Digit ratio (2D:4D) and maxillary sinus volume: A link between prenatal sex steroids and a paranasal reservoir of nitric oxide?

Abstract

Background: The paranasal sinuses serve as a reservoir for nitric oxide (NO), a vasodilator associated with cardiovascular health and exercise performance. Digit ratio (2D:4D), a proxy for first trimester testosterone and estrogen, is also a correlate of cardiovascular health and exercise performance. There are sex differences in the volume of fractional exhaled NO (FeNO: males>females) and in mean 2D:4D (males<females). Here we consider the relationships between 2D:4D and the volume of the largest paranasal sinus, i.e. the maxillary sinus (MS), in men and women.

Methods: 30 male and 30 female participants, mean age of 38.4 ± 11.8 years, who had a paranasal sinus computer tomography (CT) scan were included. The MS volumes were calculated from the scans using GE software. The 2D:4D ratios were obtained from direct measurements of the 2nd and 4th digits.

Results: Sex differences were not significant in 2D:4D or MS volumes. In males, 2D:4D correlated negatively with right MS volume (right and left 2D:4D, r = -0.58) and left MS volume (right 2D:4D r = -0.45, left 2D:4D r = -0.40). After removal of the effects of age, BMI and digit length all correlations for the right MS remained significant as did that between right 2D:4D and left MS. There were no significant correlations in females.

Conclusion: We have found that low (androgenized) 2D:4D in men is associated with high MS volumes with stronger effects for the right MS. Our findings indicate that in men high prenatal testosterone relative to estrogen is related to high MS volume. We suggest that 2D:4D may be negatively related to FeNO volume produced by the MS.

Keywords: Digit ratio; FeNO production; Maxillary sinus volume.