Thyroid disease and pregnancy

Genetic Causality of Hypothyroidism and Adverse Pregnancy Outcomes: A Combined Mendelian Randomisation Study and Bioinformatics Analysis

Background

Observational studies have shown that hypothyroidism is strongly associated with adverse pregnancy outcomes, and that thyroxine during pregnancy comes mainly from the mother; therefore, thyroid defects in women may lead to problems such as miscarriage due to hormonal instability in early pregnancy, and foetal neurological deficits in mid- to late gestation, but whether there is a genetic causality between the two is still a matter of some controversy.

Objective

Goal to investigate the possible causal association between hypothyroidism and unfavorable pregnancy outcomes through the use of bioinformatics and Mendelian randomization (MR).

Methods

We used Mendelian randomization (MR) analyses using single nucleotide polymorphism (SNP) sites as instrumental variables to infer causal associations between exposures and outcomes. The inverse variance weighting method was primarily used in the analysis. Heterogeneity and horizontal multiplicity tests were also conducted to evaluate the results' robustness and the degree of causality. Lastly, preliminary bioinformatics analyses were conducted to investigate the underlying biological mechanisms.

Results

The resultant variance inverse weighting method found that hypothyroidism increased the risk of developing gestational hypertension (OR=1.054, 95% CI: 1.002-1.110 P=0.042) and poor foetal growth (OR=1.081, 95% CI:1.005-1.162 P=0.035). Heterogeneity tests, multiplicity tests and leave-one-out sensitivity analyses did not reveal any heterogeneity or multiplicity effects in the estimated effects of these three exposure factors on the risk of ovarian dysfunction.

Conclusion

Our research establishes genetically the causal relationship between pregnancy-related hypertension, hypothyroidism, and poor fetal growth-a relationship that could be linked to endosomal and cellular transport.

Neonatal thyrotoxicosis with maternal hypothyroidism

Neonatal Graves' is uncommon, but a potentially fatal condition caused by transplacental transfer of thyroid stimulating immunoglobulin (TSI). It is seen in 1%-5% of infants born to a mother with Graves' disease. Here, we report a unique case of transient neonatal thyrotoxicosis with positive TSI in a premature neonate born to the mother with primary hypothyroidism. A short course of antithyroid drug treatment leads to significant clinical and biochemical improvement followed by complete recovery.

The role of hormones and neurons in cardiomyocyte maturation

The heart undergoes profound morphological and functional changes as it continues to mature postnatally. However, this phase of cardiac development remains understudied. More recently, cardiac maturation research has attracted a lot of interest due to the need for more mature stem cell-derived cardiomyocytes for disease modeling, drug screening and heart regeneration. Additionally, neonatal heart injury models have been utilized to study heart regeneration, and factors regulating postnatal heart development have been associated with adult cardiac disease. Critical components of cardiac maturation are systemic and local biochemical cues. Specifically, cardiac innervation and the concentration of various metabolic hormones appear to increase perinatally and they have striking effects on cardiomyocytes. Here, we first report some of the key parameters of mature cardiomyocytes and then discuss the specific effects of neurons and hormonal cues on cardiomyocyte maturation. We focus primarily on the structural, electrophysiologic, metabolic, hypertrophic and hyperplastic effects of each factor. This review highlights the significance of underappreciated regulators of cardiac maturation and underscores the need for further research in this exciting field.

Thyroid hormone signaling and consequences for cardiac development

The fetal heart undergoes its own growth and maturation stages all while supplying blood and nutrients to the growing fetus and its organs. Immature contractile cardiomyocytes proliferate to rapidly increase and establish cardiomyocyte endowment in the perinatal period. Maturational changes in cellular maturation, size and biochemical capabilities occur, and require, a changing hormonal environment as the fetus prepares itself for the transition to extrauterine life. Thyroid hormone has long been known to be important for neuronal development, but also for fetal size and survival. Fetal circulating 3,5,3'-triiodothyronine (T3) levels surge near term in mammals and are responsible for maturation of several organ systems, including the heart. Growth factors like insulin-like growth factor-1 stimulate proliferation of fetal cardiomyocytes, while thyroid hormone has been shown to inhibit proliferation and drive maturation of the cells. Several cell signaling pathways appear to be involved in this complicated and coordinated process. The aim of this review was to discuss the foundational studies of thyroid hormone physiology and the mechanisms responsible for its actions as we speculate on potential fetal programming effects for cardiovascular health.

Intra-amniotic thyroxine to treat fetal goiter

A 35-year-old pregnant woman visited our department and had been treated with 100 µg of daily oral levothyroxine for hypothyroidism. An ultrasonography screening was performed at 25 weeks gestation and revealed a fetal goiter and an increased amniotic fluid volume. Fetal hypothyroidism was confirmed by cordocentesis and amniotic hormone levels at 26 weeks gestation. We treated the mother with 200 µg of daily oral levothyroxine to optimize the transplacental transfer. A total of four intra-amniotic injections of levothyroxine were administered, resulting in progressive reduction in the fetal thyroid volume of goiter as measured by 3D ultrasonography and increased amniotic fluid volume. Following birth, neonatal serum thyroid stimulating hormone level was within the normal range, but free T4 was reduced. Based on this case, we suggest that monitoring amniotic fluid thyroid hormone concentration and intra-amniotic levothyroxine injection can be used to reduce the thyroid volume of goiters and to prevent polyhydramnios.

Hypothyroidism after cancer and the ability to meet reproductive goals among a cohort of young adult female cancer survivors

OBJECTIVE

To determine whether developing hypothyroidism after cancer treatment is associated with a decreased probability of women being able to meet their reproductive goals.

DESIGN

A population-based cohort study.

SETTING

Not applicable.

PATIENT(S)

A total of 1,282 cancer survivors, of whom 904 met the inclusion criteria for the analysis.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Three outcomes that may indicate reduced fertility, which include failure to achieve desired family size, childlessness, and not achieving pregnancy after at least 6 months of regular unprotected intercourse.

RESULT(S)

We used data from the Furthering Understanding of Cancer Health and Survivorship in Adult (FUCHSIA) Women's Study to examine the association between being diagnosed with hypothyroidism after cancer and meeting reproductive goals. After adjusting for age and other potential confounders, women reporting hypothyroidism after cancer treatment were twice as likely to fail to achieve their desired family size (adjusted odds ratio [aOR] 1.91; 95% confidence interval [CI], 1.09, 3.33) and be childless (aOR 2.13; 95% CI, 1.25, 3.65). They were also more likely to report having unprotected intercourse for at least 6 months without conceiving (aOR 1.37; 95% CI, 0.66, 2.83).

CONCLUSION(S)

Although cancer treatments themselves are gonadotoxic, it is important to consider other medical conditions such as hypothyroidism that occur after cancer treatment when counseling patients on the risks for impaired fertility or a shortened reproductive window.

