Neonatal thyroid function after propylthiouracil therapy for maternal Graves' disease

Incidence of and Risk Factors for Neonatal Hypothyroidism Among Women with Graves' Disease Treated with Antithyroid Drugs Until Delivery

Background: The incidence of neonatal hypothyroidism among newborns born to mothers with Graves' disease (GD) who continued antithyroid drug (ATD) treatment until delivery has never been reported. Objective: Our primary objective was to investigate the incidence of neonatal hypothyroidism among newborns born to mothers with GD who were treated with ATD until delivery. Our secondary objective was to identify the cutoff ATD daily doses for neonatal hypothyroidism risk, based on maternal thyrotropin (TSH) receptor antibody (TRAb) levels. Methods: We conducted a retrospective cohort study. We included 305 pregnant women with GD who were treated with an ATD until delivery (63 treated with methimazole [MMI] and 242 treated with propylthiouracil [PTU]). Umbilical cord TSH, free thyroxine (fT4), and TRAb levels were measured at delivery, and we investigated the respective relationships between neonatal hypothyroidism at delivery and maternal fT4 levels, TRAb levels, and daily ATD doses during pregnancy. Neonatal hypothyroidism was diagnosed when the umbilical cord fT4 level was below the lower limit of the reference range. Results: The incidence of neonatal hypothyroidism at delivery was 19.0% ([confidence interval, CI, 11.2-30.4]; 12/63) in the MMI group and 12.8% ([CI, 9.2-17.6]; 31/242) in the PTU group. Neonatal goiter was observed in one neonate in the PTU group, and two infants in the PTU group required levothyroxine treatment. The daily ATD dose in the third trimester was the strongest predictor of neonatal hypothyroidism at delivery; the cutoff MMI dose was 10 mg/day, and the cutoff PTU dose was 150 mg/day. When the maternal TRAb level in the third trimester was above three times the upper limit of the normal range, the cutoff MMI dose was 20 mg/day, and the cutoff PTU dose was 150 mg/day. Conclusions: Maternal fT4 and TRAb levels were higher in the neonatal hypothyroid group, which suggested prolonged GD activity. Careful follow-up is necessary when maternal GD remains active and the ATD dose to control maternal thyrotoxicosis cannot be reduced.

Dose-Dependent Influence of Antithyroid Drugs on the Difference in Free Thyroxine Levels between Mothers with Graves' Hyperthyroidism and Their Neonates

BACKGROUND

Several guidelines have recommended that the use of the lowest effective dose of antithyroid drugs (ATDs) that maintains maternal serum free thyroxine (FT4) levels at or moderately above the upper limit of the reference range is appropriate for fetal euthyroid status. However, little is known about whether ATD dosage affects the difference in serum FT4 levels between the mother and neonate. We conducted a retrospective study at a tertiary hospital in Japan to investigate the dose-dependent influence of ATDs on both maternal and fetal thyroid hormone status.

MATERIALS AND METHODS

We retrospectively examined 62 pregnant women who delivered between 2007 and 2016 and were treated for Graves' hyperthyroidism with ATD at any stage during pregnancy. We selected individuals whose data on maternal FT4 level within 4 weeks of their deliveries and cord FT4 level of their infants at the time of delivery were available. Those with multiple pregnancies, iodine or glucocorticoid treatment, and fetal goiter detected by ultrasonography were excluded.

RESULTS

After the exclusion criteria were applied, we recruited 40 individuals. The cord FT4 levels were significantly lower than the maternal FT4 levels in patients treated with high-dosage ATDs (methimazole >5 mg daily or propylthiouracil >100 mg daily). However, there were no significant differences between maternal and cord FT4 levels in patients treated with low-dosage ATDs (methimazole ≤5 mg daily or propylthiouracil ≤100 mg daily). We selected 35 individuals whose data on maternal thyrotropin receptor-binding inhibitory immunoglobulin (TBII) level were available. Multiple linear regression analysis adjusted for ATD dosage, maternal TBII level, and gestational period found that ATD dosage was a significant predictor of the difference in serum FT4 levels between the mother and neonate. In terms of maternal complications, multiple logistic regression analysis identified maternal free triiodothyronine (FT3) level as a significant predictor of the incidence of preterm delivery.

CONCLUSIONS

We found a dose-dependent influence of ATDs on the difference in serum FT4 levels between mothers with Graves' hyperthyroidism and their neonates. Further studies to evaluate the optimal target FT4 and FT3 levels for the mother and neonate during pregnancy may improve the outcome of pregnant women with Graves' hyperthyroidism.

