Second to fourth digit ratio, adult testosterone level and testosterone deficiency

Abstract

The ratio of the second and fourth finger lengths (2D/4D) is related to intrauterine exposure to testosterone. The relationship between 2D/4D and adult hormonal pattern is controversial. The aim of our study was to determine if there was a relationship between adult serum testosterone levels and the 2D/4D ratio. We prospectively recruited 204 consecutive patients referred for transrectal prostate biopsy between January 2008 and June 2009. The same physician performed clinical examinations, 2D/4D measurements and the transrectal biopsy in all cases. Cut-off points of 231 and 346 ng/dL testosterone (8 and 12 nmol/L) were used. 2D/4D determination was done with a vernier calliper on the left hand. The hormonal profile (testosterone and sexual hormone binding globulin) of the patients was determined between 7.00 am and 11.00 am. Age, weight, height, body mass index, toxic habits, digital rectal examination, prostate-specific antigen and 2D and 4D measurements were recorded prospectively. The mean age was 67 ± 7 years and the mean testosterone level was 413 ± 18 ng/dL (14.33 ± 0.62 nmol/L). The percentages of patients with testosterone <231 ng/dL (8 nmol/L) and testosterone <346 ng/dL (12 nmol/L) were 6.1 and 30.6 respectively. Univariate analysis showed that low 2D/4D ratios were related to higher levels of testosterone (B=-741.98; β=-0.165, P= 0.045) and also with low prevalence of biochemical hypogonadism (testosterone <346 ng/dL). Mean 2D/4D ratio in patients with testosterone >346 ng/dL was lower than in patients with testosterone <346 ng/dL (2D/4D 0.97 ± 0.037 vs 0.99 ± 0.043 depending on their hormonal status, P= 0.05). High 2D/4D ratio was associated with low testosterone serum levels (P= 0.046). The 2D/4D ratio is related to adult testosterone levels and the presence of testosterone deficiency syndrome. Patients with high 2D/4D ratios have lower testosterone levels and higher risk of testosterone deficiency syndrome.