Changes in calciotrophic hormones and biochemical markers of bone turnover in normal human pregnancy

Abstract

Plasma concentrations of parathyroid hormone-related protein (PTHrP), parathyroid hormone, alkaline phosphatase, osteocalcin and albumin-adjusted calcium were measured along with nephrogenous cyclic adenosine monophosphate (NcAMP) in 10 normal women longitudinally through pregnancy. In addition, an assessment of bone resorption was made in these same subjects by the measurement in true fasting urine specimens of the calcium/creatinine ratio (Ca/Cr), hydroxyproline/creatinine ratio (HP/Cr), pyridinoline/creatinine ratio (Pyr/Cr) and deoxypyridinoline/creatine ratio (Dpyr/Cr). The PTHrP level rose through pregnancy from (mean +/- SEM) 0.8 +/- 0.2 pmol/l in the first trimester to 2.7 +/- 0.2 pmol/l 6 weeks postpartum (p < 0.0001). Serum alkaline phosphatase rose from 94 +/- 8 U/l (first trimester) to 347 +/- 25 U/l at term (p < 0.0001). A significant positive correlation was evident between PTHrP and alkaline phosphatase up to term (r = 0.44, p < 0.005). Parathyroid hormone concentrations remained unchanged during pregnancy but rose significantly postpartum from 1.8 +/- 0.2 pmol/l (first trimester) to 3.1 +/- 0.5 pmol/l (p < 0.0001). Similarly, osteocalcin, a marker of bone formative activity, remained unchanged through pregnancy but rose significantly at 6 weeks after delivery to 0.38 +/- 0.05 nmol/l from 0.19 +/- 0.03 nmol/l (first trimester) (p = 0.019). No significant change was noted in serum-adjusted calcium or NcAMP, either through pregnancy or at the postpartum assessment. Fasting urinary Ca/Cr fell through pregnancy from 0.70 +/- 0.11 (first trimester) to a nadir of 0.19 +/- 0.04 6 weeks postpartum (p = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-regulating hormones and parathyroid hormone-related peptide in normal human pregnancy and postpartum: a longitudinal study

“…Our present results, together with the findings of others (16,23,26), have not confirmed the pregnancyassociated increases in PTH that have been reported previously. Intact-PTH concentrations tended to decrease during the course of pregnancy, but to increase postpartum, suggesting a state of 'secondary hyperparathyroidism' that may prevail to compensate for the transfer of calcium into the mammary glands for milk production (Fig.…”

“…The stimulus for the increase in calcitriol during pregnancy remains unknown, however. It seems to be unrelated to serum PTH, as the concentrations of intact-PTH were found to decrease with advancing gestation in our pregnant women, which is consistent with several earlier findings (16,(23)(24)(25)(26). In addition, an increase in intact-PTH concentrations postpartum paralleled a decrease in the concentrations of calcitriol (Figs 1 and 2), thus the increase in PTH postpartum did not result in further synthesis of calcitriol -an expected stimulus for enhanced calcium absorption.…”

“…The main objectives of the present study were to evaluate, in a group of women who were not vitamin D-deficient, but who were from an ethnic group (Asian) different than that reported previously (16), the changes in calcitropic hormones (calcitriol, PTH and calcitonin), osteocalcin and PTHrP, in relation to calcium and other minerals, that occurred through the course of pregnancy, at term and 6 weeks postpartum. In addition, the relationships between prolactin, human placental lactogen (hPL) and calcitrophic hormones were also evaluated.…”

Umbilical cord levels of sclerostin, placental weight, and birth weight are predictors of total bone mineral content in neonates

“…Biochemical markers of the maternal bone turnover indicate that bone remodeling is low during the first half of the pregnancy and may increase in the third trimester (5,6,7). Fibroblast growth factor 23 (FGF23) is expressed predominantly in osteoblasts and osteocytes (8).…”

Vitamin D and Human Pregnancy

“…This increase of 1,25(OH) 2 D is independent of a rise in maternal PTH which remains in the low-normal range in the 1 st trimester 43,[66][67][68][69] . Studies have shown that that CYP27B1 activity can be regulated by other sources including parathyroid hormonerelated protein (PTHrP), oestradiol, prolactin (PRL) and placental lactogen [70][71][72] , all of which are increased in pregnancy and which may help explain the rise in 1,25(OH) 2 D independent of PTH responses.…”