Evaluation of glyphosate exposure on testosterone among U.S. adult men

ABSTRACT

Glyphosate is one of the most commonly used herbicide globally. It is considered an endocrine-disrupting chemical (EDC) that can affect the production and function of various hormones including testosterone. Testosterone is an important sex hormone in men that governs sexual development, function, metabolism, and reproduction. Glyphosate has been associated with testosterone impairment in a number of experimental studies; however, the association between glyphosate exposure and testosterone among U.S. adult men in the general population is currently unknown. Data was leveraged from the National Health and Nutrition Examination Survey (NHANES), which is an annually conducted, population-based cross-sectional study. Urinary levels of glyphosate were quantified as measures of exposure. Total testosterone was quantified from the serum of adult men ages 18+, and a serum value of <300 ng/dL was used to define low testosterone. Chi-square, analysis of variance (ANOVA), and multivariable, weighted linear and logistic regression analyses were used to compare sociodemographic and biological characteristics between quartiles of glyphosate exposure, identify risk factors for glyphosate exposure and low testosterone, and to analyze the relationship between glyphosate and testosterone. A total of 441 adults were included in final analyses, representing 18,345,154 individuals after survey weighting. The geometric mean of glyphosate was 0.58 ng/mL (IQR: 0.26–0.66). Race/ethnicity was significantly associated with glyphosate exposure, where white men had higher mean glyphosate exposure compared to black men (β = 0.11, p = .04). Analysis of total glyphosate modeled as a continuous variable was not significantly associated with testosterone (β = 10.93, p = .75). Similarly, no significant associations were observed when categorizing urinary glyphosate into quartiles when evaluating continuous testosterone (β = 3.46 p = .85, β = −6.74 p = .78, β = 10.22 p = .75 for quartiles 2–4, respectively), and categorical testosterone (i.e. normal/low) (OR = 2.29 95% CI [0.61,8.58], OR = 0.88 95% CI [0.18,4.08], OR = 1.14 95% CI [0.39,3.30]) for quartiles 2–4, respectively. We present the first evaluation of population-based urinary glyphosate levels on testosterone among U.S. adult men. We observed no significant associations between glyphosate and testosterone levels. Future studies are warranted to corroborate these findings, and to test these associations in prospective studies and within populations exposed to high levels of glyphosate.

KEYWORDS:

• glyphosate
• testosterone
• herbicides
• endocrine disruption

Authors’ contributions

Frank Glover is the primary author who drafted the manuscript, obtained references, performed most of the data analysis, and helped with the conceptualization of the study. Federico Belladelli and Francesco Del Giudice both performed data analysis with the regression models, obtained background information for references, and proof read the manuscript drafts. Dana Barr, Jasmin Eatman, Wade Muncey, and Nicolas Seranio also performed extensive background research, as well as proofed all drafts of the manuscript and helped created figures and tables. Dr. Eisenberg provided guidance at the conceptualization stage, proofed all drafts of the manuscript, and helped perform regression analysis.

Ethics approval and consent to participate

Health information collected in the NHANES is kept in strictest confidence. During the informed consent process, survey participants were assured that data collected will be used only for stated purposes and will not be disclosed or released to others without the consent of the individual or the establishment in accordance with Section 308(d) of the Public Health Service Act (42 U.S.C. 242 m).

Consent for publication

Participants in this study agreed to consent for publication in accordance with Section 308(d) of the Public Health Service Act (42 U.S.C. 242 m).

Disclosure statement

The authors have no competing financial interests.

Data availability statement

A full list of data sets supporting the results in this research article can be found at: https://wwwn.cdc.gov/nchs/nhanes/continuousnhanes/default.aspx?BeginYear=2013.

Additional information

Funding

The authors received no external funding for this research study.