Calcium metabolism in normal pregnancy: a longitudinal study

Abnormalities of the rib growth plate and the periphysis of previously healthy infants and toddlers dying suddenly and unexpectedly

AIMS

Histological examination of the rib is of critical value in perinatal pathology and points to the health of the child preceding death. The rib is considered ideal because it is the most rapidly growing long bone in infants and demonstrates growth arrest at onset of the insult. We aimed to identify: (1) changes in the perichondrial ring (PR) in the rib of infants and children up to 16 months of age dying suddenly at our institution and (2) any association with presence of histological changes of vitamin D deficiency (VDD)/metabolic bone disease (MBD) in the growth plate.

METHODS

Retrospective review of the PR histology and comparison with the presence or absence of histological features of VDD in the growth plate of 167 cases. The cases were anonymised and divided in six age/gender categories.

RESULTS

Periphyseal abnormalities were only seen in 38% of the cases; of whom 33% had established and 67% had mild changes. Only 14.5% of cases with established histological appearance of VDD at the growth plate had significant PR abnormality; of whom majority (83%) were ≤3 months of age and none ≥9 months old, reflecting a temporal relation with birth and beyond the perinatal period.

CONCLUSION

The histological changes in the PR are significantly associated with histological changes of VDD/MBD at the rib growth plate with an OR of 3.04.

Pregnancy-Related Bone Mineral and Microarchitecture Changes in Women Aged 30 to 45 Years

At birth, the neonatal skeleton contains 20 to 30 g calcium (Ca). It is hypothesized maternal bone mineral may be mobilized to support fetal skeletal development, although evidence of pregnancy-induced mineral mobilization is limited. We recruited healthy pregnant (n = 53) and non-pregnant non-lactating (NPNL; n = 37) women aged 30 to 45 years (mean age 35.4 ± 3.8 years) and obtained peripheral quantitative computed tomography (pQCT) and high-resolution pQCT (HR-pQCT) scans from the tibia and radius at 14 to 16 and 34 to 36 weeks of pregnancy, with a similar scan interval for NPNL. Multiple linear regression models were used to assess group differences in change between baseline and follow-up; differences are expressed as standard deviation scores (SDS) ± SEM. Decreases in volumetric bone mineral density (vBMD) outcomes were found in both groups; however, pregnancy-related decreases for pQCT total and trabecular vBMD were -0.65 ± 0.22 SDS and -0.50 ± 0.23 SDS greater (p < .05). HR-pQCT total and cortical vBMD decreased compared with NPNL by -0.49 ± 0.24 SDS and -0.67 ± 0.23 SDS, respectively; trabecular vBMD decreased in both groups to a similar magnitude. Pregnancy-related changes in bone microarchitecture significantly exceeded NPNL change for trabecular number (0.47 ± 0.23 SDS), trabecular separation (-0.54 ± 0.24 SDS), cortical thickness (-1.01 ± 0.21 SDS), and cortical perimeter (0.78 ± 0.23 SDS). At the proximal radius, cortical vBMD and endosteal circumference increased by 0.50 ± 0.23 SDS and 0.46 ± 0.23 SDS, respectively, compared with NPNL, whereas cortical thickness decreased -0.50 ± 0.22 SDS. Pregnancy-related decreases in total and compartment-specific vBMD exceed age-related change at the distal tibia. Changes at the radius were only evident with pQCT at the cortical-rich proximal site and suggest endosteal resorption. Although the magnitude of these pregnancy-related changes in the appendicular skeleton are small, if they reflect global changes across the skeleton at large, they may contribute substantially to the Ca requirements of the fetus. © 2020 Crown copyright. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.

Accuracy, precision, and error in age estimation of Florida manatees using growth layer groups in earbones

Ages of Florida manatees (Trichechus manatus latirostris) can be estimated by counting annual growth layer groups (GLGs) in the periotic dome portion of the tympanoperiotic complex of their earbones. The Florida Fish and Wildlife Conservation Commission manages an archive of more than 8,700 Florida manatee earbones collected from salvaged carcasses from 1989 to 2017. Our goal was to comprehensively evaluate techniques used to estimate age, given this large sample size and changes to processing protocols and earbone readers over time. We developed new standards for estimating ages from earbones, involving two independent readers to obtain measurements of within- and between-reader precision. To quantify accuracy, precision, and error, 111 earbones from manatees with approximately known ages (first known as calves: “KAC”) and 69 earbones from manatees with minimum known ages (“MKA,” based on photo-identification sighting histories) were processed, and their ages were estimated. There was greater precision within readers (coefficient of variation, CV: 2.4–8.5%) than between readers (CV: 13.1–13.3%). The median of age estimates fell within the true age range for 63.1% of KAC cases and was at least the sighting duration for 75.0% of MKA cases. Age estimates were generally unbiased, as indicated by an average raw error ± SD of −0.05 ± 3.05 years for the KAC group. The absolute error (i.e., absolute value of raw error) of the KAC data set averaged 1.75 ± 2.50 years. Accuracy decreased and error increased with increasing known age, especially for animals over 15 years old, whose ages were mostly underestimated due to increasing levels of resorption (the process of bone turnover that obscures GLGs). Understanding the degree of uncertainty in age estimates will help us assess the utility of age data in manatee population models. We emphasize the importance of standardizing and routinely reviewing age estimation and processing protocols to ensure that age data remain consistent and reliable.

Randomized trial of three doses of vitamin D to reduce deficiency in pregnant Mongolian women

BACKGROUND

In winter in Mongolia, 80% of adults have 25-hydroxyvitamin D (25(OH)D) concentrations <25 nmol/l (<10 ng/ml) and 99% have <50 nmol/l (<20 ng/ml). The vitamin D dose to avert deficiency during pregnancy in this population is unknown.

METHODS

We conducted a randomized, controlled, double-blind trial of daily 600, 2000, or 4000 IU vitamin D₃ for pregnant women in Mongolia (Clinicaltrials.gov #NCT02395081). We examined 25(OH)D concentrations at baseline (12-16 weeks' gestation), 36-40 weeks' gestation and in umbilical cord blood, using enzyme linked fluorescent assay. Sample size was determined to detect 0.4 standard deviation differences in 25(OH)D concentrations with 80% power.