Neonatal thyrotoxicosis caused by maternal autoimmune hyperthyroidism

Neonatal immune hyperthyroidism is a rare but potentially fatal condition. It occurs in 1-5% of infants born to women with Graves' disease (GD). In most of the cases it is due to maternal antibodies transferred from the mother into the fetal compartment, stimulating the fetal thyroid by binding thyrotropin (thyroid-stimulating hormone, TSH) receptor. We present a case of neonatal thyrotoxicosis due to maternal GD detected at 25 days of age and discuss the potential pitfalls in the diagnosis.

Protocol of the PSYCHOTSH study: association between neonatal thyroid stimulating hormone concentration and intellectual, psychomotor and psychosocial development at 4-5 year of age: a retrospective cohort study

Background

Several European countries, including Belgium, still suffer from mild iodine deficiency. Thyroid stimulating hormone (TSH) concentration in whole blood measured at birth has been proposed as an indicator of maternal iodine status during the last trimester of pregnancy. It has been shown that mild iodine deficiency during pregnancy may affect the neurodevelopment of the offspring. In several studies, elevated TSH levels at birth were associated with suboptimal cognitive and psychomotor outcomes among young children. This paper describes the protocol of the PSYCHOTSH study aiming to assess the association between neonatal TSH levels and intellectual, psychomotor and psychosocial development of 4–5 year old children. The results could lead to a reassessment of the recommended cut-off levels of 5 > mU/L used for monitoring iodine status of the population.

Methods

In total, 380 Belgian 4–5 year old preschool children from Brussels and Wallonia with a neonatal blood spot TSH concentration between 0 and 15 mU/L are included in the study. For each sex and TSH-interval (0–1, 1–2, 2–3, 3–4, 4–5, 5–6, 6–7, 7–8, 8–9 and 9–15 mU/L), 19 newborns were randomly selected from all newborns screened by the neonatal screening centre in Brussels in 2008–2009. Infants with congenital hypothyroidism, low birth weight and prematurity were excluded from the study. Neonatal TSH concentration was measured by the Autodelphia method in dried blood spots, collected by heel stick on filter paper 3 to 5 days after birth. Cognitive abilities and psychomotor development are assessed using the Wechsler Preschool and Primary Scale of Intelligence - third edition - and the Charlop-Atwell Scale of Motor coordination. Psychosocial development is measured using the Child Behaviour Check List for age 1½ to 5 years old. In addition, several socioeconomic, parental and child confounding factors are assessed.

Conclusions

This study aims to clarify the effect of mild iodine deficiency during pregnancy on the neurodevelopment of the offspring. Therefore, the results may have important implications for future public health recommendations, policies and practices in food supplementation. In addition, the results may have implications for the use of neonatal TSH screening results for monitoring the population iodine status and may lead to the definition of new TSH cut-offs for determination of the severity of iodine status and for practical use in data reporting by neonatal screening centres.

Severe congenital non-autoimmune hyperthyroidism associated to a mutation in the extracellular domain of thyrotropin receptor gene

Activating mutations in the TSH Receptor (TSHR) gene have been identified as the molecular basis for congenital non-autoimmune hyperthyroidism. We describe the clinical findings and molecular characterization in a girl who presented severe non-autoimmune hyperthyroidism since birth, born to a mother with autoimmune thyroid disease. She was treated with methylmercaptoimidazol and β-blockers, but remained hyperthyroid and required total thyroidectomy. To characterize the presence of an activating mutation, the whole coding sequence and intron-exon boundaries of TSHR gene were analyzed. The patient was heterozygous for p.Ser281Asn mutation and p.Asp727Glu polymorphism. This recurrent mutation, p.Ser281Asn, characterized in vitro by increased basal production of cAMP, is the unique germline activating gene variant described so far in the extracellular domain of TSH receptor. Interestingly, the patient's mother presented hyperthyroidism but without any TSHR gene activating mutation. Although congenital non-autoimmune hyperthyroidism is a rare condition, it should be investigated when severe disease persists, even in a newborn from an autoimmune hyperthyroid mother, in order to differentiate it from the more common congenital autoimmune disease.

Mild iodine deficiency in pregnancy in Europe and its consequences for cognitive and psychomotor development of children: a review

Despite the introduction of salt iodization programmes as national measures to control iodine deficiency, several European countries are still suffering from mild iodine deficiency (MID). In iodine sufficient or mildly iodine deficient areas, iodine deficiency during pregnancy frequently appears in case the maternal thyroid gland cannot meet the demand for increasing production of thyroid hormones (TH) and its effect may be damaging for the neurodevelopment of the foetus. MID during pregnancy may lead to hypothyroxinaemia in the mother and/or elevated thyroid-stimulating hormone (TSH) levels in the foetus, and these conditions have been found to be related to mild and subclinical cognitive and psychomotor deficits in neonates, infants and children. The consequences depend upon the timing and severity of the hypothyroxinaemia. However, it needs to be noted that it is difficult to establish a direct link between maternal iodine deficiency and maternal hypothyroxinaemia, as well as between maternal iodine deficiency and elevated neonatal TSH levels at birth. Finally, some studies suggest that iodine supplementation from the first trimester until the end of pregnancy may decrease the risk of cognitive and psychomotor developmental delay in the offspring.

Side effects of anti-thyroid drugs and their impact on the choice of treatment for thyrotoxicosis in pregnancy

INTRODUCTION

Hyperthyroidism in pregnancy is a serious condition and its management is complex. Whilst carbimazole/methimazole (CBZ/MMI) and propylthiouracil (PTU) have similar efficacies in controlling hyperthyroidism, their risk of side effects such as major congenital abnormalities and hepatotoxicity are different.

METHODS

Various combinations of the terms 'anti-thyroid drugs', 'thionamide', 'carbimazole', 'methimazole', 'propylthiouracil', 'pregnancy', 'side effects', 'agranulocytosis', 'birth defects', 'congenital malformations', 'embryopathy', 'aplasia cutis', 'hepatotoxicity', 'hepatic failure', 'maternal' and 'fetus' were used to search MEDLINE and the Cochrane library. The references of retrieved papers were also reviewed.

RESULTS

There is increasing evidence for a CBZ/MMI embryopathy, whilst data remain lacking for major congenital abnormalities with PTU. In contrast, PTU is associated with increased risk of severe liver injury. Management strategies to reduce these risks by using PTU in the first trimester and CBZ/MMI in the later trimesters remain untested.

CONCLUSION

More evidence is still needed in defining the relative risks between CBZ/MMI and PTU of major congenital abnormalities and severe liver injury in pregnancy. Studies are also needed to establish the suitability of recent management suggestions in switching from PTU to CBZ/MMI after the first trimester. Major adverse outcomes secondary to CBZ/MMI and PTU are rare, and inadequately treated hyperthyroidism poses a far greater risk.

Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline

OBJECTIVE

The aim was to update the guidelines for the management of thyroid dysfunction during pregnancy and postpartum published previously in 2007. A summary of changes between the 2007 and 2012 version is identified in the Supplemental Data (published on The Endocrine Society's Journals Online web site at http://jcem.endojournals.org).

