Research
Anogenital distance in human male and female newborns: a descriptive, cross-sectional study
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* Corresponding author: Matthew P Longnecker longnecker@niehs.nih.gov
1 National Institute of Public Health, Av. Universidad 655, Col. Santa Ma. Ahuacatitlan, 62508 Cuernavaca, Morelos, Mexico
2 Mexican Institute of Social Security, Boulevard Benito Juarez #18 Tercer piso Col. Centro, C.P. 62000, Cuernavaca, Morelos, Mexico
3 National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, MD A3-05, PO Box 12233, Research Triangle Park, North Carolina 27709, USA
Environmental Health: A Global Access Science Source 2004, 3:8 doi:10.1186/1476-069X-3-8
Published: 13 September 2004Abstract
Background
In animal studies of the effects of hormonally active agents, measurement of anogenital distance (AGD) is now routine, and serves as a bioassay of fetal androgen action. Although measurement of AGD in humans has been discussed in the literature, to our knowledge it has been measured formally in only two descriptive studies of females. Because AGD has been an easy-to-measure, sensitive outcome in animals studies, we developed and implemented an anthropometric protocol for measurement of AGD in human males as well as females.
Methods
We first evaluated the reliability of the AGD measures in 20 subjects. Then measurements were taken on an additional 87 newborns (42 females, 45 males). All subjects were from Morelos, Mexico.
Results
The reliability (Pearson r) of the AGD measure was, for females 0.50, and for males, 0.64. The between-subject variation in AGD, however, was much greater than the variation due to measurement error. The AGD measure was about two-fold greater in males (mean, 22 mm) than in females (mean, 11 mm), and there was little overlap in the distributions for males and females.
Conclusion
The sexual dimorphism of AGD in humans comprises prima facie evidence that this outcome may respond to in utero exposure to hormonally active agents.