Synergy between amyloid-β and tau in Alzheimer's disease

Patients with Alzheimer's disease (AD) present with both extracellular amyloid-β (Aβ) plaques and intracellular tau-containing neurofibrillary tangles in the brain. For many years, the prevailing view of AD pathogenesis has been that changes in Aβ precipitate the disease process and initiate a deleterious cascade involving tau pathology and neurodegeneration. Beyond this 'triggering' function, it has been typically presumed that Aβ and tau act independently and in the absence of specific interaction. However, accumulating evidence now suggests otherwise and contends that both pathologies have synergistic effects. This could not only help explain negative results from anti-Aβ clinical trials but also suggest that trials directed solely at tau may need to be reconsidered. Here, drawing from extensive human and disease model data, we highlight the latest evidence base pertaining to the complex Aβ-tau interaction and underscore its crucial importance to elucidating disease pathogenesis and the design of next-generation AD therapeutic trials.

Teratogen update: Antithyroid medications

OBJECTIVE

Thyroid disorders including hyperthyroidism are common during pregnancy. Untreated hyperthyroidism can result in adverse outcomes for pregnancy.

METHODS

Iodine, propylthiouracil (PTU), carbimazole (CMZ), and methimazole (MMI) are common medications for hyperthyroidism treatment. The literature regarding antithyroid medication use in pregnancy and breastfeeding is reviewed.

RESULTS

Animal studies for PTU have suggested congenital anomalies while animal studies for MMI have only indicated adverse outcomes at higher doses than used in humans. Epidemiological studies have noted an increased risk of congenital anomalies for PTU less often than CMZ or MMI but the epidemiological evidence remains mixed. A pattern of anomalies has been described for CMZ and MMI, from both case and epidemiological studies, including choanal atresia, aplasia cutis congenita, and other facial, heart, gastrointestinal, and skin anomalies. Closer examination of cases indicates that a few cases of the anomalies have occurred without exposure to CMZ or MMI and outside of the proposed critical period. PTU has a small risk of hepatotoxicity which rarely results in liver transplantation and death. Some authors have suggested that PTU be prescribed in early pregnancy and switched to MMI in late pregnancy. Untreated hyperthyroidism, from either a lack of medications or switching medications during the first trimester, may also increase the chance of congenital anomalies. Multiple case studies and larger epidemiological studies have failed to provide clear, consistent outcomes for the use of PTU, CMZ, and MMI in pregnancy. MMI and PTU both enter the breastmilk in small amounts.

CONCLUSION

Additional research is needed to assist in the medical management and exposure counseling of pregnant and breastfeeding women with hyperthyroidism.

Hyperthyroidism and Pregnancy

Clinical hyperthyroidism affects 0.1% to 0.4% of pregnancies. Gestational thyrotoxicosis is due to homology of the structure of TSH and HCG, which weakly stimulates the TSH receptor. Graves' disease (GD) most commonly causes clinically significant hyperthyroidism. Given concerns for teratogenicity from antithyroid drugs, these may be discontinued in low-risk GD patients. High-risk patients are treated with propylthiouracil in the first trimester then may transition to methimazole. Surgery is reserved for special circumstances; radioactive iodine is contraindicated. In late pregnancy, GD may remit; postpartum relapse is common. Measurement of serum thyrotropin receptor antibodies identifies pregnancies at-risk for fetal and neonatal hyperthyroidism.

Hyperthyroidism in the pregnant woman: Maternal and fetal aspects

Hyperthyroidism during pregnancy is uncommon. Nonetheless, prompt identification and adequate management of hyperthyroidism in a pregnant woman is essential, because uncontrolled thyrotoxicosis significantly increases the risk of maternal and fetal complications. Also, fetal prognosis may be affected by the transplacental passage of maternal thyroid stimulating antibodies or thyrostatic agents, both of which may disrupt fetal thyroid function. Birth defects have been reported in association with the use of antithyroid drugs during early pregnancy. Although rarely, offspring of mothers with Graves’ disease may develop fetal/neonatal hyperthyroidism, the management of which requires a close collaboration between endocrinologists, obstetricians, and neonatologists.

Because of the above considerations, the management of pregnant and lactating women with hyperthyroidism requires special care, bearing in mind that both maternal thyroid excess per se and related treatments may adversely affect the newborn’s health.

In this review we discuss the diagnosis and management of hyperthyroidism in pregnancy, along with the impact of thyrotoxicosis and medications on fetal outcome.

Hyperthyroidism During Pregnancy: Etiology, Diagnosis and Management

Pregnancy has marked effects on thyroid physiology and autoimmune thyroid disease tends to ameliorate through gestation due to the general immunosuppression seen in pregnancy. There is a need for trimester-specific thyroid hormone reference ranges. Hyperthyroidism in pregnancy – usually due to Graves' disease – is not common but, if the patient is compliant, a good outcome can be expected for both mother and child if treatment with anti-thyroid drugs (propylthiouracil is preferred) is instituted. Thyroid-stimulating hormone receptor antibody should be measured at 36 weeks in such patients in order to predict the possibility of neonatal hyperthyroidism. Transient gestational hyperthyroidism is often associated with hyperemesis gravidarum and thyroid function should be checked in patients severely affected by this condition. Radioiodine therapy is contraindicated in pregnancy but thyroid surgery may be performed safely in the second trimester. Autoimmune thyroiditis and Graves’ hyperthyroidism occur quite commonly in postpartum women.

