator of prenatal sex hormone balance, has been studied in various diseases that are affected by hormones. A total of 369 individuals comprising 172 patients with psoriasis and 197 healthy volunteers were included in the study. Patients with psoriasis were divided into type-1 and type-2, according to age of onset and family history. The 2D:4D ratio of both hands was recorded for all participants. Females in the psoriasis group had a lower 2D:4D ratio in both hands compared with those in the control group, with no significant difference. Males in the psoriasis group had a higher 2D:4D ratio for both hands compared with those in the control group (P = .009 and P < .001 for the right and left hands, respectively). Further, male patients with type-1 psoriasis had a lower 2D:4D ratio compared to those with type-2 psoriasis. Our results suggest that an alteration of the estrogen-testosterone balance due to prenatal testosterone activity is an independent predisposing factor for psoriasis in males.