EVIDENCE

This evidence-based guideline was developed according to the U.S. Preventive Service Task Force, grading items level A, B, C, D, or I, on the basis of the strength of evidence and magnitude of net benefit (benefits minus harms) as well as the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe both the strength of recommendations and the quality of evidence.

CONSENSUS PROCESS

The guideline was developed through a series of e-mails, conference calls, and one face-to-face meeting. An initial draft was prepared by the Task Force, with the help of a medical writer, and reviewed and commented on by members of The Endocrine Society, Asia and Oceania Thyroid Association, and the Latin American Thyroid Society. A second draft was reviewed and approved by The Endocrine Society Council. At each stage of review, the Task Force received written comments and incorporated substantive changes.

CONCLUSIONS

Practice guidelines are presented for diagnosis and treatment of patients with thyroid-related medical issues just before and during pregnancy and in the postpartum interval. These include evidence-based approaches to assessing the cause of the condition, treating it, and managing hypothyroidism, hyperthyroidism, gestational hyperthyroidism, thyroid autoimmunity, thyroid tumors, iodine nutrition, postpartum thyroiditis, and screening for thyroid disease. Indications and side effects of therapeutic agents used in treatment are also presented.

A Case of Propylthiouracil-Induced Hepatitis during Pregnancy

A 32-year-old with no pre-existing liver disease was diagnosed with Graves' disease at week 4 of pregnancy. Thyroid-stimulating hormone was undetectable with elevated free thyroxine levels and positive thyroid receptor antibodies. She was started on a reducing regime of propylthiouracil (PTU). At week 20 in pregnancy, she became jaundiced. Initial bloods revealed: bilirubin 91 μmol/l, alanine aminotransferase 1,796 IU/l, alkaline phosphatase 200 IU/l, international normalized ratio 1.2, and albumin 33 g/l. A presumptive diagnosis of PTU-induced hepatitis was made. PTU was immediately discontinued and best supportive care instigated. Serum markers for autoimmune and viral hepatitis were negative, abdomen ultrasound, ferritin and caeruloplasmin were normal. Although her alanine aminotransferase began to fall, her bilirubin continued to rise, peaking at 378. Two weeks after PTU cessation she became thyrotoxic and was started on a reducing regime of carbimazole. Her thyroid function stabilized and liver function tests continued to improve with carbimazole stopped at week 32. Growth scans remained normal with delivery of a healthy baby at 38 weeks. This report highlights that good outcomes can be achieved in PTU-induced hepatitis in pregnancy. Patients on PTU should be warned of the potential risk of hepatic failure and advised to seek medical advice immediately if they develop jaundice.

Thyroid hormone drives fetal cardiomyocyte maturation

Tri-iodo-l-thyronine (T(3)) suppresses the proliferation of near-term serum-stimulated fetal ovine cardiomyocytes in vitro. Thus, we hypothesized that T(3) is a major stimulant of cardiomyocyte maturation in vivo. We studied 3 groups of sheep fetuses on gestational days 125-130 (term ∼145 d): a T(3)-infusion group, to mimic fetal term levels (plasma T(3) levels increased from ∼0.1 to ∼1.0 ng/ml; t(1/2)∼24 h); a thyroidectomized group, to produce low thyroid hormone levels; and a vehicle-infusion group, to serve as intact controls. At 130 d of gestation, sections of left ventricular freewall were harvested, and the remaining myocardium was enzymatically dissociated. Proteins involved in cell cycle regulation (p21, cyclin D1), proliferation (ERK), and hypertrophy (mTOR) were measured in left ventricular tissue. Evidence that elevated T(3) augmented the maturation rate of cardiomyocytes included 14% increased width, 31% increase in binucleation, 39% reduction in proliferation, 150% reduction in cyclin D1 protein, and 500% increase in p21 protein. Increased expression of phospho-mTOR, ANP, and SERCA2a also suggests that T(3) promotes maturation and hypertrophy of fetal cardiomyocytes. Thyroidectomized fetuses had reduced cell cycle activity and binucleation. These findings support the hypothesis that T(3) is a prime driver of prenatal cardiomyocyte maturation.

Thyroid function and human reproductive health

Via its interaction in several pathways, normal thyroid function is important to maintain normal reproduction. In both genders, changes in SHBG and sex steroids are a consistent feature associated with hyper- and hypothyroidism and were already reported many years ago. Male reproduction is adversely affected by both thyrotoxicosis and hypothyroidism. Erectile abnormalities have been reported. Thyrotoxicosis induces abnormalities in sperm motility, whereas hypothyroidism is associated with abnormalities in sperm morphology; the latter normalize when euthyroidism is reached. In females, thyrotoxicosis and hypothyroidism can cause menstrual disturbances. Thyrotoxicosis is associated mainly with hypomenorrhea and polymenorrhea, whereas hypothyroidism is associated mainly with oligomenorrhea. Thyroid dysfunction has also been linked to reduced fertility. Controlled ovarian hyperstimulation leads to important increases in estradiol, which in turn may have an adverse effect on thyroid hormones and TSH. When autoimmune thyroid disease is present, the impact of controlled ovarian hyperstimulation may become more severe, depending on preexisting thyroid abnormalities. Autoimmune thyroid disease is present in 5-20% of unselected pregnant women. Isolated hypothyroxinemia has been described in approximately 2% of pregnancies, without serum TSH elevation and in the absence of thyroid autoantibodies. Overt hypothyroidism has been associated with increased rates of spontaneous abortion, premature delivery and/or low birth weight, fetal distress in labor, and perhaps gestation-induced hypertension and placental abruption. The links between such obstetrical complications and subclinical hypothyroidism are less evident. Thyrotoxicosis during pregnancy is due to Graves' disease and gestational transient thyrotoxicosis. All antithyroid drugs cross the placenta and may potentially affect fetal thyroid function.

Short term hypothyroidism affects ovarian function in the cycling rat

BACKGROUND

Rats made hypothyroid with propilthyouracil start showing abnormal cycling on the second cycle after the start of the treatment, with a high proportion of spontaneous pseudopregnancies and reduced fertility.

METHODS

To investigate some of the mechanisms involved in these reproductive abnormalities, hypothyroidism was induced in virgin rats by propilthyouracil (0.1 g/L in the drinking water) and we determined circulating hormones by radioimmunoassay and whole ovary expression of ovarian hormone receptors, growth factors and steroidogenic enzymes using semi-quantitative RT-PCR.The study was performed on days 6 to 9 of treatment, corresponding to diestrus I (at 20.00-22.00 h), diestrus II (at 20.00-22.00 h), proestrus and estrus (both at 8.00-10.00 h and 20.00-22.00 h) of the second estrous cycle after beginning propilthyouracil treatment. Another group of rats was mated on day 8 and the treatment continued through the entire pregnancy to evaluate reproductive performance.