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.

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.

Thermoregulatory deficits in adult Long Evans rat exposed perinatally to the antithyroidal drug, propylthiouracil

Developmental exposure to endocrine disrupting drugs and environmental toxicants has been shown to alter a variety of physiological processes in mature offspring. Body (core) temperature (T(c)) is a tightly regulated homeostatic system but is susceptible to disruptors of the hypothalamic pituitary thyroid (HPT) axis. We hypothesized that thermoregulation would be disrupted in adult offspring exposed perinatally to an HPT disruptor. Propylythiouracil (PTU) was used as a prototypical compound because of its well known antithyroidal properties. PTU was added to the drinking water of pregnant rats in concentrations of 0, 1, 2, 3, and 10 ppm from gestational day (GD) 6 through postnatal day (PND) 21. Adult male offspring were implanted with radiotransmitters to monitor Tc and motor activity (MA) and were observed undisturbed at an ambient temperature of 22 °C for 12 consecutive days. Data were averaged into a single 24 hour period to minimize impact of ultradian changes in T(c) and MA. All treatment groups showed a distinct circadian temperature rhythm. Rats exposed to 10 ppm PTU exhibited a marked deviation in their regulated T(c) with a reduction of approximately 0.4 °C below that of controls throughout the daytime period and a smaller reduction at night. Rats exposed to 1 or 2 ppm also had smaller but significant reductions in T(c). MA was unaffected by PTU. Overall, developmental exposure to moderate doses of an antithyroidal drug led to an apparent permanent reduction in T(c) of adult offspring that was independent of changes in MA.

Hyperthyroidism during pregnancy: etiology, diagnosis and management

Pregnancy has marked effects on thyroid physiology and autoimmune thyroid disease tends to ameliorate through gestation due to the general immunosuppression seen in pregnancy. There is a need for trimester-specific thyroid hormone reference ranges. Hyperthyroidism in pregnancy - usually due to Graves' disease - is not common but, if the patient is compliant, a good outcome can be expected for both mother and child if treatment with anti-thyroid drugs (propylthiouracil is preferred) is instituted. Thyroid-stimulating hormone receptor antibody should be measured at 36 weeks in such patients in order to predict the possibility of neonatal hyperthyroidism. Transient gestational hyperthyroidism is often associated with hyperemesis gravidarum and thyroid function should be checked in patients severely affected by this condition. Radioiodine therapy is contraindicated in pregnancy but thyroid surgery may be performed safely in the second trimester. Autoimmune thyroiditis and Graves' hyperthyroidism occur quite commonly in postpartum women.

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.

The effects of short-term manipulation of thyroid hormone status coinciding with primary wool follicle development on fleece characteristics in Merino sheep

Thyroidectomy surgery performed late in gestation results in perturbations in wool follicle development in foetal sheep, showing the importance of thyroid hormones for wool follicle development. The aim of this study was to determine the influence of transient manipulation of thyroid hormone status at a time corresponding with foetal primary wool follicle initiation. Pregnant Merino ewes (n = 12 per treatment) were treated daily between gestational days 55 and 64 with control (vehicle), exogenous thyroxine (T4) or propylthiouracil (PTU), an inhibitor of T4 synthesis, and conversion to the active form of the thyroid hormone (triiodothyronine). There were no significant differences in birth weight, gestational lengths and birth coat scores of the resultant lambs. The total primary and secondary follicle densities were significantly lower in lambs exposed to exogenous T4 compared with other treatments (P < 0.05). However, the T4 group displayed a higher proportion of mature secondary follicles (reflected by increased mature secondary follicle densities and mature secondary/primary follicle ratios) than the other treatment groups (P < 0.05). The skin morphology of the lambs differed 12 months later, with the T4 group having significantly higher total follicle densities compared with the PTU group, largely attributed to increased mature and total secondary follicle densities. However, this increase in wool follicle densities did not translate to differences in the fleece yields and weight, fibre diameter, staple lengths or any other fibre parameters. This study showed that transient manipulation of thyroid hormone status during foetal primary follicle initiation does have long-term consequences on the morphology of wool follicles, in particular the maturity of secondary wool follicles.

Thyroid disease in pregnancy

Thyroid diseases are common in women of childbearing age and it is well known that untreated thyroid disturbances result in an increased rate of adverse events, particularly miscarriage, preterm birth and gestational hypertension. Furthermore, thyroid autoimmunity per se seems to be associated with complications such as miscarriage and preterm delivery. While strong evidence clearly demonstrates that overt dysfunctions (hyper- or hypothyroidism) have deleterious effects on pregnancy, subclinical disease, namely subclinical hypothyroidism, has still to be conclusively defined as a risk factor for adverse outcomes. Additionally, other conditions, such as isolated hypothyroxinemia and thyroid autoimmunity in euthyroidism, are still clouded with uncertainty regarding the need for substitutive treatment.

