Spectrum and natural history of congenital hyperparathyroidism secondary to maternal hypocalcemia

Pregnancy, delivery and neonatal outcomes among women with hypoparathyroidism-A population-based study

OBJECTIVE

Data are inconclusive regarding pregnancy complications associated with maternal chronic hypoparathyroidism. Therefore, we aimed to compare pregnancy, delivery and neonatal outcomes in patients affected by chronic hypoparathyroidism to those without chronic hypoparathyroidism.

DESIGN

A retrospective population-based study utilising data from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (HCUP-NIS) database over 11 years from 2004 to 2014 inclusively. Multivariate logistic regression was used to control for confounders.

PATIENTS

Patients with chronic hypoparathyroidism compared with those without.

MEASUREMENTS

Obstetric and neonatal outcomes.

RESULTS

We identified 204 pregnancies in mothers with chronic hypoparathyroidism and 9,096,584 pregnancies without chronic hypoparathyroidism. After adjusting for age, insurance plan type, obesity, chronic hypertension, thyroid disease, pregestational diabetes mellitus, and previous caesarean section, patients in the hypoparathyroidism group, compared with those without hypoparathyroidism, were found to have an increased rate of preterm birth (<37 weeks) (19.1% vs. 7.2%, aOR: 2.49, 95% confidence interval [CI]: 1.74-3.54, p < 0.0001, respectively); and blood transfusions (4.9% vs. 1.0%, aOR: 4.07, 95% CI: 2.15-7.73, p < -0.0001). Neonates to mothers with chronic hypoparathyroidism had a higher rate of congenital anomalies (4.4% vs. 0.4%, aOR: 6.50, 95% CI: 3.31-12.75, p < 0.0001), with comparable rates of small-for-gestational-age neonates and intrauterine foetal death.

CONCLUSION

This is the largest study of chronic hypoparathyroidism in pregnancy to date. We found significant increases in the rates of preterm birth, blood transfusions and congenital anomalies in chronic hypoparathyroidism. Our findings highlight the importance of identifying chronic hypoparathyroidism as a risk factor for pregnancy and neonatal complications, although it remains unknown if maintaining calcium in the target range will mitigate these risks.

Quantifying calcium changes in the fetal spine using quantitative susceptibility mapping as extracted from STAGE imaging

OBJECTIVES

To evaluate calcium deposition in the fetal spine in vivo during the second and third trimesters using quantitative susceptibility mapping (QSM).

METHODS

Fifty-four pregnant women in their second and third trimesters underwent a 2D multi-echo STrategically Acquired Gradient Echo (STAGE) MR imaging protocol at 3T covering the fetal spine. The first echo data was used for QSM processing. A linear regression model was used to assess the correlation between magnetic susceptibility and gestational age (GA). A paired sample t-test was used to compare the consistency of QSM measurements from each sequence.

RESULTS

The magnetic susceptibility of the fetal spine decreased linearly with advancing GA, with a slope of -52.3 parts per billion (ppb)/week and a Pearson correlation coefficient (r) of 0.83 (p < 0.001). In 37 subjects for whom the STAGE local QSM data were available from both flip angles, the average magnetic susceptibility values were -1111 ± 278 ppb and -1081 ± 262 ppb for FA = 8° and FA = 40°, respectively. These means were not statistically different according to a paired sample t-test (p = 0.156).

CONCLUSIONS

QSM is a reliable technique for evaluating calcium deposition and bone mineral density of fetal vertebrae. Our results demonstrate an increase in fetal calcium levels as a function of GA. These measures might be able to provide reference values for calcium content in the fetal spine during the second and third trimesters.

KEY POINTS

• Calcium deposition and mineralization in the fetal spine, evaluated by vertebral magnetic susceptibility, increased with advancing gestational age. • Our results provide reference values for calcium content in the fetal spine during the second and third trimesters.

