Contents lists available at ScienceDirect Early Human Development journal homepage: www.elsevier.com/locate/earlhumdev Second to fourth digit ratio (2D:4D) in women with carpal tunnel syndrome ☆ Anna Kasielska-Trojan a, ⁎ , Aneta Sitek b , Bogusław Antoszewski a a Plastic, Reconstructive and Aesthetic Surgery Clinic, Medical University of Łódź, Poland b Department of Anthropology, University of Łódź, Poland ARTICLEINFO Keywords: Carpal tunnel syndrome Digit ratio Waist-hip ratio ABSTRACT Background: Carpal tunnel syndrome (CTS), a median nerve compressive neuropathy at the wrist, is the most common entrapment nerve disorder. Sex is an important risk factor of CTS as this condition is to five times more commoninwomenthaninmen(sex-hormonedependent).Therearenostudiesconcerning2D:4D(biomarkerof prenatal sex steroids exposure) in patients with CTS. Aim: Here we consider the relationship between 2D:4D and CTS in women. Study design and methods: The study involved 90 female participants (40 with a severe CTS (the mean age - 52.78yrs.,SD11.44)and50controlwomen(themeanage-47.2yrs.,SD8.23)).Anthropometricmeasurements were performed and the following indices were calculated: BMI, WHR and right and left 2D:4D. Results: AstepwiselogisticregressionmodelshowedthathigherWHRandlowerright2D:4Dincreasetheriskof CTS in women (AUC=0.8865). Conclusions: These associations may suggest a role for prenatal and post-natal sex-hormones in CTS develop- ment, i.e. in the context of oestrogen receptor activation (number and/or sensitivity) and the pattern of fat distribution. Further studies examining the role of hormonal influence in this disorder may help to plan pro- phylaxis of CTS (e.g. early HRT). 1. Introduction Carpal tunnel syndrome (CTS), a median nerve compressive neu- ropathy at the wrist, is the most common entrapment nerve disorder. It iscausedbyanincreasedpressurewithinthecarpaltunnel,whichleads toclinicalsymptomsinthehand(paraesthesia,numbnessandweakness due to muscle atrophy), followed by damage to the median nerve. CTS affects approximately 3.8% of general population [1,2]. The risk factors for CTS include: age, sex, diabetes, hypothyroidism, obesity, tobacco use, hand injury, pregnancy and occupational risk factors - repetitive wrist motions, repetitive microtrauma [3–8]. How- ever, a specific etiological factor may not be detected in about 50% of patients with CTS. These idiopathic forms may be related to individual changes in hand anatomical features, such as a size of a hand and wrist [9,10]. Sex is an important risk factor of CTS as this condition is three to five times more common in women than in men [11]. It was suggested that this may be associated with increased expression of oestrogen re- ceptor alpha and beta (ERα and ERβ) in the tenosynovial tissues of postmenopausal women with CTS [12]. However, this observation was not confirmed by Toesca et al. who found no statistically significant difference between male and female groups in the number of oestrogen and progesterone (PR) positive cells within transverse carpal ligaments (TCL) or synovial tissue of CTS patients [13]. Similarly, Mohammadi et al. showed that ER expression in TCL and serum oestrogen levels were not significantly different in women with CTS compared to the control women [14]. Patterns of relative finger-force across the digits may be influenced by prenatal sex steroids. For example, individuals who score high for autism spectrum disorder, a trait associated with high prenatal androgen and low prenatal oestrogen, tended to favour the use of the 4th digit in a multi-digit force-producing task [15]. Therefore, CTS development may be influenced by both prenatal and adult sex steroids. The relative lengths of the second digit and fourth digit (digit ratio: 2D:4D)isasexuallydimorphictraitinhumans.Manningsuggestedthat 2D:4D is a biomarker of prenatal sex steroids exposure - low 2D:4D correlates with high prenatal testosterone and low oestrogens, while high 2D:4D results from low foetal testosterone and high oestrogens https://doi.org/10.1016/j.earlhumdev.2019.104829 Received 4 June 2019; Received in revised form 21 July 2019; Accepted 23 July 2019 ☆ This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. ⁎ Corresponding author at: Plastic, Reconstructive and Aesthetic Surgery Clinic, Medical University of Lodz, Kopcinskiego 22, Lodz 90-153, Poland. E-mail address: annakas@toya.net.pl (A. Kasielska-Trojan). Early Human Development 137 (2019) 104829 0378-3782/ © 2019 Published by Elsevier B.V. T