RESULTS

Hypothyroidism increased circulating prolactin and estradiol on estrus 5 to 7-fold and 1.2 to 1.4-fold respectively. Growth hormone and insulin-like growth factor 1 diminished 60 and 20% respectively on proestrus morning. Hypothyroidism doubled the ovarian mRNA contents of estrogen receptor-beta on proestrus and estrus evenings, cyp19A1 aromatase mRNA on estrus evening and of growth hormone receptor on proestrus evening. Hypothyroidism did not influence ovulation rate or the number of corpora lutea at term, but a diminished number of implantation sites and pups per litter were observed (Hypothyroid: 11.7 +/- 0.8 vs.

CONTROL

13.9 +/- 0.7).

CONCLUSIONS

Short term hypothyroidism alters normal hormone profile in the cycling rat increasing the expression of estrogen receptor-beta and cyp19A1 aromatase on estrus, which in turn may stimulate estradiol and prolactin secretion, favouring corpus luteum survival and the subsequent instauration of pseudopregnancy.

Maternal thyroid disease, thyroid medication use, and selected birth defects in the National Birth Defects Prevention Study

BACKGROUND

Although thyroid disorders are present in approximately 3% of pregnant women, little is known about the association between maternal thyroid disease and birth defects.

METHODS

We assessed the association between maternal thyroid disease, thyroid medication use, and 38 types of birth defects among 14,067 cases and 5875 controls in the National Birth Defects Prevention Study, a multisite, population-based, case-control study. Infants in this study were born between October 1997 and December 2004. Information on exposures including maternal diseases and use of medications was collected by telephone interview.

RESULTS

We found statistically significant associations between maternal thyroid disease and left ventricular outflow tract obstruction heart defects (1.5; 95% CI, 1.0-2.3), hydrocephaly (2.9; 95% CI, 1.6-5.2), hypospadias (1.6; 95% CI, 1.0-2.5), and isolated anorectal atresia (2.4; 95% CI, 1.2-4.6). Estimates for the association between periconceptional use of thyroxine and specific types of birth defects were similar to estimates for any thyroid disease. Given that antithyroid medication use was rare, we could not adequately assess risks for their use for most case groups.

CONCLUSIONS

Our results are consistent with the positive associations between maternal thyroid disease or thyroid medication use and both hydrocephaly and hypospadias observed in some previous studies. New associations with left ventricular outflow tract obstruction heart defects and anorectal atresia may be chance findings.

Adverse effects of thyroid dysfunction on pregnancy and pregnancy outcome: Epidemiologic study in Slovenia

OBJECTIVE

To evaluate the consequences of maternal thyroid dysfunction for pregnancy outcome.

METHODS

A retrospective analysis involving all pregnant women who delivered in Slovenia in the 1997-1999 triennium; those having a medical history of thyroid dysfunction and/or taking thyroid medications were allotted to the study group (n = 748) and the remaining ones to the control group (n = 52 253).

RESULTS

Significantly higher incidences of infertility (5.5% vs. 3.7%, p < 0.05), menstrual cycle irregularities (3.2% vs. 1.9%, p < 0.05), hypertensive disorders (7.0% vs. 4.2%, p < 0.05), threatened preterm delivery (9.1% vs. 5.6%, p < 0.001), and delivery before 32 weeks (2.7% vs. 1.5%, p < 0.05) were found in the study than in the control group. There were no significant differences in the incidences of miscarriage, non-gestational diabetes mellitus, proteinuria, hyperemesis, intrahepatic cholestasis of pregnancy, intrauterine growth restriction, placental abruption, preterm delivery, small for gestational age newborns (SGA), and stillbirths.

CONCLUSIONS

This is the first study to evaluate the incidence of thyroid dysfunction for the whole population of pregnant women in Slovenia using a retrospective analysis. Thyroid dysfunction adversely affects pregnancy and pregnancy outcome but to a lesser extent than presented in previous studies. An evaluation of thyroid function in the women who experience menstrual cycle irregularities, infertility, and complications during pregnancy, labor and delivery would be advisable.

Autoimmune Thyroid Disease and Pregnancy: Relevance for the Child

As a group, the autoimmune thyroid diseases, including Graves' disease, Hashimoto's thyroiditis, and primary myxedema, are among the most common endocrine disorders encountered during pregnancy. Therefore, a substantial number of offspring will grow and develop in utero under conditions of maternal autoimmune thyroid disease and may be exposed to abnormal maternal thyroid function, maternal thyroid antibodies, and/or numerous therapeutic agents used to manage maternal thyroid dysfunction. This article reviews the effects that these various aspects of maternal autoimmune thyroid disorders can have on pregnancy outcome, as well as on the physical growth, neuropsychological development, and thyroid status of the developing fetus and neonate.

Adjustment of L-T4 substitutive therapy in pregnant women with subclinical, overt or post-ablative hypothyroidism

OBJECTIVE

Maternal hyperthyrotropinaemia is associated with an increased risk of adverse maternal and neonatal outcomes. Physiological changes during pregnancy require an increased production of thyroid hormones (or an increase in daily substitutive doses of L-T4 in hypothyroid patients) to meet the maternal and foetal needs. The aim of the study was to evaluate variations of substitutive L-T4 doses that are able to maintain serum TSH between 0.5 and 2.5 mU/l in pregnant women with subclinical- (SH), overt- (OH) and post-ablative (PH) hypothyroidism.

DESIGN

This was a retrospective study on hypothyroid pregnant women referred to the out-patient department between January 2004 and December 2006.

PATIENTS AND MEASUREMENTS

A total of 185 pregnant women were studied during gestation; 155 patients (76 SH, 52 OH, 27 PH) were already on L-T4 before conception and 30 (SH) started L-T4 therapy during gestation. Thyroid function and body weight were evaluated every 4-6 weeks.

RESULTS

In the group of patients already treated before conception, 134 (86.5%) increased L-T4 doses during gestation one or more times, eight (6%) reached a definitive therapeutic dosage within the 12th week of pregnancy, 64 (47.8%) within the 20th week and 62 (46.2%) within the 31st week. This initial L-T4 increase at the first evaluation during pregnancy was 22.9 +/- 9.8 microg/day. The final L-T4 doses were significantly different depending on the aetiology, being 101.0 +/- 24.6 microg/day in SH, 136.8 +/- 30.4 microg/day in OH and 159.0 +/- 24.6 microg/day in PH. The per cent increase of L-T4, expressed as Delta% of absolute dose, was +70% in SH, +45% in OH and +49% in PH as compared to baseline dose. In SH patients diagnosed during gestation, the starting L-T4 dose was higher than L-T4 dose before pregnancy of SH patients already treated (75.4 +/- 14.5 and 63.2 +/- 20.1 microg/day, respectively), whereas the final doses were similar. L-T4 dose was increased one or more times in 24 patients (80%), 8 reached the definitive dosage within the second trimester (33.3%) and 16 within the third trimester (66.7%).

