Abstract:
Background Infants' exposure to environmental endocrine disruptors has raised great concern. But due to the limits of sampling techniques, it is difficult to measure the hormone levels of infants in large cohort studies.
Objective The study is designed to determine whether the urine collected by disposable diapers can be used to measure the concentrations of 17β-estradiol (E2), testosterone (T), folliclestimulating hormone (FSH), and luteinizing hormone (LH) in urine of infants, and to establish a basis for the assessment of environmental endocrine disruptor exposure in early postnatal period.
Methods The urine with different spike levels of hormones (E2:146, 219, 292, 365, 438, 584, and 730 pmol/L; T:0.35, 0.7, 1.05, 1.4, 1.75, 2.1, and 2.8 nmol/L; FSH and LH:0.2, 0.4, 0.6, 0.8, 1.0, 1.2, and 1.6IU/L) were poured into dry disposable diapers of a selected brand and absorbed completely. After the absorbed urine was collected with CaCl2 powder, the concentrations of four hormones in urine were measured with Beckman Coulter UniCelTM DxI 800 Access Immunoassay System, and the accuracy and precisions of the results were calculated. The stability of the four hormones at different levels (E2:1 605.9, 2 049.9, and 2732.9pmol/L; T:1.79, 2.50, and 3.20nmol/L; FSH:0.78, 1.00, and 1.47 IU/L; LH:0.47, 0.61, and 0.83IU/L) after different storage periods (0, 30, and 100 d) at -20℃ was also investigated by calculating the relative standard deviations (RSD). Wet disposable diaper samples were collected at different ages (at birth, 14d, 28d, 42d, 3 months, and 6 months) of 15 infants (eight male infants and seven female infants) who were selected randomly from a cohort study implemented earlier in Daishan, Zhejiang Province, and were analyzed for the four hormones by the established method for preliminary verification.
Results E2 (146-730pmol/L), T (0.35-2.8nmol/L), FSH (0.2-1.6IU/L), and LH (0.2-1.6IU/L) in standard urine and the urine collected from wet disposable diapers all showed good linearity with determination coefficients (R2) of 0.956, 0.979, 0.997, and 0.991, respectively. The average recoveries of the four kinds of hormones at different spike levels were 95.4%, 98.3%, 69.7%, and 39.3%, respectively, with RSDs between 5.5%-21.6%. The RSDs were between 7.7%-31.0% of the four hormones stored at -20℃ over different periods. The concentrations of E2, T, FSH, and LH of 15 infants were between ND-44178pmol/L, ND-44.37nmol/L, ND-11.64IU/L, and ND-8.88IU/L, respectively.
Conclusion This method can be used to measure the concentrations of E2, T, FSH, and LH in urine of infants in early postnatal period, and may be applied to studies on the endocrine disrupting effects in infants exposed to environmental endocrine disruptors.
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