Hypoparathyroidism in Pregnancy and Lactation: Current Approach to Diagnosis and Management

Background: Hypoparathyroidism is an uncommon endocrine disorder. During pregnancy, multiple changes occur in the calcium-regulating hormones, which may affect the requirements of calcium and active vitamin D during pregnancy in patients with hypoparathyroidism. Close monitoring of serum calcium during pregnancy and lactation is ideal in order to optimize maternal and fetal outcomes. In this review, we describe calcium homeostasis during pregnancy in euparathyroid individuals and also review the diagnosis and management of hypoparathyroidism during pregnancy and lactation. Methods: We searched the MEDLINE, CINAHL, EMBASE, and Google scholar databases from 1 January 1990 to 31 December 2020. Case reports, case series, book chapters, and clinical guidelines were included in this review. Conclusions: During pregnancy, rises in 1,25-dihydroxyvitamin D (1,25-(OH)2-D3) and PTH-related peptide result in suppression of PTH and enhanced calcium absorption from the bowel. In individuals with hypoparathyroidism, the requirements for calcium and active vitamin D may decrease. Close monitoring of serum calcium is advised in women with hypoparathyroidism with adjustment of the doses of calcium and active vitamin D to ensure that serum calcium is maintained in the low-normal to mid-normal reference range. Hyper- and hypocalcemia should be avoided in order to reduce the maternal and fetal complications of hypoparathyroidism during pregnancy and lactation. Standard of care therapy consisting of elemental calcium, active vitamin D, and vitamin D is safe during pregnancy.

Hypocalcemia After Thyroidectomy and Parathyroidectomy in a Pregnant Woman

Hypoparathyroidism during pregnancy is a very rare endocrine disorder. The majority of cases are postsurgical (75%). Managing pregnant or nursing women with hypoparathyroidism is challenging due to complications arising from either under- or overtreatment, including premature delivery or fetal death, abortion, stillbirth, perinatal death, and neonatal tetany. Specific adaptations are needed within each time period to meet the fetal, neonatal, and maternal calcium requirements. A systematic search was performed on PubMed using the search terms "pregnancy" and "hypoparathyroidism." Included were articles published in English between January 1, 1966, and January 1, 2018. We provide an overview of all published cases (n = 43) of hypoparathyroidism in pregnancy, including a case report of a 29-year-old pregnant woman who underwent a total thyroidectomy before her current pregnancy because of a therapy-resistantant Graves' disease. The procedure was complicated by postsurgical hypoparathyroidism. She carried out the pregnancy to term with minor complaints of paresthesia and muscle cramps. Furthermore, we discuss treatment, complications, and follow-up of hypoparathyroidism in pregnancy. Treatment of hypoparathyroidism in pregnancy should still be individualized, depending on the patient's complaints and serum levels of calcium, which should be maintained in the lower normal range of 2.15 to 2.55 mmol/l, according to the literature. We recommend monitoring calcium levels every 3 to 4 weeks throughout the pregnancy, within 1 week postpartum, and monthly during lactation to ensure normocalcemia.

Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

BACKGROUND

Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication.

EVIDENCE

A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describe the strength of the recommendation and the quality of supporting evidence.

PROCESS

Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus.

RESULTS

This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts.

CONCLUSION

Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required.

European Society of Endocrinology Clinical Guideline: Treatment of chronic hypoparathyroidism in adults

Hypoparathyroidism (HypoPT) is a rare (orphan) endocrine disease with low calcium and inappropriately low (insufficient) circulating parathyroid hormone levels, most often in adults secondary to thyroid surgery. Standard treatment is activated vitamin D analogues and calcium supplementation and not replacement of the lacking hormone, as in other hormonal deficiency states. The purpose of this guideline is to provide clinicians with guidance on the treatment and monitoring of chronic HypoPT in adults who do not have end-stage renal disease. We intend to draft a practical guideline, focusing on operationalized recommendations deemed to be useful in the daily management of patients. This guideline was developed and solely sponsored by The European Society of Endocrinology, supported by CBO (Dutch Institute for Health Care Improvement) and based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) principles as a methodological base. The clinical question on which the systematic literature search was based and for which available evidence was synthesized was: what is the best treatment for adult patients with chronic HypoPT? This systematic search found 1100 articles, which was reduced to 312 based on title and abstract. The working group assessed these for eligibility in more detail, and 32 full-text articles were assessed. For the final recommendations, other literature was also taken into account. Little evidence is available on how best to treat HypoPT. Data on quality of life and the risk of complications have just started to emerge, and clinical trials on how to optimize therapy are essentially non-existent. Most studies are of limited sample size, hampering firm conclusions. No studies are available relating target calcium levels with clinically relevant endpoints. Hence it is not possible to formulate recommendations based on strict evidence. This guideline is therefore mainly based on how patients are managed in clinical practice, as reported in small case series and based on the experiences of the authors.