FINDINGS

119 pregnant women were assigned 600 IU, 121 assigned 2000 IU and 120 assigned 4000 IU from February 2015 through December 2016. Eighty-eight percent of participants took ≥80% of assigned supplements. At baseline, 25(OH)D concentrations were similar across arms; overall mean ± standard deviation concentration was 19 ± 22 nmol/l; 91% were < 50 nmol/l. At 36-40 weeks, 25(OH)D concentrations increased to 46 ± 21, 70 ± 23, and 81 ± 29 nmol/l for women assigned 600, 2000, and 4000 IU, respectively (p < 0.0001 across arms; p = 0.002 for 2000 vs. 4000 IU). Mean umbilical cord 25(OH)D concentrations differed by study arm (p < 0.0001 across arms; p < 0.0001 for 2000 vs. 4000 IU) and were proportional to maternal concentrations. There were no adverse events, including hypercalcemia, attributable to vitamin D supplementation.

INTERPRETATION

Daily supplementation of 4000 IU during pregnancy is safe and achieved higher maternal and neonatal 25(OH)D concentrations than 2000 IU. Daily 600 IU supplements are insufficient to prevent vitamin D deficiency in Mongolia. FUND: Anonymous foundation and Brigham and Women's Hospital.

Serum Calcium and Magnesium Levels in Normal Ghanaian Pregnant Women: A Comparative Cross-Sectional Study

BACKGROUND:

Pregnancy is described as a normal physiologic state associated with various biochemical changes. Magnesium and calcium are essential macronutrients required for foetal growth. Complications associated with their deficiency during normal pregnancy include; low neonatal birth weight, pre-eclampsia, eclampsia and preterm labour. Changes in serum levels of magnesium and calcium in normal pregnancy have not been extensively studied among Ghanaian women.

AIM:

To determine the variation in serum magnesium and calcium levels with gestational age in normal pregnancy in Ghanaian women.

METHODS:

A hospital-based comparative cross-sectional study was conducted among 32 normal non-pregnant women (Group A) and 100 normal pregnant women (Group B) attending the clinic at the Korle-Bu Teaching hospital. The group B pregnant women were further divided into Group B1 (n = 33), Group B2 (n = 37) and Group B3 (n = 30) based on their pregnancy gestation as first, second and third trimester respectively. Blood samples were obtained from the antecubital vein of subjects and total serum calcium, magnesium, protein and albumin were estimated. Data obtained were analysed using SPSS for windows version 20. Analysis of variance (ANOVA) was employed to determine the statistical differences between the groups. A p-value of ≤ 0.05 was considered significant.

RESULTS:

Mean serum total calcium and magnesium in first, second and third trimester normal pregnant women were 2.14 ± 0.16, 2.13 ± 0.44, 2.13 ± 0.35 mmol/L and 0.77 ± 0.11, 0.77 ± 0.16 and 0.76 ± 0.14 mmol/L respectively. Mean serum total calcium and magnesium levels in non-pregnant women were 2.20 ± 0.16 and 0.80 ± 0.10 mmol/L respectively. There was a statistically non-significant difference in serum total calcium and magnesium between non-pregnant and normal pregnant women, with p-values of 0.779 and 0.566 respectively. Mean total serum protein and albumin in first, second and third-trimester normal pregnant women were 68.42 ± 10.37, 70.46 ± 6.84, 66.70 ± 7.83 g/L and 39.92 ± 3.22, 40.75 ± 8.06, 38.26 ± 3.02 g/L respectively. Mean total serum protein and albumin in non-pregnant women were 73.13 ± 7.02 and 42.94 ± 3.03 g/L respectively. Mean total serum protein and albumin levels were lower in pregnant women as compared to non-pregnant women with the difference being significant in the third trimester (p-values of 0.012 and 0.002).

CONCLUSION:

Total serum calcium and magnesium levels in normal pregnancy were non-significantly lower compared to non-pregnant women in Ghana. There was a reduction in total serum protein, and albumin levels during pregnancy with a significant reduction noticed during the third trimester compared to the non-pregnant state.

Gestation-Specific Changes in the Anatomy and Physiology of Healthy Pregnant Women: An Extended Repository of Model Parameters for Physiologically Based Pharmacokinetic Modeling in Pregnancy

BACKGROUND

In the past years, several repositories for anatomical and physiological parameters required for physiologically based pharmacokinetic modeling in pregnant women have been published. While providing a good basis, some important aspects can be further detailed. For example, they did not account for the variability associated with parameters or were lacking key parameters necessary for developing more detailed mechanistic pregnancy physiologically based pharmacokinetic models, such as the composition of pregnancy-specific tissues.

OBJECTIVES

The aim of this meta-analysis was to provide an updated and extended database of anatomical and physiological parameters in healthy pregnant women that also accounts for changes in the variability of a parameter throughout gestation and for the composition of pregnancy-specific tissues.

METHODS

A systematic literature search was carried out to collect study data on pregnancy-related changes of anatomical and physiological parameters. For each parameter, a set of mathematical functions was fitted to the data and to the standard deviation observed among the data. The best performing functions were selected based on numerical and visual diagnostics as well as based on physiological plausibility.

RESULTS

The literature search yielded 473 studies, 302 of which met the criteria to be further analyzed and compiled in a database. In total, the database encompassed 7729 data. Although the availability of quantitative data for some parameters remained limited, mathematical functions could be generated for many important parameters. Gaps were filled based on qualitative knowledge and based on physiologically plausible assumptions.

CONCLUSION

The presented results facilitate the integration of pregnancy-dependent changes in anatomy and physiology into mechanistic population physiologically based pharmacokinetic models. Such models can ultimately provide a valuable tool to investigate the pharmacokinetics during pregnancy in silico and support informed decision making regarding optimal dosing regimens in this vulnerable special population.

Prenatal exposure to lead in France: Cord-blood levels and associated factors: Results from the perinatal component of the French Longitudinal Study since Childhood (Elfe)

BACKGROUND

As a result of the ban on lead in gasoline on 2nd January 2000, the French population's exposure to lead has decreased in recent years. However, because of the acknowledged harmful cognitive effects of lead even at low levels, lead exposure remains a major public health issue. In France, few biomonitoring data are available for exposure to lead in pregnant women and newborn. The purpose of the perinatal component of the French human biomonitoring (HBM) program was to describe levels of various biomarkers of exposure to several environmental pollutants, including lead, among mother-baby pairs. In this paper, we aimed to describe the distribution of cord blood lead levels (CBLL) in French mother-baby pairs, and to estimate the contribution of the main lead exposure risk factors to these levels.