CONCLUSIONS

Serum TSH and FT4 measurements are mandatory in pregnant patients and the optimal timing for increasing L-T4 is the first trimester of pregnancy, though many patients require adjustments also during the second and third trimester. The aetiology of hypothyroidism influences the adjustment of L-T4 therapy and SH patients needed a larger increase than OH and PH. Close monitoring during pregnancy appears to be mandatory in hypothyroid women.

Effects of maternal levels of thyroid hormone (TH) on the hypothalamus-pituitary-thyroid set point: studies in TH receptor beta knockout mice

A level of thyroid hormone (TH) in agreement with the tissue requirements is essential for vertebrate embryogenesis and fetal maturation. In this study we evaluate the immediate and long-term effects of incongruent intrauterine TH levels between mother and fetus using the TH receptor (TR) beta(-/-) knockout mouse as a model. We took advantage of the fact that the TRbeta(-/-) females have elevated serum TH but are not thyrotoxic due to resistance to TH. We used crosses between heterozygotes with wild-type phenotype (TRbeta(+/-)) males and TRbeta(-/-) females, with a hyperiodothyroninemic (high T(4) and T(3) levels) intrauterine environment (TH congruent with the TRbeta(-/-) fetus and excessive for the TRbeta(+/-) fetus), and reciprocal crosses between TRbeta(-/-) males and TRbeta(+/-) females, providing a euiodothyroninemic intrauterine environment. We found that TRbeta(-/-) dams had reduced litter sizes and pups with lower birth weight but preserved the mendelian TRbeta(-/-) to TRbeta(+/-) ratio at birth, indicating that the incongruous TH levels did not decrease intrauterine survival of a specific genotype. The results of studies in newborns demonstrate that TRbeta(+/-) pups born to TRbeta(-/-) dams have persistent suppression of serum TSH without a peak. On the other hand, TRbeta(-/-) pups born to TRbeta(+/-) dams have lower serum TSH at birth and a tendency to peak higher, compared with TRbeta(-/-) pups born to TRbeta(-/-) dams. The studies in the adult progeny demonstrate that TRbeta(+/-) mice born to TRbeta(-/-) dams and, thus, exposed to higher intrauterine TH levels, have greater resistance to TH at the level of the pituitary when stimulated with TRH. On the other hand, TRbeta(-/-) mice born to TRbeta(+/-) dams and, thus, deprived of TH in uterine life, were more sensitive to TH when similarly stimulated with TRH. Thus, TH exposure in utero has an effect on the regulatory set point of the hypothalamus-pituitary-thyroid axis, which can be seen early in life and persists into adulthood.

Two cases of subacute thyroiditis presenting in pregnancy

Subacute thyroiditis (SAT) is an extremely rare cause of thyrotoxicosis in pregnant women. Untreated, thyrotoxicosis may result in complications, such as prematurity and congenital malformations in the fetus. We report two cases of first trimester subacute thyroiditis, one mild and one severe. The severe case, as demonstrated by laboratory and ultrasound findings, was successfully treated with prednisolone. In this case, it was thought that the benefits of pharmacological therapy outweighed the risk of potential teratogenesis by the medication. In contrast, the milder case was managed conservatively and resolved without treatment. These cases illustrate how laboratory and ultrasound findings can be used to determine whether treatment should be initiated and, once begun, if medication levels need to be adjusted. In both cases, the pregnancies resulted in healthy full-term infants.

Status of anti-thyroid peroxidase during normal pregnancy and in patients with hyperemesis gravidarum

Autoimmune thyroid diseases (AITD) comprising Hashimoto's thyroiditis, primary myxedema, and Graves' disease are associated with autoantibodies directed against thyroglobulin and thyroid peroxidase (anti-TPO). Anti-TPO occur in 10% of pregnant women, half of whom reportedly develop postpartum thyroid dysfunction. We recently published data on the thyroid function reference ranges in pregnant Chinese but the AITD status of our cohort was unknown. In view of this missing information we have measured anti-TPO in specimens from our cohort stored at -80 degrees C, and compared these to those of patients with hyperemesis gravidarum (HG) and nonpregnant controls. After eliminating 3 outliers from 47 nonpregnant controls, the anti-TPO concentration range was 2.2-14.7 kIU/L (n = 44). In 282 pregnant control subjects, the anti-TPO levels were less than 14.7 kIU/L (upper limit of nonpregnant controls) in 189 (67%); between 14.7-55 kIU/L in 82 (29.1%); and greater than 55 kIU/L in 11 (3.9%). The percentage of women with anti-TPO greater than 14.7 kIU/L during the first, second, and third trimesters were 47% (30/64), 39% (49/126), and 16% (15/92), respectively. Anti-TPO level was significantly higher in pregnant controls compared to nonpregnant controls and patients with HG. With reference to other studies in which anti-TPO levels greater than 60 kIU/L were considered pathologic, we conclude that more than 96% of our pregnant controls were without AITD and the data on thyroid function reference ranges we previously reported remain valid.

[Detection of subclinical hypothyroidism in pregnant women with different gestational ages]

AIM

To detect subclinical hypothyroidism in pregnant women.

SUBJECTS AND METHODS

Seventy-five pregnant women who resided in the town of Itabuna, state of Bahia, were voluntarily studied. Inclusion criteria were age < 40 years, no history of previous thyroid disease, autoimmunopathy or diabetes mellitus, and any gestational age; a clinical evaluation (an interview obeying to a questionnaire); laboratory evaluation (free T4, TSH, anti-TPO antibody, total and HDL cholesterol, triglyceride determinations); thyroid ultrasonography.

RESULTS

Average age was 21.6 +/- 5.1 (14-40 years); gestation age was 24.2 +/- 8.2 (5-39 weeks); an elevated TSH with normal free T4 was found in 3 cases (4.0%). Anti-TPO antibodies were positive in 8.0% on the pregnant women. In 5.4% of them, thyroid ultrasonographic changes were documented.

CONCLUSION

Based on finding of a 4% prevalence of elevated TSH during pregnancy, the authors consider important the inclusion of thyroid function laboratory evaluation in the routine prenatal examination. Further studies appear necessary to establish at what gestational age thyroid function evaluation should be started in pregnant women and how frequently it should be repeated during the course of gestation.

Maternal hypothyroidism in early and late gestation: effects on neonatal and obstetric outcome

BACKGROUND

Maternal hypothyroidism may be associated with a variety of adverse neonatal and obstetric outcomes. Whether these outcomes are affected by maternal thyroid status at initial presentation or in late gestation specifically within a dedicated antenatal endocrine clinic remains unclear. The effects of thyroxine dose requirement during pregnancy and serum concentrations of TSH within such clinic settings are still not known.

OBJECTIVES

We investigated these outcomes in patients with hypothyroidism during early and late gestation. TSH levels and thyroxine dose requirement during early and late gestation were also evaluated.