Complications of vitamin D deficiency from the foetus to the infant: One cause, one prevention, but who's responsibility?

Calcium and phosphorus represent building material for bones. The supplier of these bone minerals is the hormone calcitriol, which originates from vitamin D, itself made by sunshine in human skin. Requirement for bone minerals is highest during phases of rapid growth, and no one grows faster than the foetus and the infant, making them particularly vulnerable. Deprivation of calcium, whether through low calcium intake or low vitamin D, leads to serious health consequences throughout life, such as hypocalcaemic seizures, dilated cardiomyopathy, skeletal myopathy, congenital and infantile rickets, and osteomalacia. These 5 conditions are often summarised as 'symptomatic vitamin D deficiency', are fully reversible but also fully preventable. However, the increasing prevalence of rickets and osteomalacia, and the deaths from hypocalcaemic cardiomyopathy, demand action from global health care providers. Clarification of medical and parental responsibilities is a prerequisite to deliver successful prevention programmes. The foetus and infant have the human right to be protected against harm, and vitamin D supplementation has the same public health priority as vaccinations.

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.

Endocrine emergencies

Several potentially fatal endocrine emergencies in relation to obstetrics and gynecology are discussed in the article. Rates of case fatality vary in different series, but range from 10% to 30%. Rapid recognition, prompt supportive care, and intervention likely maximize maternal and fetal outcomes.

Parathyroid and calcium metabolism disorders during pregnancy

Parathyroid disorders are not common among pregnant women, but harbor a significant morbidity and mortality potential if they remain unrecognized and untreated. The symptoms caused by abnormally low or high blood free calcium level are mostly non-specific in the initial stages, thus when recognized might pose a real danger. Here we will survey the alterations in calcium metabolism induced by pregnancy, and describe the clinical manifestations, diagnosis and treatment of parathyroid and other calcium metabolism disorders during pregnancy. The current literature on the impact of calcium and vitamin D deficiency during pregnancy will also be reviewed.

Primary hyperparathyroidism: an overview

Primary hyperparathyroidism is a common condition that affects 0.3% of the general population. Primary and tertiary care specialists can encounter patients with primary hyperparathyroidism, and prompt recognition and treatment can greatly reduce morbidity and mortality from this disease. In this paper we will review the basic physiology of calcium homeostasis and then consider genetic associations as well as common etiologies and presentations of primary hyperparathyroidism. We will consider emerging trends in detection and measurement of parathyroid hormone as well as available imaging modalities for the parathyroid glands. Surgical indications and approach will be reviewed as well as medical management of primary hyperparathyroidism with bisphosphonates and calcimimetics.

Hypercalcemia in children and adolescents

PURPOSE OF REVIEW

In this review, we define hypercalcemia levels, common causes for hypercalcemia in children, and treatment in order to aid the practicing pediatrician.

RECENT FINDINGS

One rare cause of hypercalcemia in the child is familial hypocalciuric hypercalcemia (also termed familial benign hypercalcemia). Mutations that inactivate the Ca-sensing receptor gene FHH have been described as an autosomal dominant disorder, but recently milder mutations in the CASR have been shown to cause hypercalcemia when homozygous.

SUMMARY

Normal serum levels of calcium are maintained through the interplay of parathyroid, renal, and skeletal factors. In this review, we have distinguished the neonate and infant from the older child and adolescent because the causes and clinical features of hypercalcemia can differ in these two age groups. However, the initial approach to the medical treatment of severe or symptomatic hypercalcemia is to increase the urinary excretion of calcium in both groups. In most cases, hypercalcemia is due to osteoclastic bone resorption, and agents that inhibit or destroy osteoclasts are, therefore, effective treatments. Parathyroid surgery, the conventional treatment for adults with symptomatic primary hyperparathyroidism, is recommended for all children with primary hyperparathyroidism.