METHOD

A total of 1968 mother-baby pairs selected from the participants of the perinatal component of the French HBM program were included in the study on lead. Lead levels were analyzed in cord blood collected at child delivery by inductively coupled plasma-mass spectrometry (ICP-MS). The data collected included biological sample, socio-demographic characteristics, environmental and occupational exposure, and information on dietary factors.

RESULTS

CBLL were quantified for 99.5% of the sample. The CBLL geometric mean was 8.30 μg/l (95% CI [7.94-8.68]) with a 95th percentile of 24.3 μg/l (95% CI [20.7-27.1]). Factors significantly associated with CBLL were tap water consumption, alcohol consumption, shellfish consumption, vegetable consumption, bread consumption, smoking, and the mother being born in countries where lead is often used.

CONCLUSION

This study provides the first reference value for CBLL in a random sample of mother-baby pairs not particularly exposed to high levels of lead (24.3 μg/l). A substantial decrease in CBLL over time was observed, which confirms the decrease of exposure to lead among the general population. CBLL observed in this French study were in the range of those found in recent surveys conducted in other countries.

A study of bone turnover markers in gestational diabetes mellitus

INTRODUCTION

Gestational diabetes is defined as carbohydrate intolerance resulting in hyperglycemia of variable severity with the first recognition during pregnancy. Established risk factors for gestational diabetes mellitus (GDM) are maternal age, obesity, family history of diabetes, etc. Vitamin D, parathyroid hormone (PTH), and various other hormones are known for their function in maintaining calcium and phosphorous homeostatic. Furthermore, Vitamin D, PTH serum ionized calcium, and alkaline phosphatase (ALP) have been reported to be altered with glucose homeostasis. The present study compares the bone markers in pregnant women with and without gestational diabetes.

MATERIALS AND METHODS

This cross-sectional study was conducted at outpatient antenatal check-up clinic and outpatient diabetic clinics at J. N. Medical College and Hospital, Aligarh. One hundred pregnant females, of which fifty with GDM and fifty without GDM, were included in the study from January 2014 to November 2015. Detailed history, physical examination, and anthropometric measurement were done. Bone turnover markers in the form of Vitamin D, parathyroid hormone, serum ionized calcium, and serum ALP were measured in pregnant women who had gestational diabetes which was compared with normal pregnant women.

RESULTS

In our study, the mean age of participate of GDM group was 28.2 ± 3 years, while the mean age group in non-GDM group was 25.44 ± 2.78 years. Ionized calcium in GDM was found to be 4.606 ± 0.354 mEq/L, while in non-GDM, it was 4.548 ± 0.384 mEq/L, P = 0.430. Vitamin D came out to be 21.80 ± 9.48 ng/ml, while it was 32.346 ± 8.37 ng/ml in non-GDM group. Serum PTH in GDM group was 71.436 ± 36.189 pg/ml and 37.168 ± 8.128 pg/ml in nondiabetic gestational group. Serum ALP in GDM group was 9.1 ± 4.56 KA U/dl and 6.98 ± 2.2 KA U/dl in nondiabetic gestational group, P - 0.0038. In GDM group, there was a significant negative linear correlation between PTH and 25-hydroxyvitamin D with research correlation coefficient r = -0.9073, P = 0; there was a significant positive linear correlation coefficient between PTH and ALP with Persian correlation coefficient r = 0.6597, P = 0; there was no statistically significant correlation between PTH and ionized calcium r = 0.1416, P = 0.3267.

CONCLUSION

All GDM subjects should ideally be screened for serum calcium, vitamin D, PTH, ALP. If found impaired should immediately be corrected in order to prevent its adverse effects on maternal and fetal outcome. Vitamin D supplementation should ideally be initiated in all GDM females even if the above parameters are not investigated in Indian setup.

Biomarkers of exposure to environmental contaminants in French pregnant women from the Elfe cohort in 2011

BACKGROUND

As part of the perinatal component of the French Human Biomonitoring (HBM) program, biomarkers levels of various chemicals have been described among pregnant women having given birth in continental France in 2011 and who have been enrolled in the Elfe cohort (French Longitudinal Study since Childhood). This paper describes the design of the study and provides main descriptive results regarding exposure biomarkers levels.

METHODS

Exposure biomarkers were measured in biological samples collected at delivery from pregnant women randomly selected among the participants in the clinical and biological component of the Elfe cohort (n=4145). The geometric mean and percentiles of the levels distribution were estimated for each biomarker. The sampling design was taken into account in order to obtain estimates representative of the French pregnant women in 2011.

RESULTS

Results provide a nation-wide representative description of biomarker levels for important environmental contaminants among pregnant women who gave birth in France in 2011. Bisphenol A (BPA), and some metabolites of phthalates, pesticides (mainly pyrethroids), dioxins, furans, polychlorobiphenyls (PCBs), brominated flame retardants (BFRs), perfluorinated compounds (PFCs) and metals (except uranium) were quantified in almost 100% of the pregnant women. Some compounds showed a downward trend compared to previous studies (lead, mercury), but others did not (pyrethroids) and should be further monitored.

CONCLUSION AND PERSPECTIVES

The present results show that French pregnant women are exposed to a wide variety of pollutants, including some that have been banned or restricted in France.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery

During pregnancy and lactation, female physiology adapts to meet the added nutritional demands of fetuses and neonates. An average full-term fetus contains ∼30 g calcium, 20 g phosphorus, and 0.8 g magnesium. About 80% of mineral is accreted during the third trimester; calcium transfers at 300-350 mg/day during the final 6 wk. The neonate requires 200 mg calcium daily from milk during the first 6 mo, and 120 mg calcium from milk during the second 6 mo (additional calcium comes from solid foods). Calcium transfers can be more than double and triple these values, respectively, in women who nurse twins and triplets. About 25% of dietary calcium is normally absorbed in healthy adults. Average maternal calcium intakes in American and Canadian women are insufficient to meet the fetal and neonatal calcium requirements if normal efficiency of intestinal calcium absorption is relied upon. However, several adaptations are invoked to meet the fetal and neonatal demands for mineral without requiring increased intakes by the mother. During pregnancy the efficiency of intestinal calcium absorption doubles, whereas during lactation the maternal skeleton is resorbed to provide calcium for milk. This review addresses our current knowledge regarding maternal adaptations in mineral and skeletal homeostasis that occur during pregnancy, lactation, and post-weaning recovery. Also considered are the impacts that these adaptations have on biochemical and hormonal parameters of mineral homeostasis, the consequences for long-term skeletal health, and the presentation and management of disorders of mineral and bone metabolism.

