Perinatal parathyroid hormone, vitamin D metabolites, and calcitonin in man

Oleanolic acid exerts bone anabolic effects via activation of osteoblastic 25-hydroxyvitamin D 1-alpha hydroxylase

Oleanolic acid (OA) is previously shown to exert bone protective effects in aged animals. However, its role in regulating osteoblastic vitamin D bioactivation, which is one of major causes of age-related bone loss, remains unclear. Our results revealed that treatment of OA significantly increased skeletal CYP27B1 expression and circulating 1,25(OH)2D3 in ovariectomized mice (p <0.01). Moreover, OA upregulated CYP27B1 protein expression and activity, as well as the vitamin D-responsive bone markers alkaline phosphatase (ALP) activity and osteopontin (OPN) protein expression, in human osteoblast-like MG-63 cells (p<0.05). CYP27B1 expression increased along with the osteoblastic differentiation of human bone marrow derived mesenchymal stem cells (hMSCs). CYP27B1 expression and cellular 1,25(OH)2D3 production were further potentiated by OA in cells at mature osteogenic stages. Notably, our study suggested that the osteogenic actions of OA were CYP27B1 dependent. In summary, the bone protective effects of OA were associated with the induction of CYP27B1 activity and expression in bone tissues and osteoblastic lineages. Hence, OA might be a potential approach for management of age-related bone loss.

Hypoparathyroidism and pseudohypoparathyroidism in pregnancy: an Italian retrospective observational study

Background

Hypoparathyroidism (HypoPT) or pseudo-hypoparathyroidism (pseudo-HypoPT) during pregnancy may cause maternal and fetal/neonatal complications. In this regard, only a few case reports or case series of pregnant or lactating women have been published. The purpose of this study was to describe clinical and biochemical course, pharmacological management, and potential adverse events during pregnancy and post-partum in pregnant women with HypoPT or pseudo-HypoPT. This was a retrospective, observational, multicenter, study involving nine Italian referral centers for endocrine diseases affiliated with the Italian Society of Endocrinology and involved in “Hypoparathyroidism Working Group”.

Results

This study identified a cohort of 28 women (followed between 2005 and 2018) with HypoPT (n = 25, 84% postsurgical, 16% idiopathic/autoimmune) and pseudo-HypoPT (n = 3). In HypoPT women, the mean calcium carbonate dose tended to increase gradually from the first to third trimester (+ 12.6%) in pregnancy. This average increase in the third trimester was significantly greater compared to the pre-pregnancy period (p value = 0.03). However, analyzing the individual cases, in 44% the mean calcium dosage remained unchanged throughout gestation. Mean calcitriol doses tended to increase during pregnancy, with a statistically significant increase between the third trimester and the pre-pregnancy period (p value = 0.02). Nevertheless, analyzing the individual cases, in the third trimester most women with HypoPT (64%) maintained the same dosage of calcitriol compared to the first trimester. Both mean calcium carbonate and calcitriol doses tended to decrease from the third trimester to the post-partum six months. Most identified women (~ 70%) did not display maternal complications and (~ 90%) maintained mean serum albumin-corrected total calcium levels within the low-to-mid normal reference range (8.5 ± 0.8 mg/dl) during pregnancy. The main complications related to pregnancy period included: preterm birth (n = 3 HypoPT women), and history of miscarriages (n = 6 HypoPT women and n = 2 pseudo-HypoPT women).

Conclusion

This study shows that mean serum albumin-corrected total calcium levels were carefully monitored during pregnancy and post-pregnancy, with limited evaluation of other biochemical parameters, such as serum phosphate, 24 h urinary calcium, 25-OH vitamin D, and creatinine clearance. To avoid complications in mothers affected by (HypoPT) or (pseudo-HypoPT) and offspring, intense biochemical, clinical and pharmacological monitoring during pregnancy and breastfeeding is highly recommended.

Maternal and fetal vitamin D and their roles in mineral homeostasis and fetal bone development

During pregnancy, female physiology adapts to meet the additional mineral demands of the developing fetus. Meanwhile, the fetus actively transports minerals across the placenta and maintains high circulating levels to mineralize the rapidly developing skeleton. Most of this mineral is accreted during the last trimester, including 30 g of calcium, 20 g of phosphate and 0.8 g of magnesium. Given the dependence of calcium homeostasis on vitamin D and calcitriol in the adult and child, it may be expected that vitamin D sufficiency would be even more critical during pregnancy and fetal development. However, the pregnant mother and fetus appear to meet their mineral needs independent of vitamin D. Adaptations in maternal mineral and bone metabolism during pregnancy appear to be invoked independent of maternal vitamin D, while fetal mineral metabolism and skeletal development appear to be protected from vitamin D deficiency and genetic disorders of vitamin D physiology. This review discusses key data from both animal models and human studies to address our current knowledge on the role of vitamin D and calcitriol during pregnancy and fetal development.

