Renal handling of endogenous human chorionic gonadotrophin in preeclampsia

Objective: To test the hypothesis that the elevated maternal serum concentration of human chorionic gonadotrophin (hCG) in preeclampsia is due to altered renal handling of the hormone. Setting: Department of Obstetrics and Gynecology, Al Ain Hospital, United Arab Emirates, a tertiary center affiliated with the Faculty of Medicine and Health Sciences, UAE University. Methods: The renal clearances and handling of endogenous creatinine and human chorionic gonadotrophin were compared in 14 normotensive volunteer and 14 preeclamptic mothers who received oral hydration at 34-37 weeks' gestation. The hCG content in the placentas was estimated immunohistochemically after delivery. Results: Maternal serum concentration of hCG (p = 0.0057), the placental hCG immunopositive cell (p < 0.0001), and syncytial knot counts (p < 0.0001) were significantly higher in preeclamptic mothers. The renal clearances of endogenous creatinine and hCG and fractional hCG clearance were not significantly different in both groups. Significantly increased amounts of hCG were filtered (p = 0.007) and excreted (p = 0.007) by preeclamptic mothers. Only a small but fixed proportion of the filtered load of hCG is excreted in both groups and there was a positive correlation (r = 0.5, p = 0.005) between filtered and excreted loads of hCG. Conclusion: The results indicate increased placental content of hCG in preeclampsia. The resultant increased maternal serum concentration is probably sustained by the mechanism of renal handling of the hormone.