Antithyroid drug-induced fetal goitrous hypothyroidism

Maternal overtreatment with antithyroid drugs can induce fetal goitrous hypothyroidism. This condition can have a critical effect on pregnancy outcome, as well as on fetal growth and neurological development. The purpose of this Review is to clarify if and how fetal goitrous hypothyroidism can be prevented, and how to react when prevention has failed. Understanding the importance of pregnancy-related changes in maternal thyroid status when treating a pregnant woman is crucial to preventing fetal goitrous hypothyroidism. Maternal levels of free T(4) are the most consistent indication of maternal and fetal thyroid status. In patients with fetal goitrous hypothyroidism, intra-amniotic levothyroxine injections improve fetal outcome. The best way to avoid maternal overtreatment with antithyroid drugs is to monitor closely the maternal thyroid status, especially estimates of free T(4) levels.

Toxicological considerations for antithyroid drugs in children

INTRODUCTION

Propylthiouracil (PTU), methimazole (MMI) and carbimazole are indicated for the treatment of hyperthyroidism in adult and pediatric patients. The aim of this review is to present all the relevant information regarding the use of antithyroid drugs (ATD) in pediatric thyrotoxic cases, the pediatric toxicology of ATD and the warning which has recently been issued for PTU by the FDA.

AREAS COVERED

Epidemiology, diagnosis and treatment of pediatric thyrotoxicosis are all presented in this article. The authors also extensively discuss the details regarding the pharmacology, bioactivation, biodisposition, bioavailability and pharmacokinetic properties of the two main ATD (MMI and PTU).

EXPERT OPINION

The FDA recently reported that use of PTU is associated with a higher risk for clinically serious or fatal liver injury compared to MMI in both adult and pediatric patients. They also found that congenital malformations were reported approximately three times more often with prenatal exposure to MMI compared with PTU and especially with the use of MMI during the first trimester of pregnancy. The authors believe that PTU should not be used in pediatric patients unless the patient is allergic to or intolerant of MMI, and there are no other treatment options available. That being said, PTU may be the treatment of choice during, and just before, the first trimester of pregnancy.

Aplasia cutis congenita in surviving co-twin after propylthiouracil exposure in utero

AIM

Aplasia cutis congenita (ACC) has been observed after fetal exposure to the antithyroid drug methimazole (MMI), but not reported after propylthiouracil (PTU), the current antithyroid drug of choice during pregnancy. This occurrence has implications for patient information and causal research.

CASE REPORT

We describe a surviving term co-twin to a mother with hyperthyroidism exposed to PTU from conception to 34 weeks of gestation presenting with ACC at birth.

DISCUSSION

The association between PTU exposure and ACC is clinically relevant and allows speculation on the etiology. A similar mechanism to the classical MMI-induced ACC is postulated, unless a vascular etiology suggested by a vanishing twin or maternal hyperthyroidism itself is causal. Coincidence of PTU exposure and ACC seems unlikely.

CONCLUSION

ACC in a newborn after PTU exposure during pregnancy hitherto observed only after MMI strongly encourages further reports of similar cases that may remain clinically underdiagnosed or unreported. Such confirmation could have significant implications for maternal treatment of hyperthyroidism, common in women of childbearing age.

Pregnancy outcome, thyroid dysfunction and fetal goitre after in utero exposure to propylthiouracil: a controlled cohort study

AIMS

Propylthiouracil (PTU) is presently considered to be the treatment of choice for hyperthyroidism in pregnancy. It is known to cross the human placenta, and therefore may affect the fetus. The major aims of this study were to evaluate the rate of major anomalies and to report the rate of fetal goitre, accompanied by hypothyroidism, in fetuses/ newborns of mothers after in utero exposure to PTU.

METHODS

Prospective observational controlled cohort study of PTU-exposed pregnancies of women counselled by the Israeli Teratology Information Service between the years 1994 and 2004 compared with women exposed to nonteratogens.

RESULTS

We followed up 115 PTU-exposed pregnancies and 1141 controls. The rate of major anomalies was comparable between the groups [PTU 1/80 (1.3%), control 34/1066 (3.2%), P= 0.507]. Hypothyroidism was found in 9.5% of fetuses/neonates (56.8% of whom with goitre). Hyperthyroidism, possibly resulting from maternal disease, was found in 10.3%. Goitres prenatally diagnosed by ultrasound were successfully treated in utero by maternal dose adjustment. In most cases neonatal thyroid functions normalized during the first month of life without any treatment. Median neonatal birth weight was lower [PTU 3145 g (2655-3537) vs. control 3300 g (2968-3600), P= 0.018].

CONCLUSIONS

PTU does not seem to be a major human teratogen. However, it could cause fetal/neonatal hypothyroidism with or without goitre. Fetal thyroid size monitoring and neonatal thyroid function tests are important for appropriate prevention and treatment.