Mineral and bone physiology in the foetus, preterm and full-term neonates

Mother is the major source of minerals in foetal life with placenta actively transporting against a concentration and electrochemical gradient. The foetal serum mineral concentration is thereby higher as compared to maternal values, which possibly help in its rapid accretion in developing bones and for counteracting postnatal fall in calcium levels at birth. Parathyroid hormone related peptide (PTHrP) and parathyroid hormone (PTH) play a major role in mineral physiology during foetal life with hormones like calcitriol, calcitonin, FGF-23 and sex steroids having minimal role. PTHrP and PTH also play a major role in endochondral bone formation and mineralization of skeleton. At the birth, as the cord is clamped, there is loss of active transport of minerals through placenta and the neonate has to rely on enteral intake of minerals to meet the demands of growing bones and metabolisms. The calcium levels fall after birth, reaching a nadir at 24-48 h and gradually rise to adult values over several days, probably resulting from a fall in PTHrP levels and hyporesponsiveness of parathyroid glands. As PTH and calcitriol levels increase postnatally, there is a rise in calcium levels with maturation in functioning of kidneys and intestines. However, there may be significant delay in intestinal maturation in preterm infants along with an increased demand for mineral accretion, which predispose them to osteopenia of prematurity.

Physiologic and pathophysiologic roles of extra renal CYP27b1: Case report and review

Although the kidney was initially thought to be the sole organ responsible for the production of 1,25(OH)₂D via the enzyme CYP27b1, it is now appreciated that the expression of CYP27b1 in tissues other than the kidney is wide spread. However, the kidney is the major source for circulating 1,25(OH)₂D. Only in certain granulomatous diseases such as sarcoidosis does the extra renal tissue produce sufficient 1,25(OH)₂D to contribute to the circulating levels, generally associated with hypercalcemia, as illustrated by the case report preceding the review. Therefore the expression of CYP27b1 outside the kidney under normal circumstances begs the question why, and in particular whether the extra renal production of 1,25(OH)₂D has physiologic importance. In this chapter this question will be discussed. First we discuss the sites for extra renal 1,25(OH)₂D production. This is followed by a discussion of the regulation of CYP27b1 expression and activity in extra renal tissues, pointing out that such regulation is tissue specific and different from that of CYP27b1 in the kidney. Finally the physiologic significance of extra renal 1,25(OH)₂D₃ production is examined, with special focus on the role of CYP27b1 in regulation of cellular proliferation and differentiation, hormone secretion, and immune function. At this point the data do not clearly demonstrate an essential role for CYP27b1 expression in any tissue outside the kidney, but several examples pointing in this direction are provided. With the availability of the mouse enabling tissue specific deletion of CYP27b1, the role of extra renal CYP27b1 expression in normal and pathologic states can now be addressed definitively.

The importance of vitamin D in maternal and child health: a global perspective

Vitamin D and calcium are important nutrients for skeletal growth and bone health. Children and pregnant women are particularly vulnerable to 25-hydroxy vitamin D deficiency (VDD). VDD, with or without dietary calcium deficiency, can lead to nutritional rickets (NR), osteomalacia, and disturbances in calcium homeostasis. Multiple studies have linked VDD to adverse health outcomes in both children and pregnant women that extend beyond bone health. VDD remains an important global public health concern, and an important differentiation must be made between the impact of VDD on children and adults. Reports of increased incidence of NR continue to emerge. NR is an entirely preventable condition, which could be eradicated in infants and children worldwide with adequate vitamin D and calcium supplementation. The desire and necessity to put in place systems for preventing this potentially devastating pediatric disease should not elicit dispute. VDD and NR are global public health issues that require a collaborative, multi-level approach for the implementation of feasible preventative strategies. This review highlights the history, risk factors, and controversies related to VDD during pregnancy and childhood with a particular focus on global NR prevention.

