Levothyroxine Treatment During Pregnancy: A Metabolomics Study

ABSTRACT Levothyroxine is one of the most prescribed drugs during pregnancy. Our aim was to determine levothyroxine treatment‐associated changes in the metabolite profiles and link these to the health of the newborn. Metabolite profiles of 118 levothyroxine‐treated and 118 healthy control pregnancies were determined with nuclear magnetic resonance‐based metabolomics from (1) umbilical cord blood samples, (2) samples collected during the first trimester and (3) during delivery from the pregnant women. There was a modest negative correlation between cord blood thyroid stimulating hormone (CBTSH) concentrations and Apgar scores at the 1 and 5 min time points in levothyroxine‐treated pregnancies. Furthermore, the concentrations of cord serum metabolites linked with anaerobic glycolysis, for example, lactate, citrate and glycerol, as well as all measured amino acids were negatively associated with Apgar scores. Moreover, cord serum concentrations of lactate, glycerol and alanine were modestly correlated with CBTSH concentrations in the levothyroxine‐treated pregnancies. In the during delivery samples, there was small but significant decrease in cholesteryl esters, cholesterol and phospholipids in small very low‐density lipoprotein in the levothyroxine‐treated pregnancies. In conclusion, levothyroxine treatment during pregnancy was associated with relatively small alterations in the blood metabolite profiles during pregnancy and labour.