Monocarboxylate transporter 8 expression in the human placenta: the effects of severe intrauterine growth restriction

Thyroid hormones (THs) are essential for normal fetal development, with even mild perturbation in maternal thyroid status in early pregnancy being associated with neurodevelopmental delay in children. Transplacental transfer of maternal THs is critical, with increasing evidence suggesting a role for 3,3',5-tri-iodothyronine (T3) in development and function of the placenta itself, as well as in development of the central nervous and other organ systems. Intrauterine growth restriction (IUGR) is associated with fetal hypothyroxinaemia, a factor that may contribute to neurodevelopmental delay. The recent description of monocarboxylate transporter 8 (MCT8) as a powerful and specific TH membrane transporter, and the association of MCT8 mutations with profound neurodevelopmental delay, led us to explore MCT8 expression in placenta. We describe the expression of MCT8 in normal human placenta throughout gestation, and in normal third-trimester placenta compared with that associated with IUGR using quantitative reverse transcriptase PCR. MCT8 mRNA was detected in placenta from early first trimester, with a significant increase with advancing gestation (P=0.007). In the early third trimester, MCT8 mRNA was increased in IUGR placenta compared with normal samples matched for gestational age (P