Maternal depression attenuates newborn vitamin D concentrations in winter-spring: a prospective population-based study

We aimed to investigate whether the newborns of mothers with maternal depression (MD) had lower vitamin D levels than newborns of non-MD (NMD) mothers and identify the potential mechanism underlying this association. Maternal depressive symptoms in late pregnancy and concentrations of cord blood 25 hydroxyvitamin D (25(OH)D) were measured in 1491 mother-infant pairs. Data on maternal sociodemographic characteristics, health status, lifestyle and birth outcomes were prospectively collected. For infants born in winter-spring, the infants of MD mothers had significantly reduced concentrations of 25(OH) D (adjusted β = −3.51 nmol/L; 95% CI: −6.19, −0.84; P = 0.010) and lower birth weight (3267 ± 470 g vs 3348 ± 598 g, F = 4.64, P = 0.031), compared with the infants of NMD mothers. A significant, inverse linear relationship was noted between maternal depression scores and the concentration of 25(OH)D for infants born in winter-spring (adjusted β = −0.158; 95% CI: −0.259, −0.057). The significant, inverse linear relationship between maternal depression scores and fetomaternal ratios of 25(OH) D was also observed among the infants born in winter-spring (adjusted β = −0.005; 95% CI: −0.008, −0.003). MD appears to significantly attenuate the vitamin D concentrations and birth weight of infants born in winter-spring. A decreased fetomaternal ratio of 25(OH)D might be involved in this biological pathway.

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.

Current concepts in perinatal mineral metabolism

The serum levels of calcium (Ca) and phosphate are maintained higher in the fetus than in the pregnant mother, especially in late gestation, to meet the demands of fetal bone development. In order to maintain this fetal stage-specific mineral homeostasis, the placenta plays a critical role through active transcellular mineral transport. Although the molecular mechanism of transplacental Ca transport has been well studied, little is known about the transport mechanism of phosphate and magnesium. Maternal mineral homeostasis is also altered during pregnancy to supply minerals to the fetus. In the lactating mother, osteocytic osteolysis is suggested to be involved in the supply of minerals to the baby. The levels of some calcitropic and phosphotropic (Ca- and phosphate-regulating, respectively) hormones in the fetus are also different from those in the adult. The PTH level in the fetus is lower than that in the mother and nonpregnant adult. It is suggested, however, that low fetal PTH plays an important role in fetal mineral metabolism. The concentration of PTHrP in the fetus is much higher than that of PTH and plays a critical role in perinatal Ca homeostasis. Uncovering the molecular mechanisms for fetal stage-specific mineral metabolism will lead to better management of perinatal patients with mineral abnormalities.

Cross-sectional study of serum parathyroid hormone level in high-risk pregnancies as compared to nonpregnant control

OBJECTIVES

To note the value of serum parathyroid hormone (PTH) levels in normal and high-risk pregnancies (HRP) in patients attending antenatal visits at All India Institute of Medical Sciences (AIIMS).

MATERIALS AND METHODS

This is a cross-sectional study where a total of 282 patients attending Gynecology Outpatient Department at AIIMS, New Delhi were recruited. Among the 282 subjects, 251 were pregnant, and 31 were controls. The serum was tested for serum PTH levels using Beckman coulter access 2 immunoassay.

RESULTS

The median value of PTH level in pregnant women was 31.6 pg/ml with range being 0.8-505.5 pg/ml in contrast to 45.9 pg/ml with range being 19-102.7 pg/ml in nonpregnant female. This difference was statistically significant (P = 0.0012). There was no significant difference in median level of PTH in different age group. Although the median PTH levels were lower in second trimester (25.25 pg/ml) than in first trimester (35.5 pg/ml) and in third trimester (32.4 pg/ml), the difference was not statistically significant. There was no significant difference in PTH level in HRP (median value - 31.6 pg/ml) as compared to low-risk pregnancies (31.5 pg/ml).

CONCLUSION

Serum PTH levels are significantly lower during pregnancy as compared to nonpregnant state. However, age, parity, and HRP did not alter PTH level during pregnancy.