Graves hyperthyroidism and pregnancy: a clinical update

OBJECTIVE

To provide a clinical update on Graves' hyperthyroidism and pregnancy with a focus on treatment with antithyroid drugs.

METHODS

We searched the English-language literature for studies published between 1929 and 2009 related to management of hyperthyroidism in pregnancy. In this review, we discuss differential diagnosis of hyperthyroidism, management, importance of early diagnosis, and importance of achieving proper control to avoid maternal and fetal complications.

RESULTS

Diagnosing hyperthyroidism during pregnancy can be challenging because many of the signs and symptoms are similar to normal physiologic changes that occur in pregnancy. Patients with Graves disease require prompt treatment with antithyroid drugs and should undergo frequent monitoring for signs of fetal and maternal hyperthyroidism and hypothyroidism. Rates of maternal and perinatal complications are directly related to control of hyperthyroidism in the mother. Thyroid receptor antibodies should be assessed in all women with hyperthyroidism to help predict and reduce the risk of fetal or neonatal hyperthyroidism or hypothyroidism. The maternal thyroxine level should be kept in the upper third of the reference range or just above normal, using the lowest possible antithyroid drug dosage. Hyperthyroidism may recur in the postpartum period as Graves disease or postpartum thyroiditis; thus, it is prudent to evaluate thyroid function 6 weeks after delivery. Preconception counseling, a multidisciplinary approach to care, and patient education regarding potential maternal and fetal complications that can occur with different types of treatment are important.

CONCLUSION

Preconception counseling and a multifaceted approach to care by the endocrinologist and the obstetric team are imperative for a successful pregnancy in women with Graves hyperthyroidism.

Management of Graves' hyperthyroidism in pregnancy: focus on both maternal and foetal thyroid function, and caution against surgical thyroidectomy in pregnancy

Graves' disease is a common autoimmune disorder in women in fertile ages. The hyperthyroidism is caused by generation of TSH-receptor activating antibodies. In pregnancy both the antibodies and the antithyroid medication given to the mother pass the placenta and affect the foetal thyroid gland. Thyroid function should be controlled not only in the mother with Graves' hyperthyroidism but also in her foetus.The review includes two cases illustrating some of the problems in managing Graves' disease in pregnancy. Major threats to optimal foetal thyroid function are inadequate or over aggressive antithyroid drug therapy of the mother. It should be taken into account that antithyroid drugs tend to block the foetal thyroid function more effectively than the maternal thyroid function, and that levothyroxin (L-T(4)) given to the mother will have only a limited effect in the foetus. Surgical thyroidectomy of patients with Graves' hyperthyroidism does not lead to immediate remission of the autoimmune abnormality, and the combination thyroidectomy+withdrawal of antithyroid medication+L-T(4) replacement of the mother involves a high risk of foetal hyperthyroidism. Conclusion Antithyroid drug therapy of pregnant women with Graves' hyperthyroidism should be balanced to control both maternal and foetal thyroid function. Surgical thyroidectomy of a pregnant woman with active disease may lead to isolated foetal hyperthyroidism.

Choanal atresia associated with maternal hyperthyroidism treated with methimazole: a case-control study

Thyrotoxicosis affects 0.2% of pregnant women and antithyroid drugs are the treatment of choice during pregnancy. Several case reports have suggested a relationship between the prenatal use of methimazole (MMI) and choanal atresia in the offspring. However, two epidemiological studies did not find an increased teratogenic risk for MMI. This multicenter case-control study compared the frequency of maternal hyperthyroidism treated with MMI during pregnancy, in children with choanal atresia (cases) and a control group randomly selected (three matched controls according to maternal age for each case). Mothers of cases (N = 61) and controls (N = 183) were interviewed for socio-demographic questions, obstetrical and genetic history, and exposure during pregnancy to different agents; specifically detailed information regarding hyperthyroidism and MMI intake was obtained. Prenatal exposure to maternal hyperthyroidism treated with MMI was identified in 10/61 cases (16.4%) compared to 2/183 (1.1%) in the control group (OR = 17.75; CI95% = 3.49-121.40). Cases and controls did not differ in their parental degree of education, paternal occupation, twinning, maternal parity, and other exposures during pregnancy. Facial features in exposed cases showed some similarities. Our data suggest that prenatal exposure to maternal hyperthyroidism treated with MMI is associated with choanal atresia. In addition, based on our cases and a critical literature review, we propose that the mother's disease might be the causal factor and not the MMI treatment.

