Abstract
Measurement of endogenous hormones in early life is important to investigate the effects of hormonally active environmental compounds. To assess the possible hormonal effects of different feeding regimens in different sample matrices of infants, 166 infants were enrolled from two U.S hospitals between 2006 and 2009. The children were classified into exclusive soy formula, cow milk formula or breast milk regimens. Urine, saliva and blood samples were collected over the first 12 months of life. Estradiol, estrone, testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and sex hormone-binding globulin (SHBG) levels were measured in the three matrices. Lower estradiol and LH levels were found in urine and saliva samples of soy formula-fed boys compared to cow formula-fed boys. Higher LH level was found in urine samples of soy formula-fed girls compared to cow formula-fed girls. However, we found neither a neonatal testosterone rise in the boys nor a gender-specific difference in testosterone levels, which suggests that urinary testosterone levels may not accurately reflect blood levels during mini-puberty. Nevertheless, our study shows that blood, urine and saliva samples are readily collectible and suitable for multi-hormone analyses in children and allow examination of hypotheses concerning endocrine effects from dietary compounds.
Highlights
Taken from dairy cows during pregnancy, the quantity of estrogens in various kinds of milk is too low to demonstrate biological activity[16]
Statistically significant difference in analytes’ concentrations between feeding regimens was found neither in boys nor in girls, except for lower estradiol level in soy formula-fed boys than in cow formula-fed boys found in both urine and saliva samples (12.60 vs 17.89 pg/mL, p = 0.013 and 13.90 vs 19.66 pg/mL; p = 0.008, respectively), lower luteinizing hormone (LH) level in soy formula-fed boys than in cow formula-fed boys found in both urine and saliva samples (0.32 vs 0.55 mIU/mL, p = 0.025 and 0.57 vs 0.85 mIU/mL, p = 0.033, respectively), and higher LH level in soy formula-fed girls than in cow formula-fed girls (0.62 vs 0.36 mIU/mL; p = 0.006) found only in urine samples (Table 1)
The intra- and inter-assay coefficients of variations (CVs) of all analytes for all matrices are less than 5%
Summary
Taken from dairy cows during pregnancy, the quantity of estrogens in various kinds of milk is too low (usually less than 10 pg/ml) to demonstrate biological activity[16]. Those given soy formula did not differ from those given cow milk based formula on their answers to general questions about health and reproduction. The result was criticized, because it did not measure hormone levels or reproductive function of individuals directly[18]. It may not reflect concentrations at the site of action, urine concentrations were usually conveniently collected from infants for hormone data. In a partly cross-sectional, partly longitudinal study to investigate possible hormonal effects for different infant feeding regimens, we collected urine, saliva, and blood from infants of different ages from birth to 1 year, and measured sex hormones, gonadotropins, and SHBG. This study was designed to develop methods, assess feasibility, and give information on the time course of the hormones and the correlation structure from the different sample matrices collected in infants
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