A review of the impact of dietary intakes in human pregnancy on infant birthweight

Studies assessing maternal dietary intakes and the relationship with birthweight are inconsistent, thus attempting to draw inferences on the role of maternal nutrition in determining the fetal growth trajectory is difficult. The aim of this review is to provide updated evidence from epidemiological and randomized controlled trials on the impact of dietary and supplemental intakes of omega-3 long-chain polyunsaturated fatty acids, zinc, folate, iron, calcium, and vitamin D, as well as dietary patterns, on infant birthweight. A comprehensive review of the literature was undertaken via the electronic databases Pubmed, Cochrane Library, and Medline. Included articles were those published in English, in scholarly journals, and which provided information about diet and nutrition during pregnancy and infant birthweight. There is insufficient evidence for omega-3 fatty acid supplements’ ability to reduce risk of low birthweight (LBW), and more robust evidence from studies supplementing with zinc, calcium, and/or vitamin D needs to be established. Iron supplementation appears to increase birthweight, particularly when there are increases in maternal hemoglobin concentrations in the third trimester. There is limited evidence supporting the use of folic acid supplements to reduce the risk for LBW; however, supplementation may increase birthweight by ~130 g. Consumption of whole foods such as fruit, vegetables, low-fat dairy, and lean meats throughout pregnancy appears beneficial for appropriate birthweight. Intervention studies with an understanding of optimal dietary patterns may provide promising results for both maternal and perinatal health. Outcomes from these studies will help determine what sort of dietary advice could be promoted to women during pregnancy in order to promote the best health for themselves and their baby.

Bone development and mineral homeostasis in the fetus and neonate: roles of the calciotropic and phosphotropic hormones

Mineral and bone metabolism are regulated differently in utero compared with the adult. The fetal kidneys, intestines, and skeleton are not dominant sources of mineral supply for the fetus. Instead, the placenta meets the fetal need for mineral by actively transporting calcium, phosphorus, and magnesium from the maternal circulation. These minerals are maintained in the fetal circulation at higher concentrations than in the mother and normal adult, and such high levels appear necessary for the developing skeleton to accrete a normal amount of mineral by term. Parathyroid hormone (PTH) and calcitriol circulate at low concentrations in the fetal circulation. Fetal bone development and the regulation of serum minerals are critically dependent on PTH and PTH-related protein, but not vitamin D/calcitriol, fibroblast growth factor-23, calcitonin, or the sex steroids. After birth, the serum calcium falls and phosphorus rises before gradually reaching adult values over the subsequent 24-48 h. The intestines are the main source of mineral for the neonate, while the kidneys reabsorb mineral, and bone turnover contributes mineral to the circulation. This switch in the regulation of mineral homeostasis is triggered by loss of the placenta and a postnatal fall in serum calcium, and is followed in sequence by a rise in PTH and then an increase in calcitriol. Intestinal calcium absorption is initially a passive process facilitated by lactose, but later becomes active and calcitriol-dependent. However, calcitriol's role can be bypassed by increasing the calcium content of the diet, or by parenteral administration of calcium.

Establishment of a seafood index to assess the seafood consumption in pregnant women

Background

Seafood (fish and shellfish) is an excellent source of several essential nutrients for pregnant and lactating women. A short food frequency questionnaire (FFQ) that can be used to quantitatively estimate seafood consumption would be a valuable tool to assess seafood consumption in this group. Currently there is no such validated FFQ in Norway.

Objective

The objective of this study was to establish and validate a seafood index from a seafood FFQ against blood biomarkers (the omega-3 index, the omega-3 HUFA score, and serum 25OH vitamin D).

Design

We assessed maternal seafood consumption during the 28th gestation week in healthy Norwegian women (n=54) with a seafood FFQ. A seafood index was developed to convert ordinal frequency data from the FFQ into numerical scale data. The following blood biomarkers were used as a validation method: omega-3 index, omega-3 HUFA score, and the serum 25OH vitamin D.

Results

The reported frequency of seafood as dinner and as spread was strongly correlated with the estimated frequencies of seafood as dinner and as spread. This indicated that the seafood index is a valuable tool to aggregate reported frequencies from the seafood FFQ. The seafood index composed of the frequency of seafood consumption and intake of omega-3 supplements, termed the total seafood index, correlated positively with the omega-3 index, omega-3 HUFA score, and 25OH vitamin D.

Conclusion

We established and validated a seafood index from a seafood FFQ. The developed seafood index can be used when studying health effects of seafood consumption in large populations. This seafood FFQ captures seafood consumption and omega-3 supplement intake considerably well in a group of pregnant women.