Calcium economy in human pregnancy and lactation

Pregnancy and lactation are times of additional demand for Ca. Ca is transferred across the placenta for fetal skeletal mineralisation, and supplied to the mammary gland for secretion into breast milk. In theory, these additional maternal requirements could be met through mobilisation of Ca from the skeleton, increased intestinal Ca absorption efficiency, enhanced renal Ca retention or greater dietary Ca intake. The extent to which any or all of these apply, the underpinning biological mechanisms and the possible consequences for maternal and infant bone health in the short and long term are the focus of the present review. The complexities in the methodological aspects of interpreting the literature in this area are highlighted and the inter-individual variation in the response to pregnancy and lactation is reviewed. In summary, human pregnancy and lactation are associated with changes in Ca and bone metabolism that support the transfer of Ca between mother and child. The changes generally appear to be independent of maternal Ca supply in populations where Ca intakes are close to current recommendations. Evidence suggests that the processes are physiological in humans and that they provide sufficient Ca for fetal growth and breast-milk production, without relying on an increase in dietary Ca intake or compromising long-term maternal bone health. Further research is needed to determine the limitations of the maternal response to the Ca demands of pregnancy and lactation, especially among mothers with marginal and low dietary Ca intake, and to define vitamin D adequacy for reproductive women.

Implications of vitamin D deficiency in pregnancy and lactation

Vitamin D is an essential fat soluble vitamin and a key modulator of calcium metabolism in children and adults. Because calcium demands increase in the third trimester of pregnancy, vitamin D status becomes crucial for maternal health, fetal skeletal growth, and optimal maternal and fetal outcomes. Vitamin D deficiency is common in pregnant women (5-50%) and in breastfed infants (10-56%), despite the widespread use of prenatal vitamins, because these are inadequate to maintain normal vitamin D levels (>or=32 ng/mL). Adverse health outcomes such as preeclampsia, low birthweight, neonatal hypocalcemia, poor postnatal growth, bone fragility, and increased incidence of autoimmune diseases have been linked to low vitamin D levels during pregnancy and infancy. Studies are underway to establish the recommended daily doses of vitamin D in pregnant women. This review discusses vitamin D metabolism and the implications of vitamin D deficiency in pregnancy and lactation.

Profound Vitamin D Deficiency in a Diverse Group of Women during Pregnancy Living in a Sun-Rich Environment at Latitude 32°N

OBJECTIVE

Determine prevalence of vitamin D deficiency (VDD) in a diverse group of women presenting for obstetrical care at two community health centers in South Carolina at latitude 32°N.

METHODS AND DESIGN

Any pregnant woman presenting for care at 2 community health centers was eligible to participate. Sociodemographic and clinical history were recorded. A single blood sample was taken to measure circulating 25(OH)D as indicator of vitamin D status [25(OH)D < 20 ng/mL (50 nmol/L deficiency; <32 ng/mL (80 nmol/L) insufficiency]. Total serum calcium, phosphorus, creatinine, and intact parathyroid hormone also were measured.

RESULTS

559 women, [mean age 25.0 ± 5.4 (range 14-43) years] participated: African American (48%), Hispanic (38%), Caucasian/Other (14%). Mean gestational age was 18.5 ± 8.4 (median 14.6, range 6.4-39.6) weeks' gestation. 48% were VDD; an additional 37% insufficient. Greatest degree was in the African American women (68% deficient; 94% insufficient). In multivariable regression, 25(OH)D retained a significant negative association with PTH (P < .001).

CONCLUSIONS

VDD was high in a diverse group of women, greatest in those of darker pigmentation. The negative correlation between 25(OH)D and PTH confirms their corroborative use as biomarkers of VDD. These findings raise the issue of adequacy of current vitamin D recommendations for pregnant women.

Calcium in midpregnancy

OBJECTIVE

To establish reference value for serum calcium concentration and urinary calcium excretion during mid pregnancy and to find out variation of calcium intake in pregnant women.

MATERIALS AND METHODS

This was a cross sectional study conducted in antenatal clinic of department of Obstetrics and Gynaecology. A total of 543 pregnant women with pregnancy period of second trimester were enrolled for the study. Eligible healthy, vegetarian primigravid women provided serum and 24 h urinary samples for determination of serum calcium and urinary calcium excretion. Dietary intake calculated by 3-day recall method. Variation of calcium intake according to various demographic characteristics was noted.

RESULTS

Statistical analysis done with SPSS software. The mean total serum calcium and 24 h urinary calcium and dietary intake of calcium were 8.1+/-1.5 mg/dl (5.1-11.9), 129.56+/-67.08 mg (40.5-400) and 324.37+/-199.47 mg/day (85.71-910.71) respectively. The 95th percentiles for serum calcium were 10.56 mg/dl and urinary calcium excretion was 280.70 mg/24 h. Educational level, monthly income and height were positive correlated with calcium intake.

CONCLUSION

This preliminary study defines the first standard value for calcium status in pregnant second trimester females of northern India. Calcium intake in pregnant females is affected by various demographic characteristics. There is need to change dietary pattern by improving education and socio-economic level.

Calcium metabolism in pregnancy

During pregnancy and lactation there are many changes in maternal calcium physiology which maintain homeostasis in the face of greatly altered calcium balance. In the course of fetal growth and development, 30g of calcium is incorporated into the fetus by term, an amount derived wholly from the maternal system. Most of this accumulates in the latter half of pregnancy, representing a net transfer of 200mg calcium/day (5mmoles). The fact that this is not achieved at the expense of the maternal skeleton is testimony to the conservative and protective adjustments that are seen in calcium metabolism in pregnancy. Furthermore, the changes must persist both in the puerperium and later when lactation presents a source of continuing maternal calcium loss to the suckling infant. The calcium content of human breast milk s i 6–9mmols calcium/l, two to three times the maternal serum level. In the course of one week a normal breast-fed at term infant takes two to three litres of milk, containing 10–30mmols of calcium. The maternal daily calcium intake recommended by the World Health Organization s i 1.25g (30mmol) of which only 25% is absorbed. Thus calcium loss from mother to baby is significant and may not be replaced by diet in many parts of the world.