Hyperparathyroidism secondary to maternal hypoparathyroidism and vitamin D deficiency: an uncommon cause of neonatal respiratory distress

A 4-day-old neonate presented with respiratory distress owing to chest wall deformity associated with metabolic bone disease. He was found to have congenital hyperparathyroidism and his mother was suffering from post-surgical hypoparathyroidism and vitamin D deficiency. The patient was given calcium lactate and maintenance doses of vitamin D. The respiratory distress subsided, the parathyroid hormone level returned to normal and by 4 weeks of age bone mineral content had improved. Congenital hyperparathyroidism should be considered in neonates presenting with respiratory distress and chest deformity.

Calcium metabolism in pregnancy and lactation

Homeostatic adaptation to maternal calcium metabolism is a prerequisite for optimal delivery of sufficient calcium to the fetus and neonate during pregnancy and lactation, respectively. This article outlines the major adaptations known to occur and the physiological regulators likely to be principally involved. Importantly, different adaptive responses are used in pregnancy and lactation. The rarity of calcium disorders in pregnancy underscores the successful implementation of these adaptations in most women. For those few women with either pre-existing or pregnancy-acquired disorders of calcium metabolism, a knowledge of normal physiology is essential to understand the implications for managing these disorders in pregnant women.

Effect of Chronic Ethanol Consumption on the Response of Parathyroid Hormone to Hypocalcemia in the Pregnant Rat

BACKGROUND

Chronic alcohol (ethanol) consumption during pregnancy results in maternal/fetal hypocalcemia, which may underlie some of ethanol's adverse effects on maternal and fetal bone, and fetal/neonatal health. Ethanol appears to alter the relationship between parathyroid hormone (PTH) and blood calcium (Ca) level, and PTH does not increase in response to ethanol-induced hypocalcemia. However, it is not known whether ethanol actually prevents PTH from responding, or whether the ability to regulate blood Ca is intact, but ethanol lowers the level of Ca maintained. The objective of this study was to determine whether chronic ethanol consumption impairs the ability of the pregnant female to increase PTH in response to acute hypocalcemia.

METHODS

Rats were fed isocaloric diets with ethanol (36% ethanol-derived calories, E group) or without ethanol [pair-fed (PF) and control (C) groups], before and throughout 21 days of gestation. On day 21 gestation, rats received an intraperitoneal injection of ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) (300 or 500 mumol/kg body weight) or saline (saline group), or no injection (baseline group). Blood was collected from the baseline group, and at 30 or 60 minutes postinjection (saline and EGTA groups), and analyzed for ionized Ca (iCa), pH, and PTH.

RESULTS

Consistent with previous studies, ethanol consumption decreased blood iCa levels at baseline, but PTH levels did not differ among groups. Administration of EGTA significantly decreased blood iCa levels by 30 minutes, but ethanol did not prevent PTH from increasing in response to the hypocalcemia. In all diet groups, PTH levels were significantly increased by 30 minutes. Ethanol did, however, appear to decrease the maximum PTH level achievable in blood.

CONCLUSIONS

These data suggest that chronic ethanol consumption does not impair the ability of the pregnant rat to raise serum PTH levels in response to acute hypocalcemia, but ethanol's effect on maximal PTH secretion could impair the ability of the pregnant female to sustain high PTH levels in response to chronic hypocalcemia.

Transient neonatal hyperparathyroidism: a presenting feature of mucolipidosis type II

The phenotype of mucolipidosis type II (ML II), a disorder of lysosomal enzyme transport, includes mucopolysaccharidosis type I (Hurler syndrome)-like features and dysostosis multiplex, usually apparent after 6 months of age. We describe here the natural history of neonatal hyperparathyroidism, a recently described presentation of ML II. A female neonate presented with multiple fractures and radiological features of osteopenia and 'rickets-like' changes. Longitudinal evaluation, while the patient was treated with vitamin D 800-3,000 IU/day orally, indicated secondary hyperparathyroidism which resolved, biochemically and radiologically, by age 4 months. Neonatal hyperparathyroidism in ML II is severe, transient, and probably secondary to impaired placental calcium transport, simulating a condition observed in the offspring of chronically hypocalcemic mothers.