Vitamin D supplementation is associated with higher serum 25OHD in Asian and White infants living in Vancouver, Canada

To prevent rickets, the Health Canada and the American Academy of Pediatrics recommend that breastfed infants receive a daily vitamin D supplement of 10 μg d(-1) . Compliance with this recommendation is variable and its effect on infant vitamin D status is unclear. We measured serum 25-hydroxyvitamin D (25OHD) in Asian immigrant (n=28) and White (n=37) mothers and their infants aged 2-4 months living in Vancouver (49°N). Mothers completed health and demographic questionnaires. All subjects were term infants who were primarily breastfed. Analysis of variance, χ(2) , multiple regression and logistic regression analysis were performed as appropriate. Mean 25OHD of the infants was 31 (95% confidence interval 28-34) ng mL(-1) . Only two infants had a 25OHD concentration indicative of deficiency, <10 ng mL(-1) . Of the infants, 14% (n=9) and 49% (n=32) were vitamin D insufficient based on two commonly used cut-offs of 20 and 30 ng mL(-1) , respectively. Fifty-eight (89%) infants had been given a vitamin D supplement. Mean 25OHD was 9.4 ng mL(-1) higher in infants consuming ≥10 μg d(-1) of vitamin D from supplements vs. those consuming less (P=0.003). Mother's 25OHD, season, skin colour or ethnicity (Asian vs. White) did not influence infant 25OHD. The infants in our study, most of whom received vitamin D supplements, were generally protected against low 25OHD. The study was limited by sample size and the nature of the cross-sectional study design.

Extrarenal expression of the 25-hydroxyvitamin D-1-hydroxylase

Like the vitamin D receptor (VDR), the CYP27B1-hydroxylase is expressed widely in human tissues. This expression profile establishes the potential for interaction of the VDR with the product of the CYP27B1, 1,25-dihydroxyvitamin D (1,25-(OH)(2)D), in either an intracrine or paracrine mode. This expansive expression profile also suggests that the local production and action of 1,25-(OH)(2)D to regulate VDR-directed gene expression may be similarly wide-ranging and distinct from what occurs in the kidney; the proximal renal tubular epithelial cell is the richest source of the CYP27B1 and the site for production of 1,25-(OH)(2)D destined to function as a hormone. Existence of the CYP27B1 at extrarenal sites has been widely documented, although the functional impact of the enzyme in these tissues has yet to be fully demonstrated. Two notable exceptions are the disease-activated macrophage (e.g., in sarcoidosis or tuberculosis) and the placenta. These two tissues are capable of generating enough 1,25-(OH)(2)D so as to be detectable in the general circulation. As such, this review will focus on CYP27B1 expression only at these two sites, theorizing that 1,25-(OH)(2)D production at these sites is for the purpose of local immunoregulatory function, not for controlling calcium balance in the host or the fetus.

Vitamin D supplementation during pregnancy: safety considerations in the design and interpretation of clinical trials

Maternal-child health benefits of optimizing vitamin D status during pregnancy may include a reduced risk of pre-eclampsia, improved fetal growth and beneficial effects on infant immune function. These hypotheses require evaluation by randomized controlled antenatal vitamin D supplementation trials using doses that are high enough to elevate serum 25-hydroxyvitamin D concentrations into the range believed to be associated with improved health outcomes. Such doses may be considerably higher than the current recommended dietary allowance (600 IU day(-1)) or standard prenatal supplement dose (400 IU day(-1)), and may even be higher than the tolerable upper intake level (4000 IU day(-1)) advised by the Institute of Medicine (2010). A critical review of the published literature yielded limited data regarding the safety of antenatal vitamin D regimens. There have been no published reports of the teratogenic effects of vitamin D on humans. Some animal studies have suggested the potential for dose-dependent fetal toxicities (for example, growth impairment, skeletal malformations and cardiovascular anomalies), but the relevance of these observations to humans is unknown. Antenatal vitamin D supplementation trials should incorporate a range of methods for objectively establishing maternal and fetal safety, and aim to identify the lowest doses of vitamin D required to achieve target outcomes.