METHODS

We performed a retrospective study of data from 167 pregnancies managed in the antenatal endocrine clinic. Analysis of outcomes was linked to TSH at first presentation and in the third trimester. Outcome variables included: rate of caesarean section, pre-eclampsia, neonatal unit admission, neonatal weight and gestational age. Controlled TSH was defined as mothers with TSH between 0.1 and 2 with normal free thyroid hormone levels.

RESULTS

The caesarean section (CS) rates were higher in the study cohort (H) compared with the local (C) rate (H = 28.7%, C = 18%). The higher rate in our patient cohort was not due to a higher rate of emergency section nor to a lower threshold for performing elective caesarean section. The infant birthweight (IBW) from mothers with TSH > 5.5 (H1) and mothers with TSH between 0.1 and 5.5 at presentation (H2) was [median (range)] 3.38 (1.73-4.70) vs. 3.45 (1.36-4.76); P = ns. The prevalence of low-birthweight (LBW) infants (< 2.5 g) in groups H1 and H2 was 15% and 4.8%, respectively [odds ratio (OR) = 3.55, 95% confidence interval (95% CI) = 0.96-10.31]. IBW from mothers with TSH > 2 (H3) and mothers with controlled TSH in the third trimester (H4) were similar [3.38 (1.78-4.4) vs. 3.46 (1.36-4.76); P = ns]. The prevalence of LBW in groups H3 and H4 was 9% and 4.9%, respectively (OR = 1.95, 95% CI = 0.52-7.26). The median thyroxine dose (microg) increased significantly during pregnancy (first trimester: 100; second trimester: 125, P < 0.001; and third trimester: 150, P < 0.001) associated with appropriate suppression of TSH levels in the second and third trimesters. Rates of pre-eclampsia or admissions to neonatal units were negligible.

CONCLUSION

Thyroxine dose requirement increases during pregnancy and thus close monitoring of thyroid function with appropriate adjustment of thyroxine dose to maintain a normal serum TSH level is necessary throughout gestation. Within a joint endocrine-obstetric clinic, maternal hypothyroidism at presentation and in the third trimester may increase the risk of low birthweight and the likelihood for caesarean section. The latter observation was not due to a higher rate of emergency caesarean section nor to a lower threshold for performing elective caesarean section. A larger study with adjustments made for the various confounders is required to confirm this observation.

Hyperthyroidism impairs pancreatic beta cell adaptations to late pregnancy and maternal liporegulation in the rat

AIMS/HYPOTHESIS

Hyperthyroidism modifies lipid dynamics (increased oxidation), impairs insulin action and can suppress insulin secretion. We therefore examined the impact of hyperthyroidism on the relationship between glucose-stimulated insulin secretion (GSIS) and insulin action, using late pregnancy as a model of physiological insulin resistance that is associated with compensatory insulin hypersecretion to maintain glucose tolerance. Our aim was to examine whether hyperthyroidism compromises the regulation of insulin secretion and the ability of insulin to modulate circulating lipid concentrations in late pregnancy.

MATERIALS AND METHODS

Hyperthyroidism was induced by tri-iodothyronine (T(3)) administration from day 17 to 19 of pregnancy. GSIS was assessed during an IVGTT and during hyperglycaemic clamps in vivo and in vitro, using step-up and -down islet perifusions.

RESULTS

Hyperthyroidism in pregnancy elevated the glucose threshold for GSIS and impaired GSIS at low and high glucose concentrations in islet perifusions. In the intact animal, insulin secretion (after bolus glucose) was more rapidly curtailed following removal of the glucose stimulus to secretion. In contrast, GSIS was maintained during protracted hyperglycaemia (hyperglycaemic clamps) in the hyperthyroid pregnant state in vivo.

CONCLUSIONS/INTERPRETATION

Hyperthyroidism in vivo during late pregnancy blunts GSIS in subsequently isolated and perifused islets at low and high glucose concentrations. It also adversely affects GSIS under conditions of an acute glucose challenge in vivo. In contrast, GSIS is maintained during sustained hyperglycaemia in vivo, suggesting that in vivo factors can rescue GSIS. The ability of insulin to suppress systemic lipid levels during hyperglycaemic clamps was impaired. We therefore suggest that higher circulating lipids may preserve GSIS under conditions of sustained hyperglycaemia in the hyperthyroid pregnancy.

Study of lens autofluorescence by fluorophotometry in pregnancy

Lens autofluorescence originates from an accumulation of fluorescent substances such as the tryptophan-derived residues and protein aggregations, which are associated with the preclinical progress of cataractogenesis, diabetes and lens aging. Our purpose is to determine if pregnancy alters the typical constituents of the lens autofluorescence. Fifteen healthy pregnant women (22 eyes) who were in their third trimester of pregnancy and 23 age-matched healthy controls (37 eyes, non-pregnant females). Lens autofluorescence, lens transmission and corneal autofluorescence were studied with fluorophotometry. The lens autofluorescence values were 358+/-151 ng ml(-1) in the control group and 201+/-110 ng ml(-1) in the pregnants women. The difference was significant (p=0.0074). Lens transmission values were 0.93+/-0.02 ng ml(-1) in the control group and 0.94+/-0.02 ng ml(-1) in the pregnants women: the difference was not significant. Corneal autofluorescence values were 21.9+/-7.5 ng ml(-1) in the control group and 18.2+/-5.8 ng ml(-1) in the pregnant women. The difference was not significant. Our study showed a significant decrease in lens autofluorescence in pregnant women compared to a normal population. The decrease can be partly attributed to the aqueous component of the lens that increases significantly during the final trimester of pregnancy and that this provokes a dilution of the fluorescent substances.

Degenerate self-reactive human T-cell receptor causes spontaneous autoimmune disease in mice

Thyroid autoimmune disorders comprise more than 30% of all organ-specific autoimmune diseases and are characterized by autoantibodies and infiltrating T cells. The pathologic role of infiltrating T cells is not well defined. To address this issue, we generated transgenic mice expressing a human T-cell receptor derived from the thyroid-infiltrating T cell of a patient with thyroiditis and specific for a cryptic thyroid-peroxidase epitope. Here we show that mouse major histocompatibility complex molecules sustain selection and activation of the transgenic T cells, as coexpression of histocompatibility leukocyte antigen molecules was not needed. Furthermore, the transgenic T cells had an activated phenotype in vivo, and mice spontaneously developed destructive thyroiditis with histological, clinical and hormonal signs comparable with human autoimmune hypothyroidism. These results highlight the pathogenic role of human T cells specific for cryptic self epitopes. This new 'humanized' model will provide a unique tool to investigate how human pathogenic self-reactive T cells initiate autoimmune diseases and to determine how autoimmunity can be modulated in vivo.

Hypothyroidism and chronic autoimmune thyroiditis in the pregnant state: maternal aspects

Hypothyroidism during pregnancy is associated with adverse outcomes that can be ameliorated or prevented by adequate therapy with thyroxine. Currently, there are no guidelines for universal screening for thyroid dysfunction in pregnant women or in women of reproductive age. Therefore, it is important to recognize those groups of women who may be at higher risk for development of hypothyroidism so that serum TSH testing may be performed with appropriate initiation of thyroxine therapy. In addition, the thyroxine therapy of women with established hypothyroidism should be optimized prior to conception and during pregnancy when the thyroxine dosage requirement generally increases early in gestation. The diverse etiologies of maternal hypothyroidism may require different increments in thyroxine dose during pregnancy, and generally the postpartum dosage requirement returns to pre-pregnancy levels.