[Contribution of genetic testing after diagnosis of hypocalcemia]

Serum calcium is a fine-tuned biological value. In recent years, fundamental research and study of molecular anomalies causing certain hereditary diseases of phosphocalcium metabolism have greatly contributed to our knowledge of the factors involved in this regulation, from the embryogenesis of the parathyroid glands to the assay value of serum calcium. Targeted research on these genetic anomalies would be useful not only for the clinician, but also for the patient, contributing to the etiological search, patient follow-up, and possibly to antenatal diagnosis. The main genetic anomalies identified to date are: CaSR, GNAS, AIRE, VDR, mitochondrial DNA, 22q11 deletion.

Mucolipidosis II presenting as severe neonatal hyperparathyroidism

Mucolipidosis II (ML II or I-cell disease ) (OMIM 252500) is an autosomal recessive lysosomal enzyme targeting disorder that usually presents between 6 and 12 months of age with a clinical phenotype resembling Hurler syndrome and a radiological picture of dysostosis multiplex. When ML II is severe enough to be detected in the newborn period, the radiological changes have been described as similar to hyperparathyroidism or rickets. The biological basis of these findings has not been explored and few biochemical measurements have been recorded. We describe three unrelated infants with ML II who had radiological features of intrauterine hyperparathyroidism and biochemical findings consistent with severe secondary neonatal hyperparathyroidism (marked elevation of serum parathyroid hormone and alkaline phosphatase levels). The vitamin D metabolites were not substantially different from normal and repeatedly normal calcium concentrations excluded vitamin D deficiency rickets and neonatal severe hyperparathyroidism secondary to calcium-sensing receptor gene mutations (OMIM 239200). The pathogenesis of severe hyperparathyroidism in the fetus and newborn with ML II is unexplained. We hypothesize that the enzyme targeting defect of ML II interferes with transplacental calcium transport leading to a calcium starved fetus and activation of the parathyroid response to maintain extracellular calcium concentrations within the normal range.

CONCLUSION

Newborns with mucolipidosis II can present with radiological and biochemical signs of hyperparathyroidism. Awareness of this phenomenon may help in avoiding diagnostic pitfalls and establishing a proper diagnosis and therapy.

Prenatal ethanol exposure has differential effects on fetal growth and skeletal ossification

There is increasing evidence suggesting that the intrauterine environment may influence long-term bone health and the risk of developing osteoporosis in later life. Alcohol (ethanol) is one factor whose presence in the prenatal environment has long-term consequences for the offspring, including permanent growth retardation. Moreover, prenatal ethanol exposure retards both fetal and postnatal bone development. It is unknown if ethanol's effects on skeletal development result from generalized growth retardation or effects specific to skeletal development. Furthermore, the level of ethanol exposure required to produce skeletal effects is unknown. The objectives of this study were to determine (1) if ethanol exerts specific effects on fetal skeletal development that are independent from its effects on general growth, and (2) the level of prenatal ethanol exposure required to affect fetal growth and skeletal ossification. Rats were fed isocaloric diets with ethanol (15%, 25%, or 36% ethanol-derived calories (EDC), approximating low, moderate, and high exposure levels), or without ethanol (pair-fed, PF, or control, C groups), prior to and throughout 21 days of gestation. The degree of E-induced delay in development was determined by comparison of E fetuses on d21 gestation to C fetuses on d17-d21 gestation. Prenatal ethanol exposure at 36% EDC decreased fetal body weight, length, and skeletal ossification compared with PF and C fetuses on d21 gestation. Importantly, effects on ossification, but not body weight or length, were also seen at the more moderate dose of 25% EDC, and the number of bones affected and the severity of effects on ossification tended to increase with dose of ethanol. Comparison of E fetuses on d21 gestation with C fetuses from d17 to 21 gestation indicated that the ethanol-induced delay in development differed for weight and skeletal ossification, and was not uniform among skeletal sites. Taken together, these data suggest that prenatal ethanol exposure has effects on fetal skeletal development that are independent of those on overall fetal growth, and that these effects occur even at moderate levels of maternal drinking. Effects of prenatal ethanol exposure on fetal skeletal development could potentially increase the offspring's risk of osteoporosis later in life.

