Calcitonin gene- and parathyroid hormone-related peptides in preeclampsia: Effects of magnesium sulfate

Objective: To determine whether circulating levels of calcitonin gene-related peptide (CGRP) and parathyroid hormone-related peptide (PTHrP) are altered in preeclampsia, and to assess the effects of magnesium sulfate therapy on circulating levels of these two peptides. Methods: The study population included 25 women with preeclampsia and 25 normotensive controls of similar gestational age. The effects of magnesium sulfate therapy were evaluated in 17 of the 25 preeclamptic women. Circulating levels of immunoreactive CGRP and PTHrP, including calcium, magnesium, and phosphate in the maternal and umbilical cord serum were measured. Results: The frequency of preeclampsia subjects with nondetectable PTHrP (under 3 pg/mL) was significantly higher (92% versus 48%, P < .001), whereas maternal serum CGRP levels were significantly lower (50 +/- 19 versus 90 +/- 23 pg/mL, P < .001). Similarly, the frequency of newborns with nondetectable PTHrP levels in umbilical serum was significantly higher (68% versus 36%, P < .05), whereas the levels of CGRP were significantly lower (67 +/- 17 versus 79 +/- 16 pg/mL, P < .05). Magnesium sulfate treatment resulted in a significant increase in maternal circulating CGRP levels (64 +/- 17 versus 47 +/- 18 pg/mL, P < .05) with no changes in PTHrP. Conclusion: Maternal circulating PTHrP and CGRP concentrations were significantly lower in women with preeclampsia, which may contribute to the development and maintenance of hypertension during pregnancy. Furthermore, magnesium sulfate therapy increased the levels of CGRP in the maternal circulation. (Obstet Gynecol 2001;97: 893-7. (C) 2001 by The American College of Obstetricians and Gynecologists.).