Hypocalciuria of preeclampsia is independent of parathyroid hormone level.

Hypocalciuria is a feature of preeclampsia. The roles of parathyroid hormone (PTH) and vitamin D 1,25(OH)2D3 (calcitriol) in its pathogenesis have not yet been determined. Fourteen preeclamptic women were compared with 12 women with chronic hypertension and 11 normotensives, all in the third trimester. Preeclamptics had the lowest urinary calcium excretion rate (62.1 +/- 32.8 mg/24 hours) compared with chronic hypertensive women (162.6 +/- 97.8 mg/24 hours) and normotensive controls (225.6 = 146.9 mg/24 hours) (P less than .05). Serum PTH was lowest in preeclamptics (9.8 +/- 5.5 pg/mL), in contrast to the chronic hypertensives (18.5 +/- 2.7 pg/mL) and normotensives (16.4 +/- 3.2 pg/mL) (P less than .005). Similarly, urinary cyclic adenosine monophosphate (cAMP) excretion was 2.9 +/- 1.4 mumol/24 hours in the preeclamptics, 5.1 +/- 1.7 mumol/24 hours in the chronic hypertensives, and 4.6 +/- 1.3 mumol/24 hours in the normotensive group (P less than .05). These data suggest that the mechanism of hypocalciuria in preeclampsia is independent of the PTH-calcitriol axis. Therefore, it is suggested that the hypocalciuria of preeclampsia is due to intrinsic renal tubular dysfunction.