Thyroid function and intellectual development of children of mothers taking methimazole during pregnancy

There is some debate regarding the safety of methimazole (MMI) therapy during pregnancy. It is not known whether MMI therapy in mothers during pregnancy is safe for their children or if it causes alterations in thyroid function and intellectual development during childhood. Twenty-three children, whose mothers were hyperthyroid during pregnancy and treated with MMI 5-20 mg were studied from age 3-11 yr. Thyroid function and liver function tests, urinary iodine, anti-thyroid antibodies, intelligence quotient (IQ), verbal and functional components of Wechsler test were performed on 23 children of thyrotoxic mothers and 30 controls. In all children T3, T4, RT3U and TSH concentrations were normal. Mean T3, T4 and TSH values were 147 ng/dl, 9.7 microg/dl and 1.2 mU/l, respectively. Height, weight, thyroid function, and thyroid antibodies did not differ from controls. None of the children had T4 below 6 microg/dl or TSH>3.0 mU/l. Liver enzymes and serum albumin were normal in both groups. Mann-Whitney test showed no difference in verbal and performance IQ and their components between children of thyrotoxic mothers and controls. Total IQ of cases and controls was 117 +/- 11 and 113 +/- 14, respectively. No deleterious effect occurred in thyroid function and physical and intellectual development of children whose mothers were treated during pregnancy with doses of MMI up to 20 mg daily.

Thyroid hormone is a critical determinant for the regulation of the cochlear motor protein prestin

The most impressive property of outer hair cells (OHCs) is their ability to change their length at high acoustic frequencies, thus providing the exquisite sensitivity and frequency-resolving capacity of the mammalian hearing organ. Prestin, a protein related to a sulfate/anion transport protein, recently has been identified and proposed as the OHC motor molecule. Homology searches of 1.5 kb of genomic DNA 5' of the coding region of the prestin gene allowed the identification of a thyroid hormone (TH) response element (TRE) in the first intron upstream of the prestin ATG codon. Prestin(TRE) bound TH receptors as a monomer or presumptive heterodimer and mediated a triiodothyronine-dependent transactivation of a heterologous promotor in response to triiodothyronine receptors alpha and beta. Retinoid X receptor-alpha had an additive effect. Expression of prestin mRNA and prestin protein was reduced strongly in the absence of TH. Although prestin protein typically was redistributed to the lateral membrane before the onset of hearing, an immature pattern of prestin protein distribution across the entire OHC membrane was noted in hypothyroid rats. The data suggest TH as a first transcriptional regulator of the motor protein prestin and as a direct or indirect modulator of subcellular prestin distribution.

Maternal medical disease: risk of antepartum fetal death

Although certain maternal medical conditions increase the risk of antepartum fetal death, improvements in medical and obstetric care have decreased the likelihood of stillbirth. This article examines the current stillbirth rates reported in pregnancies complicated by common medical diseases. The reported stillbirth rates are expressed as the number of stillbirths occurring at > or = 20 weeks of gestation per 1,000 births in patients with the condition. Overall, about 10% of all fetal deaths are related to maternal medical illnesses such as hypertension, diabetes, obesity, systemic lupus erythematosus, chronic renal disease, thyroid disorders, and cholestasis of pregnancy. The early recognition of maternal medical diseases provides an opportunity for increased surveillance and interventions that may lead to more favorable pregnancy outcomes.

Thyroid hormone-deficient period prior to the onset of hearing is associated with reduced levels of beta-tectorin protein in the tectorial membrane: implication for hearing loss

The genes for alpha- and beta-tectorin encode the major non-collagenous proteins of the tectorial membrane. Recently, a targeted deletion of the mouse alpha-tectorin gene was found to cause loss of cochlear sensitivity (). Here we describe that mRNA levels for beta-tectorin, but not alpha-tectorin, are significantly reduced in the cochlear epithelium under constant hypothyroid conditions and that levels of beta-tectorin protein in the tectorial membrane are lower. A delay in the onset of thyroid hormone supply prior to onset of hearing, recently described to result in permanent hearing defects and loss of active cochlear mechanics (), can also lead to permanently reduced beta-tectorin protein levels in the tectorial membrane. beta-Tectorin protein levels remain low in the tectorial membrane up to one year after the onset of thyroid hormone supply has been delayed until postnatal day 8 or later and are associated with an abnormally structured tectorial membrane and the loss of active cochlear function. These data indicate that a simple delay in thyroid hormone supply during a critical period of development can lead to low beta-tectorin levels in the tectorial membrane and suggest for the first time that beta-tectorin may be required for development of normal hearing.

Hyperthyroidism affects lipid metabolism in lactating and suckling rats

Two per thousand pregnant women have hyperthyroidism (HT), and although the symptoms are attenuated during pregnancy, they rebound after delivery, affecting infant development. To examine the effects of hyperthyroidism on lactation, we studied lipid metabolism in maternal mammary glands and livers of hyperthyroid rats and their pups. Thyroxine (10 microg/100 g body weight/d) or vehicle-treated rats were made pregnant 2 wk after commencement of treatment and sacrificed on days 7, 14, and 21 of lactation with the litters. Circulating triiodothyronine and tetraiodothyronine concentrations in the HT mothers were increased on all days. Hepatic esterified cholesterol (EC) and free cholesterol (FC) and triglyceride (TG) concentrations were diminished on days 14 and 21. Lipid synthesis, measured by incorporation of [3H]H2O into EC, FC, and TG, fatty acid synthase, and acetyl CoA carboxylase activities increased at day 14, while incorporation into FC and EC decreased at days 7 and 21, respectively. Mammary FC and TG concentrations were diminished at day 14; incorporation of [3H]H2O into TG decreased at days 7 and 21, and incorporation of [3H]H2O into FC increased at day 14. In the HT pups, growth rate was diminished, tetraiodothyronine concentration rose at days 7 and 14 of lactation, and triiodothyronine increased only at day 14. Liver TG concentrations increased at day 7 and fell at day 14, while FC increased at day 14 and only acetyl CoA carboxylase activity fell at day 14. Thus, hyperthyroidism changed maternal liver and mammary lipid metabolism, with decreased lipid concentration in spite of increased liver rate of synthesis and decreases in mammary synthesis. These changes, along with the mild hyperthyroidism of the litters, may have contributed to their reduced growth rate.