Major translocation of calcium upon epidermal barrier insult: imaging and quantification via FLIM/Fourier vector analysis

Calcium controls an array of key events in keratinocytes and epidermis: localized changes in Ca(2+) concentrations and their regulation are therefore especially important to assess when observing epidermal barrier homeostasis and repair, neonatal barrier establishment, in differentiation, signaling, cell adhesion, and in various pathological states. Yet, tissue- and cellular Ca(2+) concentrations in physiologic and diseased states are only partially known, and difficult to measure. Prior observations on the Ca(2+) distribution in skin were based on Ca(2+) precipitation followed by electron microscopy, or proton-induced X-ray emission. Neither cellular and/or subcellular localization could be determined through these approaches. In cells in vitro, fluorescent dyes have been used extensively for ratiometric measurements of static and dynamic Ca(2+) concentrations, also assessing organelle Ca(2+) concentrations. For lack of better methods, these findings together build the basis for the current view of the role of Ca(2+) in epidermis, their limitations notwithstanding. Here we report a method using Calcium Green 5N as the calcium sensor and the phasor-plot approach to separate raw lifetime components. Thus, fluorescence lifetime imaging (FLIM) enables us to quantitatively assess and visualize dynamic changes of Ca(2+) at light-microscopic resolution in ex vivo biopsies of unfixed epidermis, in close to in vivo conditions. Comparing undisturbed epidermis with epidermis following a barrier insult revealed major shifts, and more importantly, a mobilization of high amounts of Ca(2+) shortly following barrier disruption, from intracellular stores. These results partially contradict the conventional view, where barrier insults abrogate a Ca(2+) gradient towards the stratum granulosum. Ca(2+) FLIM overcomes prior limitations in the observation of epidermal Ca(2+) dynamics, and will allow further insights into basic epidermal physiology.

Low vitamin D status in mother-newborn pairs in Greece

Adequate vitamin D status during pregnancy is crucial to assure normal fetal skeletal growth and to provide the vitamin D needed for infants' stores. To determine the actual situation in Greece, we evaluated serum 25-hydroxyvitamin D (25[OH]D), calcium (Ca), phosphorus (P), alkaline phosphatase (ALP), parathyroid hormone (PTH), osteocalcin (OC), and calcitonin (CT) concentrations in 123 healthy mother-newborn pairs recruited from a public hospital of the sunny Athenian region. Blood samples were obtained from pregnant women at term and their neonates (cord blood). The study was conducted between June 2003 and May 2004. None of the mothers has been prescribed vitamin D supplements. Maternal 25(OH)D levels (16.4 [11-21.1] ng/mL) were significantly lower than umbilical venous blood concentrations (20.4 [13.9-30.4] ng/mL) (P < 0.001). A strong correlation was observed between maternal and infant 25(OH)D concentrations (r = 0.626, P < 0.001). Twenty-four (19.5%) mothers and 10 (8.1%) neonates had 25(OH)D <10 ng/mL. Pregnant women who delivered in summer and autumn reported higher levels of 25(OH)D (18.9 [12.9-23.3] ng/mL) than those who delivered in winter and spring (14.6 [10.1-18.5] ng/mL) (P = 0.006). Mothers with a darker phototype had lower levels of serum 25(OH) D than those with a fair phototype (P = 0.023). Umbilical venous blood Ca, P, OC, and CT levels were significantly higher than maternal venous blood levels (P < 0.001). PTH umbilical levels were lower than maternal levels (P < 0.001). Apparently, the abundant sunlight exposure in Athens is not sufficient to prevent hypovitaminosis D. Pregnant women should be prescribed vitamin D supplementations, and the scientific community should consider vitamin D supplementation of foods.

The vitamin D receptor is not required for fetal mineral homeostasis or for the regulation of placental calcium transfer in mice

We utilized a vitamin D receptor (VDR) gene knockout model to study the effects of maternal and fetal absence of VDR on maternal fertility, fetal-placental calcium transfer, and fetal mineral homoeostasis. Vdr null mice were profoundly hypocalcemic, conceived infrequently, and had significantly fewer viable fetuses in utero that were also of lower body weight. Supplementation of a calcium-enriched diet increased the rate of conception in Vdr nulls but did not normalize the number or weight of viable fetuses. Among offspring of heterozygous (Vdr(+/-)) mothers (wild type, Vdr(+/-), and Vdr null fetuses), there was no alteration in serum Ca, P, or Mg, parathyroid hormone, placental (45)Ca transfer, Ca and Mg content of the fetal skeleton, and morphology and gene expression in the fetal growth plates. Vdr null fetuses did have threefold increased 1,25-dihydroxyvitamin D levels accompanied by increased 1alpha-hydroxylase mRNA in kidney but not placenta; a small increase was also noted in placental expression of parathyroid hormone-related protein (PTHrP). Among offspring of Vdr null mothers, Vdr(+/-) and Vdr null fetuses had normal ionized calcium levels and a skeletal ash weight that was appropriate to the lower body weight. Thus our findings indicate that VDR is not required by fetal mice to regulate placental calcium transfer, circulating mineral levels, and skeletal mineralization. Absence of maternal VDR has global effects on fetal growth that were partly dependent on maternal calcium intake, but absence of maternal VDR did not specifically affect fetal mineral homeostasis.

