Association of a Chronic Stress Biomarker With Advanced Development of Breast and Testicular Volume

The actual biologic pathways linking early childhood adversity to pubertal development are difficult to uncover.¹ Daily, chronic activation of the hypothalamic-pituitary-adrenal axis might be one of the possible mechanisms, which unfolds slowly over months and years compared with the less-frequently deployed acute stress response.

Hair cortisol concentration (HCC), representative of chronic stress over several months, would elucidate this finding.² It is increasingly used as a biological marker of chronic stress.³ Virtually all attempts to link adversity with male pubertal development have proven unsuccessful.⁴ This study examines the correlation of HCC with testicular volume and breast development among boys and girls aged 6 to 9 years old.

Participants were recruited directly in grades 1 through 3 from 3 large elementary schools of Bengbu, Anhui Province, China, in March 2016. The final sample of children who had available hair cortisol and puberty data consisted of 1263 children (598 boys and 665 girls). Children were a mean (SD) age of 8.01 (0.8) years (range, 6.4-9.9 years). We secured approval from the institutional review board at Anhui Medical University and then obtained written informed consent from parents and school teachers as well as child assent.

Hair samples were minced by hand using small surgical scissors. Wash and steroid extraction procedures followed the protocol described by Veldhorst et al.⁵ A commercially available enzyme-linked immunosorbent assay kit for salivary cortisol was used to measure cortisol concentrations.

Breast Tanner stage was assessed by the same female pediatric endocrinologist. Cutoff points of early breast onset are 8.0 years and 9.8 years for Tanner stages II and III, respectively.⁶ Testicular volume was estimated by using Prader orchidometer.

The cortisol concentrations are presented by their median and interquartile range. Multivariable logistic regression analyses and linear regression were used to test for association between HCC and pubertal onset.

The median cortisol concentration in scalp hair was 11.82 pg/mg. There was no difference in cortisol levels with respect to sex (boys, 11.87 pg/mg and girls, 11.75 pg/mg).

As Table 1 illustrates, early breast development was found to be significantly higher in the third quartile (n = 51 [35.7%]) and fourth quartile (n = 57 [40.7%]) of hair cortisol concentration compared with the lowest quartile (n = 25 [16.9%]). The multivariable-adjusted odds ratios for early breast development were 2.190 (95% CI, 1.160-4.133) and 2.497 (95% CI, 1.318-4.730) in girls with the highest HCC quartiles (third and fourth), respectively, compared with the lowest quartile of HCC.

Table 2 shows that among boys, there was a dose-response–like increase in testicular volume by quartiles of HCC. When adjusting for age, socioeconomic status, and body mass index, HCC was still significantly correlated with advanced testicular volume (HCC quartiles: B,  0.12; 95% CI, 0.07-0.17; β = 0.183; P < .001; continuous measure of HCC: B, 0.057; 95% CI, 0.029-0.086; β = 0.166; P < .001).

This study investigated the association between a biomarker of chronic stress (HCC) and breast onset and testicular volume among 1263 children during pubertal transition period. As hypothesized, we found a 2.5-fold increased risk of early breast onset in girls in the highest quartile of HCC compared with girls in the lowest quartile and an increase of 0.12 mL in testicular volume with each quartile increase in HCC among boys. More than one-third of girls with the highest quartiles of HCC showed more advanced breast development.

To our knowledge, this is the first study to have measured the cortisol level in hair in children around pubertal transition. The work holds the promise to further illuminate the determinants of pubertal timing, perhaps even one mechanism by which it mediates effects of contextual adversity. Further research of a longitudinal nature is needed to determine the causal relationship, especially among boys.

This study revealed dose-response–like relations between HCC and advanced pubertal development in boys and girls. Hair cortisol has significant potential to shed light on stress and pubertal development.

Corresponding Author: Ying Sun, MD, Department of Maternal, Child and Adolescent Health, School of Public Health, Anhui Medical University, 81 Meishan Road, Hefei, Anhui Province 230032, China (sy54@yeah.net).

Accepted for Publication: January 10, 2017.

Published Online: April 17, 2017. doi:10.1001/jamapediatrics.2017.0038

Author Contributions: Dr Sun had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Sun, Tao.

Acquisition, analysis, or interpretation of data: Sun, Xu, Hu.

Drafting of the manuscript: Sun, Hu.

Critical revision of the manuscript for important intellectual content: Sun, Xu, Tao.

Statistical analysis: Sun, Hu.

Obtained funding: Sun, Xu.

Administrative, technical, or material support: Xu, Tao.

Supervision: Tao.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was funded by grants 81673188 and 81302449 from the National Natural Science Foundation of China (Drs Sun and Xu), grant KJ2016A338 Key Project of Natural Science Foundation of Anhui Education (Dr Sun), and the Faculty Doctoral Fellowship of Anhui Medical University.

Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: Ya-ping Lai, MS, and Jiao Fang, MS, School of Public Health, Anhui Medical University, assisted with data collection. No compensation was received from a funding sponsor for these contributions.