Therapy Insight: management of Graves' disease during pregnancy

The diagnosis of Graves' disease in pregnancy can be complex because of normal gravid physiologic changes in thyroid hormone metabolism. Mothers with active Graves' disease should be treated with antithyroid drugs, which impact both maternal and fetal thyroid function. Optimally, the lowest possible dose should be used to maintain maternal free thyroxine levels at or just above the upper limit of the normal nonpregnant reference range. Fetal thyroid function depends on the balance between the transplacental passage of thyroid-stimulating maternal antibodies and thyroid-inhibiting antithyroid drugs. Elevated levels of serum maternal anti-TSH-receptor antibodies early in the third trimester are a risk factor for fetal hyperthyroidism and should prompt evaluation of the fetal thyroid by ultrasound, even in women with previously ablated Graves' disease. Maternal antithyroid medication can be modulated to treat fetal hyperthyroidism. Serum TSH and either total or free thyroxine levels should be measured in fetal cord blood at delivery in women with active Graves' disease, and those with a history of (131)I-mediated thyroid ablation or thyroidectomy who have anti-TSH-receptor antibodies. Neonatal thyrotoxicosis can occur in the first few days of life after clearance of maternal antithyroid drug, and can last for several months, until maternal antibodies are also cleared.

The safety and efficacy of antithyroid drugs

Thionamides, selective inhibitors of thyroid peroxidase-mediated iodination by tyrosine residues in thyroglobulin, have been effectively used in the treatment of hyperthyroidism. The choices for initial treatment of patients with Graves' disease differ in various countries, and many physicians around the world prefer to administer thionamide drugs as the first choice of treatment for patients with hyperthyroidism. Although some thyroidologists more often consider radioiodine to be the treatment of choice because of its safety and ease of administration, thionamides remain the mainstay of treatment in thyrotoxic children and adolescents and in hyperthyroid women during pregnancy, postpartum period and lactation. A recent study with continuous thionamide treatment for patients with Graves' disease shows its efficacy, safety and cost-benefit properties. Further studies of the effectiveness of continuous thionamide therapy in patients with thyrotoxicosis need to be designed and implemented to determine indications for such therapy in children, adolescents and adults with diffuse toxic goiter, in particular, in those who have had recurrence of hyperthyroidism after discontinuation of one complete course of treatment.

Management of Graves' disease during pregnancy: the key role of fetal thyroid gland monitoring

BACKGROUND

Fetuses from mothers with Graves' disease may experience hypothyroidism or hyperthyroidism due to transplacental transfer of antithyroid drugs (ATD) or anti-TSH receptor antibodies, respectively. Little is known about the fetal consequences. Early diagnosis is essential to successful management. We investigated a new approach to the fetal diagnosis of thyroid dysfunction and validated the usefulness of fetal thyroid ultrasonograms.

METHODS

Seventy-two mothers with past or present Graves' disease and their fetuses were monitored monthly from 22 wk gestation. Fetal thyroid size and Doppler signals, and fetal bone maturation were determined on ultrasonograms, and thyroid function was evaluated at birth. Thyroid function and ATD dosage were monitored in the mothers.

RESULTS

The 31 fetuses whose mothers were anti-TSH receptor antibody negative and took no ATDs during late pregnancy had normal test results. Of the 41 other fetuses, 30 had normal test results at 32 wk, 29 were euthyroid at birth, and one had moderate hypothyroidism on cord blood tests. In the remaining 11 fetuses, goiter was visualized by ultrasonography at 32 wk, and fetal thyroid dysfunction was diagnosed and treated; there was one death, in a late referral, and 10 good outcomes with normal or slightly altered thyroid function at birth. The sensitivity and specificity of fetal thyroid ultrasound at 32 wk for the diagnosis of clinically relevant fetal thyroid dysfunction were 92 and 100%, respectively.

CONCLUSION

In pregnant women with past or current Graves' disease, ultrasonography of the fetal thyroid gland by an experienced ultrasonographer is an excellent diagnostic tool. This tool in conjunction with close teamwork among internists, endocrinologists, obstetricians, echographists, and pediatricians can ensure normal fetal thyroid function.

Thyroid disorders and pregnancy

During pregnancy physiologic changes in thyroid function occur which should not be misinterpreted as pathological. Thyroid disorders may complicate pregnancy and need thorough investigation and treatment in order to ensure a favourable pregnancy outcome. The incidence of hyperthyroidism in pregnant women has been reported to be approximately 0.2%. The leading cause is Graves' disease. Treatment of hyperthyroidism includes antithyroid drugs or surgery to avoid adverse effects on the neonate such as prematurity, intrauterine growth retardation and fetal or neonatal thyrotoxicosis. Use of radioactive iodine is contraindicated. Hypothyroidism during pregnancy is associated with gestational hypertension and low birth weight. Women on thyroid replacement therapy before pregnancy may require an increase in dosage during pregnancy. Pregnant women with chronic autoimmune thyroiditis have a higher incidence of spontaneous miscarriage. Nodular disease demands meticulous investigation to rule out a toxic adenoma or malignancy. Surgery in the case of cancer can be postponed under certain circumstances. Within one year following delivery, about 5-10% of women may exhibit postpartum autoimmune thyroid dysfunction, which may result in hypothyroidism.

Autoimmune thyroid disease in pregnant women and their offspring

OBJECTIVE

To present an overview of autoimmune thyroid disease (AITD) that can occur in pregnancy.

