Prenatal masculinization of the auditory system in infants: The MIREC-ID study
- DOI
- Language of the publication
- English
- Date
- 2019-02-14
- Type
- Article
- Author(s)
- Nguyen,Tuong-Vi
- Jutras, Benoît
- Monnier, Patricia
- Muckle, Gina
- Velez, Maria
- Arbuckle, Tye E.
- Saint-Amour, Dave
- Publisher
- Elsevier
Abstract
Sex differences in inner-ear function are detectable in infants, notably through the measurement of otoacoustic emissions (OAEs). Prevailing theories posit that prenatal exposure to high levels of androgens in boys may weaken OAEs, and that this phenomenon may predominantly affect the right ear/left hemisphere (Geschwind-Galaburda (GG) hypothesis). Yet, actual tests of these models have been difficult to implement in humans. Here we examined the relationship between markers of fetal androgen exposure collected at birth (anogenital distances (AGD); penile length/width, areolar/scrotal/vulvar pigmentation) and at 6 months of age (2nd to 4th digit ratio (2D:4D)) with two types of OAEs, click-evoked OAEs (CEOAEs) and distortion-product OAEs (DPOAEs) (n = 49; 25 boys; 24 girls). We found that, in boys, scrotal pigmentation was inversely associated with the amplitude and reproducibility of CEOAEs in the right ear at 4 kHz, with trends also present in the same ear for mean CEOAE amplitude and CEOAE amplitude at 2 kHz. Penile length was inversely associated with the mean amplitude of DPOAEs in both the right and left ears, as well as with DPOAE amplitude in the right ear at 2 kHz and the reproducibility of CEOAEs in the left ear at 2.8 kHz. Finally, AGD-scrotum in boys was positively associated in boys with the amplitude of DPOAEs in the left ear at 2.8 kHz. Unexpectedly, there were no sex differences in the amplitude or reproducibility of OAEs, nor, in girls, any associations between androgenic markers and auditory function. Nonetheless, these findings, reported for the first time in a sample of human infants, support both the prenatal-androgen-exposure and GG models as explanations for the masculinization of auditory function in male infants.
Plain language summary
"Health Canada helps to protect the health of Canadians by assessing and managing the risks associated with exposure to endocrine disrupting chemicals. The endocrine hormones androgen and estrogen play important roles in the development of the child. Sex differences in hearing are detectable in infants. Prenatal exposure to high levels of androgens in boys may weaken hearing sensitivity and result in infant girls having better hearing. However, it has been difficult to measure prenatal exposure to androgens to test this theory. The goal of this study was to test the relationship between several markers of prenatal androgen exposure and measures of hearing function in infants. In the MIREC-ID Study, markers of androgen exposure (anogenital distance, penis length and width, skin pigmentation of genitals and the ratio of the 2nd and 4th fingers) were measured in infants. Measures of hearing were measured in 25 male and 24 female infants. The study found associations in boys between skin pigmentation of genitals and penis length with various measures of hearing function. No associations between any of the androgenic markers and auditory functions were found in girls. These findings, reported for the first time in a sample of human infants, suggest that prenatal androgen exposure is a possible explanation for why auditory (hearing) functions are different in male versus female infants. "
Subject
- Health,
- Health and safety