Hyperparathyroidism and pregnancy: case report and review

In pregnant women with symptomatic hyperparathyroidism, parathyroidectomy should be undertaken during the second trimester. We feel that the woman who is initially diagnosed well into the third trimester should be treated medically unless the hypercalcemia worsens or other complications occur. Since the treatment of asymptomatic hyperparathyroidism itself is controversial, it is even more difficult to define the treatment plan for an asymptomatic pregnant patient who has primary hyperparathyroidism. However, a recent consensus panel recommended that young patients with asymptomatic hyperparathyroidism be treated surgically. Accordingly, we believe that the asymptomatic pregnant patient should also be treated surgically, preferably in the second trimester. Whether a patient is treated medically or surgically in these situations, the pregnancy should be considered high-risk. The neonate should be monitored carefully for signs of hypocalcemia or impending tetany. If the mother is treated medically to term (or if spontaneous or elective abortion occurs), the mother should be monitored for hyperparathyroid crisis postpartum. Sudden worsening of hypercalcemia can result from the loss of the placenta (active placental calcium transport may be somewhat protective) and dehydration. Finally, every effort should be made to make the definitive diagnosis early in pregnancy in order to initiate optimal management. The diagnosis should be suspected during pregnancy if the following conditions exist: appropriate clinical signs or symptoms (especially nephrolithiasis or pancreatitis), hyperemesis beyond the first trimester, history of recurrent spontaneous abortions/stillbirths or neonatal deaths, neonatal hypocalcemia or tetany, or a total serum calcium concentration greater than 10.1 mg/dL (2.52 mmol/L) or 8.8 mg/dL (2.2 mmol/L) during the second or third trimester, respectively.

Evidence that calcitonin plays a role in the postnatal increase of serum 1 alpha,25-dihydroxyvitamin D

To investigate the changes in the 1 alpha,25-dihydroxyvitamin D [1,25(OH)2D] level and the role of parathyroid hormone (PTH) and calcitonin (CT) during the early neonatal periods, we measured 1,25(OH)2D, 25-hydroxyvitamin D [25(OH)D], PTH specific for mid-regions (mPTH) and urinary cAMP (UcAMP) to evaluate the renal tubular responsiveness to intrinsic PTH and CT, as well as serum Ca and P in 28 mothers at term delivery and in their babies at birth and 5 days of age. Cord serum 1,25(OH)2D levels were low (28.8 +/- 9.2 pg/ml, mean +/- SD), while maternal serum 1,25(OH)2D levels were high (62.2 +/- 22.6 pg/ml). The low 1,25(OH)2D value increased 2.5 times (62.2 +/- 22.6 pg/ml) in 5-day-old infants, reaching a high normal adult value, concomitant with the increases in mPTH and urinary cAMP/creatinine ratio (UcAMP/Cr). The correlations between 1,25(OH)2D and UcAMP/Cr, and 1,25(OH)2D and mPTH in all paired samples of babies at birth and at 5 days of age were r = 0.456, n = 50, P less than 0.01 and r = 0.341, n = 50, P less than 0.05, respectively. These data suggest that the parathyroid activation after birth is a major factor in the rapid 1,25(OH)2D increment at that time. CT levels were high in all paired samples and in 5-day-old infants. CT vs 1,25(OH)2D showed a significant correlation (r = 0.473, P less than 0.05, n = 24) as well as the relative increase of 1,25(OH)2D (delta pg/ml) after birth vs CT at age 5 days (r = 0.537, P less than 0.01, n = 24).(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochemical bioassay of parathyroid hormone in maternal and cord blood

Parathyroid hormone and calcium were measured in plasma taken from pregnant women at term and from the umbilical veins of their infants at birth. Three assays were used to measure parathyroid hormone, a cytochemical bioassay of bioactivity and two immunoradiometric assays, one specific for the amino terminus, the other specific for the carboxy terminus of the parathyroid hormone molecule. Plasma calcium was significantly higher in the infants than in the mothers. Maternal parathyroid hormone bioactivity and the amino terminus were both slightly raised, but the carboxy terminus value was normal; these findings supported the view that late pregnancy is a time of mild physiological hyperparathyroidism. In the infants, the amino terminus was undetectable and the carboxy terminus was either undetectable or towards the lower end of the normal range: bioactivity of parathyroid hormone was considerably raised and was related to the gradient of calcium across the placenta. This suggests that the parathyroid glands are not suppressed during fetal life and that they may play an important part in the maintenance of high fetal plasma calcium concentrations.