Management of a pregnant patient with Graves' disease complicated by thionamide-induced neutropenia in the first trimester

A 31-year-old woman presented with neutropenia due to thionamide drug therapy for Graves' disease. She also reported 8 weeks of amenorrhoea and had a positive pregnancy test. Her drug therapy was discontinued and her neutropenia resolved uneventfully. The hyperthyroidism recurred a week later. After consideration of all treatment options, it was decided to observe until 14 weeks when an elective thyroidectomy was planned. Mother and fetus were monitored closely and both tolerated moderate hyperthyroidism well. At 14 weeks the patient underwent a total thyroidectomy after rendering her euthyroid with a short course of sodium ipodate. Labour was induced at 41 weeks. Delivery was complicated by fetal distress and precipitated a forceps delivery. A 3250 g male infant was born with poor Apgar score and required 2 h of ventilation. At 1 year, the child had reached all developmental milestones at appropriate times. Both mother and fetus may tolerate moderate thyrotoxicosis well in early pregnancy, an alternative that should be considered when thionamide drug therapy is contraindicated.

Effect of maternal hyperthyroidism during late pregnancy on the risk of neonatal low birth weight

OBJECTIVE

Hyperthyroidism in pregnancy occurs with a prevalence of 0.05--0.2% and has been shown to affect neonatal outcomes. Fetal weight increases markedly during the third trimester of pregnancy. This retrospective study was performed to examine the effect of maternal hyperthyroidism during late pregnancy on neonatal birth weight (NBW).

DESIGN

Medical and obstetric records of 293 pregnant women with present and past history of hyperthyroidism were retrospectively reviewed.

PATIENTS

There were 188 records of 181 patients with adequate data for inclusion in the analysis. The patients were divided into two groups according to the maternal thyroid function during the third trimester of pregnancy: hyperthyroidism (HT; 35 cases) and euthyroidism (ET; 153 cases).

MEASUREMENTS

Maternal thyroid function tests were periodically evaluated before and during the third trimester of pregnancy. Neonatal thyroid function tests and birth weight of the newborn infants were also assessed.

RESULTS

There was no significant difference of maternal age between HT and ET groups mean +/- SD (27.6 +/- 5.5 vs. 29.2 +/- 5.4 years). The NBW of the HT group was not significantly different from that of the ET group (2880 +/- 590 vs. 3019 +/- 426 g). However, the prevalence of infants with low birth weight (LBW) defined as NBW of lower than 2500 g in HT group was 22.9% which was significantly higher than the 9.8% in the ET group (P = 0.039, OR = 2.7, 95%CI = 1.1--7.1) and 9.7% of infants born to healthy mothers at Siriraj Hospital (control group) between 1991 and 1995 (P = 0.01, OR = 2.7, 95%CI = 1.3--6.1). The 90% CI for the true difference between the prevalence of LBW infants born to ET and HT mothers was 0.7--25.4. There was no significant difference in the prevalence of LBW infants in ET and control groups. Multiple logistic regression analyses showed that maternal hyperthyroidism during the third trimester of pregnancy was an independent factor associated with increased prevalence of LBW infants (P = 0.037, OR = 4.1, 95%CI = 1.1--15.0).

CONCLUSIONS

Maternal hyperthyroidism during the third trimester of pregnancy independently increases the risk of low birth weight by 4.1-fold. Appropriate management of hyperthyroidism throughout pregnancy is essential in the prevention of this undesirable neonatal outcome.

Effects of amiodarone administration during pregnancy on neonatal thyroid function and subsequent neurodevelopment

Amiodarone, a benzofuranic derivative, iodine-rich drug, has been used in pregnancy for either maternal or fetal tachyarrhythmias. Amiodarone, its main metabolite (desethylamiodarone) and iodine are transferred, albeit incompletely, through the placenta, resulting in a relevant fetal exposure to the drug and iodine overload. Since the fetus acquires the capacity to escape from the acute Wolff-Chaikoff effect only late in gestation, the iodine overload may cause fetal/neonatal hypothyroidism and goiter. Among the reported 64 pregnancies in which amiodarone was given to the mother, 11 cases (17%) of hypothyroidism in the progeny (10 detected at birth, 1 in utero) were reported, 9 non-goitrous (82%) and 2 (18%) associated with goiter. Hypothyroidism was transient in all cases, and only 5 infants were treated short-term with thyroid hormones. Only 2 newborns had transient hyperthyroxinemia, associated with low serum TSH concentrations in one. Neurodevelopment assessment of the hypothyroid infants, when carried out, showed in some instances mild abnormalities, most often reminiscent of the Non-verbal Learning Disability Syndrome; however, these features were also reported in some amiodarone-exposed euthyroid infants, suggesting that there might be a direct neurotoxic effect of amiodarone during fetal life. Breast-feeding was associated with a substantial ingestion of amiodarone by the infant, but in the few cases followed it did not cause changes in the newborn's thyroid function. In conclusion, amiodarone therapy during pregnancy may cause fetal/neonatal hypothyroidism and, less frequently, goiter. Thus, the use of amiodarone in pregnancy should be limited to maternal/fetal tachyarrhythmias which are resistant to other drugs or life-threatening. If amiodarone is used during gestation, a careful fetal/neonatal evaluation of thyroid function and morphology is warranted. It seems prudent to advise that fetal/neonatal hypothyroidism be treated, as soon as the diagnosis is made, even in utero, to avoid neurodevelopment abnormalities, although the latter may occur independently of hypothyroidism. If breast-feeding is allowed, careful evaluation of the infant's thyroid function and morphology is required because of the continuing exposure of the infant to the drug.

Drug therapy for hyperthyroidism in pregnancy: safety issues for mother and fetus

Hyperthyroidism (thyrotoxicosis) in pregnancy and the child bearing years is usually attributable to Graves' disease. This is an autoimmune condition in which thyroid-stimulating immunoglobulins (TSI) cause hyperthyroidism. As a rule, pregnancy complicates the management of hyperthyroidism, rather than vice versa. However, patients who remain thyrotoxic during pregnancy are at increased risk of maternal and fetal complications, particularly miscarriage and stillbirth. Therefore, bodyweight loss, eye signs and a bruit over the thyroid gland in a pregnant woman warrant thyroid investigation. Investigations should include measurement of serum free thyroid hormone levels [free thyroxine (T4) and free triiodothyronine (T3)] rather than total T4 and T3 levels, because total T4 and T3 levels may be raised in euthyroid pregnancies due to the presence of increased levels of thyroxine binding globulin (TBG). By 20 weeks' gestational age, the fetal thyroid is fully responsive to TSI and to antithyroid drugs. Maternal T4 and T3 and thyrotropin pass across the placenta in small and decreasing amounts as gestation progresses, but thyrotropin releasing hormone, TSI, antithyroid drugs, iodides and beta-blockers are readily transferred to the fetus from the mother. Hyperthyroidism is usually treated throughout pregnancy with an antithyroid drug, preferably propylthiouracil. The smallest dose which controls the disease is given with careful monitoring of free T4 and T3 levels to minimise the risk of fetal hypothyroidism and goitre. Bilateral subtotal thyroidectomy may be an option for a small number of patients with hyperthyroidism in pregnancy.