Expression of prolactin receptor and prolactin in normal and malignant thyroid: a tissue microarray study

OBJECTIVE

There is increasing evidence involving prolactin (PRL) and its receptor (PRLR) in the development of different cancers. The aim of the present study was to investigate the expression of PRLR and PRL in human thyroid tissues.

DESIGN AND METHODS

Using tissue microarray (TMA) by immunohistochemical staining, we examined the expression level of PRLR and PRL in 314 specimens from 71 thyroid cancer patients and 15 normal thyroid samples.

RESULTS

Expression of the PRLR was observed in 93.3% of normal thyroid samples and in 76.1% of all thyroid cancers, while expression of PRL was observed in only 10% of medullary thyroid carcinomas and not at all in the other specimens, whether normal or neoplastic. Moreover, results suggested an overexpression of PRLR in 70% of medullary thyroid carcinomas, whereas 53.3% of poorly differentiated thyroid carcinomas showed a negative pattern of staining (p = 0.014 vs normal).

CONCLUSIONS

Present data revealed, for the first time, a widespread expression of PRLR in normal and neoplastic human thyroid tissues as well as a scarce expression of PRL, observed only in a few medullary thyroid carcinomas. Whether the overexpression of PRLR observed in medullary thyroid carcinomas or the underexpression of PRLR observed in poorly differentiated thyroid carcinomas play a contributory role in the oncogenesis of these tumors remains to be determined.

Is lead considered as a risk factor for high blood pressure during menopause period among Saudi women?

This case-control study was designed to examine the association between blood lead levels and high blood pressure in a restricted subpopulation, Saudi women who were 45-93-year old, during or after menopausal period and not occupationally exposed to lead. Blood lead levels were assessed in 100 women with hypertension and 85 control subjects. Lead concentrations were measured in the whole blood using flameless atomic absorption spectrophotometry. Blood pressure measurements were performed according to the World Health Organization recommendations. Results revealed that the mean blood lead levels for hypertensive were 47.52+/-39.26 and 45.59+/-28.55 microg/l for controls. Participants were classified according to the median of blood lead levels in order to compute odds ratios. After controlling a number of potential confounding variables, the multiple logistic regression analysis revealed that women with blood lead levels of > or = 38.6 microg/l were 5.27 times more likely to be hypertensive than those with blood lead levels of < 38.6 microg/l, but of borderline significance (p = 0.06). Although such observation might support the hypothesis that the depletion of lead from bones during menopause increases blood lead levels placing women at increased risk for high blood pressure, there is a need for further studies with larger number of subjects. A number of risk factors, which were suspected to influence blood lead levels, were also investigated. Use of Kohl, duration of its use, osteoporosis disease and intake of calcium supplements were significantly associated with blood lead levels.

Effects of pregnancy and lactation on bone mineral density, and their relation to the serum calcium, phosphorus, calcitonin and parathyroid hormone levels in rats

The aim of this study was to evaluate the net changes in bone mineral density (BMD) during the reproductive cycle, and their relation with changes in serum calcium (Ca), phosphorus (P), PTH and calcitonin levels in rats. Twenty-seven female Wistar rats were included in this study. They were divided into three groups as pregnant, lactating and control groups. BMDs of lumbar vertebrates, femoral and tibial bones, and Ca, P, calcitonin and PTH levels were measured at the end of pregnancy, at the end of lactation and in nulliparous controls. In the pregnant group, the BMDs of rats were significantly higher in lumbar vertebrates, femoral and tibia bones than those of the control group (p<0.05). Their PTH and Ca levels were significantly lower than the control group (p<0.05). However, no statistically significant difference was found regarding P and calcitonin levels when compared to those of the control group. In the lactating group, the BMDs were significantly lower in lumbar vertebrates, femoral and tibia bones than those seen in the control and pregnant groups (p<0.05). Ca and PTH levels were significantly higher in lactating rats than in those of pregnant rats (p<0.005). Normal pregnancy increases BMD in rats, whereas lactation decreases it. Change in PTH levels is supposed to contribute to the mineralization and demineralization of the skeleton during pregnancy and lactation, respectively.

Calcium in pregnancy and lactation

Pregnancy and lactation are periods of high calcium requirement. This review highlights recent advances in our understanding of calcium and bone metabolism during human pregnancy and lactation and discusses the findings in relation to the calcium nutrition of the mother. The evidence indicates that pregnancy and lactation are characterized by physiological adaptive processes that are independent of maternal calcium intake and that provide the calcium necessary for fetal growth and breast-milk production without requiring an increase in maternal calcium intake. There are firm data that demonstrate that a low calcium intake during lactation does not lead to impaired lactational performance or to exaggerated bone loss. However, more research is required to define whether a low calcium intake prior to or during pregnancy can have deleterious effects on reproductive and lactational performance, and on the long-term health of the mother and child.

Choosing an oestrogen replacement therapy in young adult women with Turner syndrome

OBJECTIVE

Hormone replacement therapy (HRT) is prescribed to most patients with Turner syndrome (TS) although its use in adult TS patients has not been scientifically evaluated. The present study was performed to compare the short-term effects in adult women with Turner syndrome of low-dose oral conjugated oestrogen (0.625 mg, CE) with relatively high dose ethinyl oestradiol (30 microg, EE2); both combined with an oral progestin.

DESIGN AND PATIENTS

After 4 months off HRT, 17 young, otherwise healthy women with TS were enrolled in a random, unblinded, crossover study of the two oestrogenic preparations, each given for 6 months.

MEASUREMENTS

We compared parameters of oestrogenic activity that would cover immediate changes in hormone levels, biochemistry, bone turnover, uterine and cardiac variables, which constitute risk factors for later development of diabetes, atherosclerosis, osteoporosis and aortic dissection.

