Endocrine Abstracts

Background: Little is known about the possible deleterious effects of phthalate exposure on endogenous sex steroid levels in children

Design: A longitudinal study.

Materials and methods: 168 Healthy children (84 girls) were examined every 6 months for 5 years, with pubertal staging, measurements of serum levels of DHEAS and Δ4-androstenedione (Adione) and repetitive longitudinal morning urinary measurements of 14 phthalate metabolites, corresponding to seven different phthalate diesters.

A geometric mean (GM) excretion of each child was calculated as the GM urinary phthalate amount (ng) per kilogram (kg) body weight in consecutive urine samples.

Results: We found that girls with excretion of the sum of dibutyl phthalate isomers (MBP) and di(2-ethylhexyl) phthalate (DEHP) metabolites above geometric group mean (795 and 730 ng/kg respectively) had lower serum levels of DHEAS and Adione, although only statistical significant at 13 years of age. In boys we found that excretion of MBzP above geometric group mean (346 ng/kg) was associated with a lower serum level of DHEAS at 11 years of age. A lower age at pubarche was observed in the boys with ‘high’ excretion of the sum of dibutyl phthalate isomers (MBP) metabolites (11.0 vs 12.3 years).

Conclusion: We provided some evidence that excretions of the phthalates, MBP in girls and MBzP in boys, were negatively associated with adrenal androgen levels. However, the lower androgen levels were not correlated to changes in age at pubarche.

The lower androgen levels in girls in the ‘high’ excretion group of MBP did not appear to influence onset of puberty. However, the boys in the ‘high’ excretion groups of MBP and the molar sum of correlated phthalates appeared to start puberty earlier than the boys in the ‘low’ excretion group. Our study did not reveal any clues with regard to possible mechanisms, but we speculate that theoretically, phthalates may not just interfere with steroidogenesis but they could also act directly at the hypothalamic-pituitary level.