Thyroid disease and other endocrine disorders in pregnancy

Endocrine disorders, in particular, thyroid disorders, are common in pregnancy. The endocrine adaptation to pregnancy, need for adequate iodine supplementation, and thyroxine replacement are presented. In addition, autoimmune diseases of the thyroid and pituitary that may occur subsequent to the immune changes of pregnancy and the postpartum period are discussed. A brief account of the presentation of other endocrine disorders (ie, pituitary,parathyroid, calcium, adrenal and gonadal disorders) also is given, along with their evaluation and management.

Effect of Duration of Maternal Alcohol Consumption on Calcium Metabolism and Bone in the Fetal Rat

BACKGROUND

Prenatal ethanol exposure can retard fetal growth and delay skeletal development. Ethanol also impairs maternal calcium (Ca) homeostasis and this impairment could mediate some of ethanol's effects on the fetal skeleton. Our previous studies suggest that the duration of maternal ethanol consumption may be an important factor for determining the severity of ethanol's effects on Ca homeostasis and fetal skeletal development. The purpose of this study was, therefore, to determine the effect of the duration of maternal ethanol consumption on fetal growth and skeletal development and to investigate the possibility that ethanol's effects may be related to perturbations in fetal/maternal Ca homeostasis.

METHODS

Rats were fed ethanol (36% ethanol-derived calories) in liquid diets for 3 weeks (days 1-21 of gestation) or 6 weeks (for 3 weeks before and throughout gestation). Fetuses were collected on day 21 of gestation, and body weight and length were measured. Fetuses were stained to determine the degree of skeletal ossification, and fetal blood was analyzed for ethanol, Ca (total and ionic Ca), albumin, parathyroid hormone (PTH), and osteocalcin.

RESULTS

Maternal ethanol consumption decreased fetal growth and delayed fetal skeletal development. Although there was a trend for fetal body length and serum osteocalcin levels to be more severely affected with an increased duration of maternal ethanol consumption, duration had no effect on fetal body weight or skeletal ossification. Fetal Ca homeostasis was also affected by ethanol exposure, with fetal hypocalcemia apparent after 6 weeks of maternal ethanol intake. A significant inverse relationship was found between fetal blood Ca levels and blood alcohol concentration (BAC), suggesting that the severity of the fetal hypocalcemia may have been related to differences in fetal BAC, rather than duration of maternal ethanol intake. Fetal serum PTH levels did not differ significantly among treatment groups indicating that the fetal hypocalcemia was not caused by a decrease in PTH levels.

CONCLUSIONS

Prenatal ethanol exposure impaired Ca homeostasis and skeletal development in the fetal rat. The severity of ethanol's effects was only marginally dependent on the duration of maternal ethanol consumption per se and seemed to be more related to the relative exposure of the fetus to ethanol (fetal BAC). The relationship between the ethanol-induced fetal hypocalcemia and skeletal effects remains to be determined.

Perinatal calcium metabolism: physiology and pathophysiology

Disturbances in mineral homeostasis are common in the neonatal period, especially in premature infants and infants who are hospitalised in an intensive care unit. In many cases these disturbances are thought to be exaggerated responses to the normal physiological transition from the intrauterine environment to neonatal independence. By contrast, some disturbances in calcium homeostasis are the result of genetic defects, which in many instances can now be identified at the molecular level. In other cases hypocalcaemia or hypercalcaemia may result from pathological intrauterine conditions, birth trauma or stress, or fetal immaturity. Diagnosis and management of hypocalcaemia and hypercalcaemia in the neonate and infant requires specific knowledge of perinatal mineral physiology and the unique clinical and biochemical features of newborn mineral metabolism. In this chapter we will provide a brief overview of calcium metabolism with an emphasis on the neonatal transition, followed by discussion of the common causes of hypercalcaemia and hypocalcaemia.