METHODS

The major thyroid antibodies that can traverse the maternal-fetal circulation and affect the fetus are summarized, those women at risk of having affected fetuses are identified, and the diagnosis, course, and treatment of AITD in maternal and neonatal patients are discussed.

SUMMARY

AITD, including Graves' disease and autoimmune thyroiditis, is common in women of childbearing age. Rarely, the fetus can be affected because of transplacental passage of maternal IgG. Of the thyroid autoantibodies found in AITD, only those directed against the thyroid-stimulating hormone (TSH) receptor have been shown to cause fetal thyroid dysfunction. Both transient neonatal hyperthyroidism and hypothyroidism have been described, as has delayed onset of neonatal hyperthyroidism due to the coexistence of stimulating and blocking TSH receptor antibodies. In general, affected infants are those born to mothers with the most potent antibody activity, and the duration of the neonatal thyroid dysfunction is dependent on the antibody titer and the rate of metabolic clearance from the infant's circulation. If fetal hyperthyroidism is suspected, maternal TSH receptor antibodies should be measured during the third trimester of pregnancy. For neonatal hypothyroidism, this measurement in the mother or baby soon after birth will suffice. Screening for the presence of TSH receptor antibodies by radioreceptor assay is the most cost-effective approach. If results are positive, bioassay should be done to determine the nature of the antibody activity. Women at risk of having babies with neonatal hyperthyroidism include those with a history of previous affected infants, with difficult to control thyrotoxicosis, or with a history of Graves' disease and development of hypothyroidism either spontaneously or as a result of thyroid gland ablation. Transient neonatal hypothyroidism due to TSH receptor-blocking antibodies should be suspected in any infant with hypothyroidism born to a mother with AITD (particularly those with previously affected offspring).

CONCLUSION

Treatment of maternal hyperthyroidism must consider both maternal and fetal thyroid status. In general, the lowest dose of antithyroid medication sufficient to produce maternal euthyroidism or slight hyperthyroidism is used. In pregnant women with hypothyroidism, doses of L-thyroxine should be sufficient to normalize maternal thyroid function without regard to the fetus. Identification and treatment of affected infants soon after birth will ensure a normal outcome. Whether inadequately treated maternal hypothyroidism is associated with a permanent intellectual deficit in the offspring is currently unknown.

Contribution of genetic factors to neonatal transient hypothyroidism

BACKGROUND

The causes of neonatal transient hypothyroidism (NTH) remain incompletely understood. Whether it is influenced by genetic background is rarely discussed and remains unproven. A defect in thyroid peroxidase is a common cause of dyshormonogenesis of the thyroid gland in Taiwanese, with a novel mutation (2268insT) present in nearly 90% of alleles studied.

OBJECTIVE

To determine if the presence of this common mutation is associated with NTH in Taiwan.

METHODS

A mismatched primer was designed and used for this specific 2268insT mutation to screen 1000 normal babies and 260 babies with confirmed NTH.

RESULTS

The carrier rate for 2268insT in normal babies (1/200) was significantly lower than in babies with NTH (1/13; p<0.0001).

CONCLUSIONS

The results strongly suggest that the presence of this thyroid peroxidase mutation contributes to the development of NTH. Likely pathogenetic explanations include the effect of the stress of extrauterine adaptation during labour on an immature pituitary-thyroid axis in genetically predisposed individuals, combined with environmental triggers such as iodine deficiency, perinatal iodine exposure, and/or goitrogen contamination.

Transient hypothyroidism or persistent hyperthyrotropinemia in neonates born to mothers with excessive iodine intake

Perinatal exposure to excess iodine can lead to transient hypothyroidism in the newborn. In Japan, large quantities of iodine-rich seaweed such as kombu (Laminaria japonica) are consumed. However, effects of iodine from food consumed during the perinatal period are unknown. The concentration of iodine in serum, urine, and breast milk in addition to thyrotropin (TSH), free thyroxine (FT(4)), and thyroglobulin was measured in 34 infants who were positive at congenital hypothyroidism screening. Based on the concentration of iodine in the urine, 15 infants were diagnosed with hyperthyrotropinemia caused by the excess ingestion of iodine by their mothers during their pregnancy. According to serum iodine concentrations, these infants were classified into group A (over 17 microg/dL) and group B (under 17 microg/dL) of serum iodine. During their pregnancies these mothers consumed kombu, other seaweeds, and instant kombu soups containing a high level of iodine. It was calculated that the mothers of group A infants ingested approximately 2300-3200 microg of iodine, and the mothers of group B infants approximately 820-1400 microg of iodine per day during their pregnancies. Twelve of 15 infants have required levo-thyroxine (LT(4)) because hypothyroxinemia or persistent hyperthyrotropinemia was present. In addition, consumption of iodine by the postnatal child and susceptibility to the inhibitory effect of iodine may contribute in part to the persistent hyperthyrotropinemia. We propose that hyperthyrotropinemia related to excessive iodine ingestion by the mother during pregnancy in some cases may not be transient.