RESULTS

Serum FSH returned to normal follicular phase levels only on the EE2 regimen. The hypotrophic endometria normalized with either of the two oestrogen regimens with no excessive hypertrophy. Hyperinsulinaemia was suppressed to normal by both EE2 and CE. PTH and 1,25-dihydroxyvitamin D levels increased on HRT (EE2 > CE), and phosphorus decreased. Alkaline phosphatase, osteocalcin and urinary deoxypyridinoline cross-links (DPD) were high off therapy; the former two suppressed to high-normal levels on the EE2 regimen, but not on CE, and DPD did not normalize with either HRT. Lipid profiles in these young TS patients were normal. Liver enzymes were mildly elevated off therapy and suppressed to normal levels on both regimens, but more so with EE2.

CONCLUSIONS

The risk factors embodied in hyperinsulinaemia and enhanced bone turnover which, ultimately, have consequences for TS morbidity, are minimized by HRT. In the short term, neither regimen is effective for bone turnover in adult women with Turner syndrome.

Calcium metabolism in pre-eclampsia

OBJECTIVES

To study calcium metabolism in pre-eclampsia and normotensive gravid women.

METHOD

Ten milliliters of heparinized blood samples and 24-h urine samples were collected from 50 pre-eclamptic and 50 normotensive primigravidae. Blood samples were studied for calcium uptake, intracellular calcium level and calcium-dependent adenosine triphosphatase activity of red blood cell ghost. Urinary calcium excretion was estimated from the 24-h urine samples. These values were compared in the two groups.

RESULTS

The mean gestational age at recruitment was similar in both the groups. The mean maternal age was 24.28 +/- 2.41 years in pre-eclamptic and 23.48 +/- 4.16 years in normotensive women. In pre-eclampsia 24-h urinary calcium excretion (71.20 +/- 22.95 mg/day) and calcium-dependent ATPase activity (10.78 +/- 2.40 nmol/Pi/mg protein/min) was significantly lower compared to normotensive primigravidae (calcium excretion = 189.24 +/- 57.06 mg/day; Ca2+-dependent ATPase = 12.64 +/- 2.42 nmolPi/mg /protein per min; P < 0.001). Intracellular calcium levels and calcium uptake at 10 min by red blood cells were significantly higher in pre-eclampsia (P < 0.05). Calcium uptake by red blood cells at 20 and 30 min was similar in both groups.

CONCLUSION

Pre-eclampsia is associated with increased levels of intracellular calcium, decreased calcium-dependent ATPase activity of erythrocytes and hypocalciuria.

Intracellular and extracellular, ionized and total magnesium in pre-eclampsia and uncomplicated pregnancy

Magnesium (Mg) and calcium (CA) concentrations in women with pre-eclampsia, women with an uncomplicated pregnancy and non-pregnant women were compared. Ionized serum magnesium and calcium concentrations and intracellular magnesium concentrations were measured in 15 pregnant women with severe pre-eclampsia, 34 uncomplicated pregnant women early, at midterm and preterm in their pregnancy and 24 non-pregnant women. The ionized calcium concentration did not chance during normal pregnancy or during pre-eclampsia relative to non-pregnant women. In contrast, elevated total and ionized magnesium serum concentrations were found in women with severe pre-eclampsia (total Mg = 0.85+/-0.11 mM, ionized Mg = 0.61+/-0.06 mM) relative to uncomplicated pregnant women (total Mg = 0.72+/-0.06 mM, ionized Mg = 0.53+/-0.03 mM). Total magnesium in pre-eclamptic women were similar to non-pregnant women. Intracellular ionized and total magnesium concentrations in mononuclear blood cells and erythrocytes were similar in pre-eclamptic women and women with uncomplicated pregnancy. Serum magnesium concentrations are elevated in severe pre-eclamptic women relative to women with uncomplicated pregnancy and are related to birth weight and gestational age at delivery. There may be a causal relationship since magnesium is involved in blood pressure regulation through an intracellular inhibition of NO synthase in endothelial cells.

Cure of hyperparathyroidism in pregnancy by sternotomy and removal of a mediastinal parathyroid adenoma

Primary hyperparathyroidism is rarely reported during pregnancy but can cause significant maternal and neonatal morbidity. We report a case of hyperparathyroidism during pregnancy requiring a median sternotomy for resection of a mediastinal parathyroid adenoma. Surgery resulted in normalisation of serum calcium, resolution of symptoms, and prevented neonatal hypocalcaemia.

Parathyroid hormone-related protein levels in maternal and cord blood

OBJECTIVE

Our purpose was to determine the plasma levels of parathyroid hormone-related protein in normal pregnant women in each trimester, at 1 month post partum in women using different feeding methods, and in umbilical venous blood.

STUDY DESIGN

We studied 40 healthy nonpregnant women, 90 healthy pregnant women (30 in the each trimester), and 140 postpartum women (breast-feeding 74, mixed feeding 33, bottle feeding 33). We also measured the parathyroid hormone-related protein level in umbilical venous blood in 24 women.

RESULTS

The means and SDs of the plasma parathyroid hormone-related protein level were 1.04 +/- 0.11 pmol/L (0.81 to 1.26 pmol/L) in nonpregnant women, 1.06 +/- 0.19 pmol/L (0.69 to 1.48 pmol/L) in pregnant women in the first trimester, 1.10 +/- 0.19 pmol/L (0.80 to 1.50 pmol/L) in pregnant women in the second trimester, and 1.17 +/- 0.16 pmol/L (0.86 to 1.57 pmol/L) in pregnant women in the third trimester. At postpartum month 1 the plasma level of parathyroid hormone-related protein was 1.25 +/- 0.23 pmol/L (0.83 to 2.01 pmol/L) in breast-feeding women, 1.17 +/- 0.16 pmol/L (0.84 to 1.53 pmol/L) in mixed-feeding women, and 1.03 +/- 0.16 pmol/L (0.74 to 1.43 pmol/L) in bottle-feeding women. The umbilical venous blood level of parathyroid hormone-related protein was 1.33 +/- 0.32 pmol/L (0.84 to 2.11 pmol/L). The mean plasma level of parathyroid hormone-related protein increased throughout pregnancy and was significantly high in the third trimester and closely associated with the degree of breast-feeding at 1 month post partum. The parathyroid hormone-related protein level in umbilical venous blood was significantly higher than those in any groups of pregnant women.