Control of vitamin D metabolism in preterm infants: feto-maternal relationships

To assess the relationship between maternal and fetal mineral homeostasis, serum calcium, magnesium, inorganic phosphate, parathyroid hormone, and vitamin D metabolite concentrations in venous cord sera from 15 preterm singletons and 3 twin pairs were compared with the levels found in maternal sera. Cord calcium, magnesium, and phosphorus levels were significantly higher than the respective levels in maternal samples. There was a significant relationship between the two compartments for all three analyses. Cord serum 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D, and 1,25-dihydroxyvitamin D levels were significantly lower than those observed for the mothers. Association of the cord concentration with that of the mothers was observed only for the first two metabolites. There was no relationship between the maternal 1,25-dihydroxyvitamin D levels and gestational age, calcium, magnesium, inorganic phosphate, or 25-hydroxyvitamin D. Cord 1,25-dihydroxyvitamin D correlated significantly only with cord calcium levels. Immunoreactive parathyroid hormone levels were within normal limits both in cord and maternal samples. Our data suggest that after 31 weeks of gestation: (1) calcium, magnesium, and inorganic phosphate cross the placental barrier against a concentration gradient; (2) the fetus depends on the maternal supply for 25-hydroxyvitamin D and 24,25 dihydroxyvitamin D; (3) the feto-placental unit synthesizes 1,25-dihydroxyvitamin D according to fetal needs.

Calcitonin: regional distribution of the hormone and its binding sites in the human brain and pituitary

Immunoreactive calcitonin (CT), indistinguishable from human CT-(1-32) and its sulfoxide, has been identified in extracts of the hypothalamus, the pituitary, and the thyroid obtained from human subjects at autopsy. DCT concentrations were highest in a region encompassing the posterior hypothalamus, the median eminence, and the pituitary; intermediate in the substantia nigra, the anterior hypothalamus, the globus pallidus, and the inferior colliculus; and low in the caudate nucleus, the hippocampus, the amygdala, and the cerebral and cerebellar cortices. Specific CT binding measured with 125I-labeled salmon CT was highest in homogenates of the posterior hypothalamus and the median eminence, shown to contain the highest concentrations of endogenous CT in the brain; CT binding was less than 12% of hypothalamic binding in all of the other regions of the brain examined and was negligible in the pituitary. Half-maximal binding was achieved with 0.1 nM nonradioactive salmon CT-(1-32), and the binding was directed to structural or conformational sites, or both, in the COOH-terminal half of salmon CT. The rank order of the inhibition of the binding by CT from different species and analogues of the human hormone was the same as in receptors on a human lymphoid cell line (Moran, J., Hunziker, W. & Fischer, J. A. (1978) Proc. Natl. Acad. Sci. USA 75, 3984-3988). The functional role of CT and of its binding sites in the brain remains to be elucidated.

Interrelations of calcium-regulating hormones during normal pregnancy

Profound changes in calcium metabolism occur during pregnancy. The mother has to make available extra calcium for fetal requirements while ensuring that her plasma and bone calcium concentrations are satisfactorily maintained. In a cross-sectional study plasma concentrations of the major calcium-regulating hormones--namely, calcitonin, parathyroid hormone, 25-hydroxyvitamin D (25-OHD), and 1,25-dihydroxyvitamin D (1,25-(OH)2D)--were measured to establish their interrelations during normal pregnancy. The major changes observed were increases in the circulating concentrations of 1,25-(OH)2D and calcitonin. Concentrations of parathyroid hormone and 25-OHD remained within the normal range. The increased concentrations of 1,25-(OH)2D enable the increased physiological need for calcium to be met by enhancing intestinal absorption of this element. The simultaneous rise in calcitonin opposes the bone-resorbing activities of 1,25-(OH)2D, thereby protecting the integrity of the maternal skeleton. Maternal calcium homeostasis is thus maintained yet the requirements of the fetus are fulfilled.