Severe congenital rickets secondary to maternal hypovitaminosis D: a case report

We report a full-term baby boy who presented soon after birth with severe congenital rickets. Maternal and neonatal vitamin D levels were very low and the infant responded well to oral vitamin D. Transient secondary hyperparathyroidism normalised on treatment. The mother's vitamin D deficiency was attributed to the region's cultural dress code which prevents exposure to sunlight. There has not been a previous report of severe congenital rickets from this region.

Parathyroid disorders of pregnancy

Diseases of the parathyroid gland are uncommon in women of childbearing age. However, total serum calcium is lower in normal pregnancy, but ionized serum calcium remains within normal limits. Serum parathyroid levels are slightly decreased in the second half of pregnancy. Primary hyperparathyroidism, if unrecognized, may increase maternal and fetal morbidity, which is related to the level of serum calcium. The most common cause is a single parathyroid adenoma, accounting for about 80% of cases. Maternal complications include acute pancreatitis, hypercalcemia crisis, and toxemia. An increased incidence of prematurity and neonatal hypocalcemia has been reported when maternal hypercalcemia is significantly elevated. Other causes of hypercalcemia are rare in pregnancy. Hypoparathyroidism is seldom seen in pregnancy; the most common cause is after surgical throidectomy. The doses of vitamin D and calcium do not change during pregnancy; however, hypercalcemia may develop in the postpartum period. Serum calcium should be determined at every trimester of pregnancy and at regular intervals after delivery, and in a significant number of patients, the dose of vitamin D should be reduced. Osteoporosis has been recognized most frequently in the last few years. It appears that those patients with a family history of osteoporosis and those on heparin therapy have a tendency to develop symptoms of the disease in pregnancy. Finally, lactation is not contraindicated in women with osteoporosis; although there is a slight decrease in bone density in the few months after delivery, this is a transient event and bone densitometry returns to prepregnancy levels in most women. Recent studies indicate that there is no need for calcium therapy during lactation with few exceptions, such as lactating adolescents, mothers nursing more than one child, and mothers with closely-spaced pregnancies.

Clinical biochemistry of pregnancy

Major adaptations in maternal physiology and metabolism are required for successful pregnancy outcome. Hormonal changes initiated even before conception significantly alter maternal biochemistry early in pregnancy. Steroid hormones, peptide hormones, and prostaglandins interact to expand blood and plasma volume and modulate the maternal capacity to supply energy and nutrients to the fetoplacental unit. As gestation progresses, reference ranges for the concentration of many biochemical parameters change significantly from those found in the nonpregnant state. Gestation-specific reference ranges are essential for correct interpretation of tests used in screening, diagnosis, and monitoring during pregnancy. The use of clinical laboratory tests in the management of high-risk pregnancy are discussed from the perspective of testing before conception and during pregnancy.

Vitamin D deficiency and fetal growth

Vitamin D deficiency in pregnancy has been associated with decreased fetal growth, but previous studies have found no direct relation between the weight of the new-born child and the maternal serum level of 25-hydroxyvitamin D3 (calcidiol). The aim of this study was to evaluate the relation between maternal serum calcium and parathyroid hormone with reduced fetal growth in vitamin D deficient pregnant women. Thirty Pakistani women were included in the study at delivery. Only mothers without known chronic diseases who delivered vaginally after an uncomplicated pregnancy were included. Anthropometric data were recorded, and blood samples were drawn from the mothers 1-4 h after delivery. Nearly all (29/30) the Pakistani women had low (< 30 nmol/l) serum levels of 25-hydroxyvitamin D3. Thirteen of the mothers had high serum parathyroid hormone (PTH) levels (> 5.5 pmol/l). The median (range) level of ionised calcium in serum was 1.23 (1.15-1.28) nmol/l. A positive correlation was found between the level of ionised calcium in maternal serum and the crown-heel length of the infant (Spearman's rho = 0.65, P = 0.002, n = 20). The maternal serum PTH was related inversely to the crown-heel length (Spearman's rho = -0.47, P = 0.01, n = 30). No confounding effect of gestational age, sex of the infant, maternal height and body mass index (BMI) was found. The study indicates that vitamin D deficiency affects fetal growth through an effect on maternal calcium homeostasis.