CONCLUSIONS

Parathyroid hormone-related protein produced in the fetoplacental unit, the breast, or both can reach the maternal circulation.

Hyperparathyroidism in pregnancy: diagnostic dilemma?

Primary hyperparathyroidism is rarely encountered in pregnancy. Because the symptoms may be variable in nature, the diagnosis may be delayed with an increase in maternal and perinatal morbidity or mortality. Several of the symptoms and clinical findings in hyperparathyroidism may also be present with preeclampsia, thus causing difficulty in distinguishing one from the other. Our case report describes a pregnant patient in the third trimester with HELLP syndrome and primary hyperparathyroidism.

A prospective study of calciotropic hormones in pregnancy and post partum: reciprocal changes in serum intact parathyroid hormone and 1,25-dihydroxyvitamin D

OBJECTIVE

The purpose of this study was to examine the hormones regulating calcium homeostasis longitudinally in pregnancy and post partum.

STUDY DESIGN

Twenty-three women with normal pregnancies were studied in the second and third trimesters and post partum. At each time blood was analyzed for ionized calcium, vitamin D metabolites, and intact parathyroid hormone, and a 24-hour urine specimen was analyzed for creatinine, calcium, and sodium.

RESULTS

Urinary calcium excretion was 250% to 300% higher during pregnancy than post partum (p < 0.00001). 1,25-Dihydroxyvitamin D levels were equivalent in the second and third trimesters but were twofold higher than postpartum values (p < 0.01). Ionized calcium was similar at all time points. Intact parathyroid hormone in the second and third trimesters was 50% of postpartum levels (p < 0.001).

CONCLUSION

Pregnancy is associated with an increase in the levels of 1,25-dihydroxyvitamin D and a concomitant reciprocal fall in intact parathyroid hormone levels. The increase in serum 1,25-dihydroxyvitamin D values appears to be a key factor in providing for the increase in maternal calcium requirements during pregnancy.

Maternal hematocrit and albumin as predictors of intrauterine growth retardation and preterm delivery

OBJECTIVE

To determine if maternal hematocrit and serum albumin can predict intrauterine growth retardation and/or preterm delivery.

METHODS

Analyses were performed during each trimester of pregnancy to evaluate the predictive value of these two common laboratory parameters as predictors of intrauterine growth retardation and/or prematurity.

RESULTS

1468 women participated in the study. Intrauterine growth retardation occurred in 9.9% and preterm delivery in 6.1%. A significant inverse correlation between hematocrit and albumin and birth weight was found (r = -0.005, p = 0.04, and r = -0.07, p = 0.007, respectively), albumin being a stronger predictor as demonstrated by multiple regression. Low hematocrit at the third visit was associated with a longer pregnancy duration (r = -0.06, p = 0.02). Woman with higher serum albumin levels at the second visit, had a longer pregnancy duration, possibly reflecting a better nutritional status (r = 0.057, p = 0.03). To determine the predictive value of hematocrit and serum albumin, the prevalence of intrauterine growth retardation and premature delivery in the highest quartiles were compared with the lowest, and no significant differences were observed (p > 0.1).

CONCLUSION

Maternal hematocrit and serum albumin concentration cannot be used as useful predictors of intrauterine growth retardation or preterm delivery.

Primary Hyperparathyroidism During Pregnancy

OBJECTIVE

To provide an up-to-date review of primary hyperparathyroidism (HPT) as a complication of pregnancy.

METHODS

We discuss the initial manifestations of primary HPT in pregnant patients, the diagnosis, the differential diagnosis of hypercalcemia, and the recommended treatment strategies.

RESULTS

In the nonpregnant state, 50 to 80% of patients with primary HPT are asymptomatic. In contrast, pregnant patients with primary HPT have a wide variety of symptoms and findings: gastrointestinal symptoms (nausea, vomiting, and anorexia), weakness and fatigue, headaches and confusion, nephrolithiasis, bone disease, pancreatitis, urinary tract infection, and hypertension. Occasionally, neonatal hypocalcemia is the initial manifestation of maternal HPT. Diagnosis of primary HPT during pregnancy is dependent on the clinical history and laboratory findings. In general, management of maternal primary HPT during pregnancy should be individualized and based on the patient's symptoms, general medical condition, severity of disease, and gestational stage at the time of diagnosis. If HPT is diagnosed during the first two trimesters, surgical intervention is the treatment of choice.

CONCLUSION

Although uncommon, HPT during pregnancy may be associated with maternal and perinatal complications. Therefore, clinicians should be aware of the usual characteristics of this disorder and the preferred management options.

Osteoporosis in pregnancy

Osteoporosis has long been described in pregnant women who developed vertebral fractures in the last trimester or shortly after delivery without underlying disorders. However, this condition appears to be relatively rare and the clinical features, associated metabolic abnormalities and a pathological mechanism have not been fully established. This paper reviews available data on osteoporosis and pregnancy and briefly discusses the relationship between pregnancy and bone mass, calcium homeostasis, systemic skeletal hormones and local factors to help explain the pathophysiology of this unique disorder.

Ultrasonographic bone characteristics during normal pregnancy: longitudinal and cross-sectional evaluation

OBJECTIVE

We evaluated the pattern of bone density during pregnancy by radiation-free ultrasonographic densitometry.

STUDY DESIGN

In a longitudinal study we measured bone mineral density in a group of 10 normal primiparous women, from the fourteenth to the thirty-eighth weeks of pregnancy. In a cross-sectional study bone mineral density was determined in a group of 85 normal primiparous women, in different weeks of pregnancy.

RESULTS

In the longitudinal study ultrasonographic bone density was stable in the first part of pregnancy, whereas a significant (p < 0.05) decrease was evidenced during the third trimester. A negative correlation between bone density and weeks of pregnancy (p < 0.0001) was evidenced in the cross-sectional study.

CONCLUSION

During physiologic pregnancy the calcium mobilization from the maternal bone stores to accomplish the fetal needs can cause a significant decrease in maternal bone density in the last trimester of gestation.

