Foetal Exposure to Phthalates and Endocrine Effects on the Leydig Cell

Abstract

This review examines the association between early life exposure to phthalates in human males and Leydig cell endocrine function. A systematic search was performed in PubMed and EMBASE, identifying 17 studies for analysis. Association scores weighted for number of phthalates and subjects were calculated for luteinizing hormone (LH), testosterone, testosterone/LH ratio and insulin-like factor 3 (INSL3). The scores ranges from full consistency of positive (score = 1), through inconsistent (score = 0), to negative/inverse (score = −1) associations. LH and early life phthalate exposure showed a statistically significant weighted phthalate association score of 0.18. Testosterone showed largely null results, whereas testosterone/LH ratio showed a negative association, both not statistically significant. A rise in LH, and decrease of testosterone/LH ratio, indicates that early life phthalate exposure results in a demand for a larger LH stimulus to produce the same amount of testosterone, and perhaps a decreased function of the Leydig cells, that manifests with the onset of high testosterone production in puberty and adulthood. A statistically non-significant decrease in INSL3 with a weighted phthalate association score of −0.29 supports this finding. An early life phthalate exposure-induced decline in Leydig cell function could possibly impact the spermatogenesis and adult male fertility.