Finger ratio in chuvashian population: prevalences, sexual dimorphism and association with reproductive indices
In a Chuvashian sample (803 males and 738 females) we evaluated the mean values of 2D:4D ratio, putative bioassay for prenatal androgen exposure, the contributions of phalanges and metacarpals to the 2D:4D ratio, and the association between 2D:4D finger length ratios (representing the prenatal environment, i.e., early androgen exposure) and reproductive indices, such as age at menarche, menopausal age and length of reproductive period. Age, sex, anthropometric data and x-rays of both hands were collected. Each hand was visually classified on x-ray as either Type 1 - index finger was longer than ring finger; Type 2 - equal; or Type 3 - shorter than the ring finger. The following measurements (1) from the mid-point of the base of the proximal phalanx to the mid-point of the tip of the distal phalanx; and (2) from the mid-point of the base to the mid-point of the tip of the metacarpal were obtained from the index and ring fingers. Visual classification was significantly associated with the measured 2D:4D length ratio. Women had a higher prevalence of Type 1 and Type 2, but lower prevalence of Type 3 ratio in both hands. Men had lower measured 2D:4D phalangeal, metacarpal and ray (combined) ratios than women. We found that a low 2D:4D ratio (radiologically evaluated), a masculine 2D:4D ratio type (visually evaluated) were associated with a later menarche and a shorter reproductive period. No association was found with menopausal age.