Calcium supplementation prevents pregnancy-induced hypertension by increasing the production of vascular nitric oxide

Pregnancy-induced hypertension (PIH) remains a common cause of maternal and fetal morbidity and mortality. During the past 7 years, some progress has been made in the prevention of PIH. Specifically, clinical studies have shown that supplementation with calcium can significantly reduce the frequency of PIH, specially in populations with a low calcium intake. We have suggested that, in such a population, calcium supplementation is a safe and effective measure for reducing the frequency of PIH. Thus, the purpose of this article is to advance a hypothesis about the mechanism by which calcium supplementation reduces the risk of PIH. We propose that dietary calcium supplementation reduces the frequency of PIH by maintaining the serum ionized calcium level which is crucial for the production of endothelial nitric oxide, the increased generation of which maintains the vasodilatation that is characteristic of normal pregnancy.

Calcium metabolism, calcium supplementation and hypertensive disorders of pregnancy

In recent years growing attention has been directed towards the possible role of calcium in the development of pregnancy-induced hypertension and preeclampsia. Several studies describe calcium metabolism in normal and hypertensive pregnancy, but so far, they have shown discrepant and inconsistent results. Intracellular free calcium, which plays an important role in vascular smooth muscle contraction, has been claimed as a pathogenic factor in hypertensive disorders of pregnancy. Although there is discordance in the data, a possible role of intracellular calcium in the development of hypertensive disorders of pregnancy cannot be excluded. Observational studies in pregnant women suggest an inverse association between calcium intake and the incidence of hypertensive disorders of pregnancy. Despite large methodological differences, the results from the calcium supplementation trials support this finding. Although it is rather difficult to isolate the effect of calcium intake from the intake of other mineral elements, results from calcium supplementation trials are supportive for calcium being the most important. Proposed mechanisms by which calcium supplementation may lower blood pressure involve changes in parathyroid hormone (PTH) level, the renin-angiotensin system and calcium as a modifier of vascular agent regulation, but none of these have yet been elucidated. At present, circumstantial evidence suggest a positive role for calcium in the prevention of hypertensive disorders of pregnancy, but definite evidence is lacking and further research is warranted.

Hypocalcemia and pregnancy-induced hypertension produced by low-calcium diet

Recent studies from our laboratory in fasting pregnant ewes with twin gestation have implicated low serum calcium concentration in the etiology of hypertension in pregnancy. We hypothesized that the reduction in serum calcium concentration produced by feeding of a calcium-deficient diet in twin gestation would lead to a significant increase in maternal arterial blood pressure, vascular resistance, and protein in the urine and decreased uterine blood flow. Twenty-five instrumented ewes were used in the present study. After surgery a calcium-deficient diet and deionized water (calcium ion free) were provided ad libitum to 19 animals. Blood pressure, cardiac output, heart rate, and uterine blood flow were monitored every other day. Six control animals were provided with standard Rumilab diet and tap water (group 1). Animals on a low-calcium diet (group 2) were subdivided according to the blood ionized calcium response to low dietary calcium intake. Non-hypocalcemic animals were assigned to group 2a (n = 10), and hypocalcemic animals (calcium concentration below two standard deviations from the control group) were assigned to group 2b (n = 9). In group 2b calcium concentration decreased from 1.03 +/- 0.04 mmol/L on day 110 of gestation to 0.77 +/- 0.03 mmol/L by day 125 of gestation. Arterial blood pressure increased significantly from 76 +/- 2 to 91 +/- 2 mm Hg, and uterine blood flow decreased from 950 +/- 53 to 579 +/- 48 mL/min. Urinary protein increased from 1.7 +/- 0.3 to 10.5 +/- 1.2 g/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Idiopathic osteoporosis during pregnancy

Among the idiopathic forms of osteoporosis, the one developing during pregnancy is the least common and scarcely studied. Poorly understood, it seems to stem from transient failure of calcitropic hormones and decreased osteoblast activity. A 25-year-old patient presented with coxofemoral pain during the last three months of pregnancy, followed by multiple vertebral compression fractures at postpartum. Laboratory, radiological, densitometric and histological examinations led to a diagnosis of idiopathic osteoporosis in pregnancy, once other causes of osteopenia had been ruled out. Bone densitometries performed 12 and 24 months later showed an increase in mineral density, thus demonstrating the self-limited nature of this entity.

Calcium intakes and bone densities of lactating women and breast-fed infants in The Gambia

The calcium required for breast-milk production and infant growth can be a substantial proportion of dietary intakes especially in regions of the world were calcium consumption is low. Insufficient calcium supply might lead to maternal bone loss, reduced breast-milk calcium secretion and impaired infant bone growth. However, changes in calcium absorption and excretion may be sufficient to allow these requirements to be met without affecting maternal or infant health. A limited number of studies have investigated changes in maternal bone mineral, absorption, excretion and metabolism during lactation but few have addressed whether any changes are influenced by calcium intakes. Ongoing detailed research by the MRC Dunn Nutrition Unit in a rural area of The Gambia amongst mothers and infants with habitually low calcium intakes will provide valuable information about calcium needs during lactation and growth.

Pregnancy associated osteoporosis

OBJECTIVE

Previous literature reports have suggested that osteoporosis associated with pregnancy is a rare event. We have examined the prevalence of this condition and compiled data on the largest group of such patients in the literature.

PATIENTS AND DESIGN

With the help of the National Osteoporosis Society 35 women with pregnancy associated osteoporosis were identified. These women were matched with a control group from our already established computer data bank for age, weight, height and calcium status. Detailed questionnaires were sent to the osteoporotic sufferers enquiring about their present condition, past medical and drug history, and their menstrual, lactational and obstetric histories. They were also asked to complete a detailed dietary history to establish their calcium status. A questionnaire was also completed by the parents of these women and the parents of the control group, asking specifically about fracture history.

RESULTS

Twenty-nine women had idiopathic osteoporosis associated with pregnancy, while in six, the condition may have resulted from drug therapy or associated diseases. Pain occurring late in the first full term pregnancy was the most common presentation. The natural history was for the condition to improve with time. There was a significantly higher prevalence of adult related fractures (P < 0.02) occurring at an earlier age in the mothers of these women compared to a control population.

CONCLUSION

We have identified 35 women who have developed osteoporosis during or shortly after pregnancy and in only six of them could a recognized underlying cause be suggested. These findings would suggest that idiopathic osteoporosis associated with pregnancy may be more common than the current literature suggests. The higher prevalence of fractures in the mothers of our population compared to controls raises the question of a possible associated genetic factor in the aetiology of this condition.