Phil B.FontanarosaMD, Deputy EditorStephen J.LurieMD, PhD, Fishbein Fellow
To the Editor: Dr Mills and colleagues1 reported a significantly lower excretion of the major urinary metabolite of 2,3 dinor-6-keto PGF1α (PGI-M) in women who developed preeclampsia compared with matched normotensive control subjects. These differences were detectable by 13 to 21 weeks of gestation.
In a longitudinal study of the urinary excretion of metabolites of the vasoactive prostanoids 6-keto PGF1α, and PGI2, and TxA2, TxB2, and 2,3 dinor TxB2 performed in early twin and singleton pregnancies resulting from in vitro fertilization and embryo transfer, we found significant increases in the excretion of PGI2 metabolites as early as 40 days after embryo transfer.2,3 The excretion of PGI2 metabolites continued to increase during the first half of gestation. Concentrations of TxB2 were low and showed virtually no increase in the first 20 weeks of pregnancy. This resulted in a significant elevation of the PGI2-to-TxA2 ratio with advancing gestation. In twin pregnancies, increases in the excretion of PGI2 metabolites were more pronounced than in singleton pregnancies.2,3 These findings were confirmed by Moutquin et al,4 who also found increased PGI2 production from 10 weeks until term in pregnancies with chronic hypertension. The increased PGI2 production in chronic hypertension, contrary to the reduced PGI2 production reported by Mills et al in the (acute) preeclamptic state, might reflect a compensatory mechanism aimed at facilitating vasodilatation in the renal and systemic circulation. In all studies,1- 3 the urinary excretion of the 2,3-dinor metabolites of PGI2 and TxA2 was determined. The excretion of these prostanoid metabolites provides a reasonable representation of in vivo production and can be used for comparative studies on the balance between PGI2 and TxA2 during gestation.3
van der Weiden RMF, Helmerhorst FM. Prostacyclin and Thromboxane and the Development of Preeclampsia. JAMA. 2000;283(12):1568. doi:10.1001/jama.283.12.1568-JLT0322-16-1