Digit ratio (2D:4D) does not correlate with daily 17β-estradiol and progesterone concentrations in healthy women of reproductive age.

Abstract

Second-to-fourth digit ratio (2D:4D) is proposed as a proxy for the prenatal balance of sex hormones, is related to hormone-dependent characteristics in adult life, and is a possible predictor of disease later in life. Here, we studied the relationship between 2D:4D and ovarian steroid hormones (17β-estradiol and progesterone) among women of reproductive age. From 186 healthy premenopausal women, aged 24-37 years, we collected saliva samples daily during the entire menstrual cycle. Data on reproductive and lifestyle characteristics were collected via questionnaires, and anthropometric measurements were performed. No statistically significant relationships were detected between adult women's sex hormone concentrations (17β-estradiol and progesterone) during the menstrual cycle and 2D:4D, in either left or right hand, when controlling for size at birth, body mass index, and physical activity. This study shows, for the first time in a large sample of women of reproductive age, that 2D:4D is not a predictor of adult women's sex hormone concentration. The lack of relationship may be because 2D:4D might be genetically determined and is not related to maternal nutritional environment during fetal development. These results support the hypothesis that, in contrast to the nutritional quality of the fetal environment, the fetal hormonal environment (reflected by 2D:4D) does not determine reproductive physiology in later life.