Hyperthyroidism in pregnancy

Graves' disease may complicate the course of pregnancy; pregnancy on the other hand may alter the natural course of the disease. It is imperative for women of childbearing age affected by the disease to be informed about the potential maternal and fetal problems if the condition is not properly managed. Preconception control in women with diabetes has resulted in a dramatic decrease in the number of perinatal complications. The same approach should be encouraged for women with thyroid diseases. Ideally, the women suffering from hyperthyroidism or any other thyroid disease should be metabolically compensated at time of conception-the need for contraception until the disease is controlled should be openly discussed. A multidisciplinary approach by a health care team is of paramount importance during pregnancy, with the involvement of the obstetrician, perinatologist, endocrinologist, neonatologist, pediatrician and anesthesiologist. In many situations the assistance of social workers, nutritionists, and other health care professionals may be needed. The future mother and her family should be aware of the potential complications for both mother and her offspring if proper management guidelines are not carefully followed.

Fetal hydrops, associated with maternal propylthiouracil exposure, reversed by intrauterine therapy

Thyroid hormone is essential for fetal neurological development. Among other etiologies, fetal hypothyroidism may be caused by maternal exposure to antithyroid drugs (ATDs). The most common presentation of fetal hypothyroidism is fetal goiter, which can cause dystocia, in addition to airway obstruction in the neonate. Intra-amniotic treatment with levothyroxine normalizes fetal thyroid status and reduces goiter size. We present a case of fetal hypothyroidism diagnosed in a patient who was treated with propylthiouracil (PTU) for Grave's disease. The fetus had marked hydrops fetalis and a large goiter. In addition, anal stenosis, vesicovaginal fistula, bilateral pyelectasia and polydactyly were diagnosed in the neonate. Intra-amniotic treatment with levothyroxine resulted in a regression of the hydrops and a reduction in the goiter size. A euthyroid, non-edematous, non-goitrous neonate was delivered. At the age of 27 months the child's psychomotor development was normal. The present case indicates that hydrops fetalis may be an unusual manifestation of fetal hypothyroidism, caused by intrauterine exposure to maternal antithyroid drugs (ATDs), and that it may be resolved by treatment with intra-amniotic levothyroxine.

Management of hypo- and hyperthyroidism during pregnancy

Pregnancy has profound effects on the regulation of thyroid function, and on thyroidal functional disorders, that need to be recognized, carefully assessed and correctly managed. Relative hypothyroxinemia and goitrogenesis may occur in healthy women who reside in areas with restricted iodine intake, strongly suggesting that pregnancy constitutes a stimulatory challenge for the thyroid. Overt thyroid dysfunction occurs in 1-2% of pregnant women, but mild forms of dysfunction (both hyper- and hypothyroidism) are probably more prevalent and frequently remain unrecognized. Alterations of maternal thyroid function have important implications for fetal and neonatal development. In recent years, particular attention has been drawn to the potential risks for the developing fetus due to maternal hypothyroxinemia during early gestation. Concerning hyperthyroidism, the two main causes of thyrotoxicosis in the pregnant state are Graves' disease and gestational transient thyrotoxicosis (GTT). The natural history of Graves' disease is altered during pregnancy, with a tendency for exacerbation during the first trimester, and amelioration during the second and third trimesters. The natural history of the disorder must be considered when treating patients, since antithyroid drugs cross the placenta and can directly affect fetal thyroid function. Algorithms to routinely screen pregnant women for thyroid dysfunction have been proposed in recent years, but these have not yet been implemented systematically, nor have they been the subject of cost-effectiveness analyses.

Prescription drugs and pregnancy

Prescribing drugs in pregnancy is an unusual risk-benefit situation. Drugs that may be of benefit or even life-saving to the mother can deform or kill the fetus. However, the risk to the fetus should not be exaggerated. There are only approximately 20 drugs or groups of drugs which are known to cause birth defects in humans. For one of these drugs to cause birth defects, a number of criteria must be fulfilled. The drug exposure must take place at a critical stage of pregnancy and the dose must be high enough to cause a threshold of exposure for an appropriate duration of time. For most of the known human teratogens, > 90% of pregnancies exposed during the first trimester result in normal offspring. Although only a few drugs are known to cause birth defects in humans, uncertainty about the safety of the majority may lead to underprescribing for pregnant women and women of childbearing age. Epidemiological studies of pregnancy outcome after specific drug exposures are often superficially reassuring, but most are severely limited in their power to detect adverse outcomes. Safety in animal studies may also be reassuring but species differences demand caution in this interpretation. Concerns about prescription drugs in the first trimester, when they can cause birth defects, are mostly quite different to concerns about use in the second and third trimesters. As the fetal organ systems mature, the fetus can be affected by the pharmacological activity of the drug in the same way as the mother. Many drugs have pharmacological effects on the fetus in the second and third trimesters but in most cases, they are well recognised and can be managed or avoided. The material presented in this paper is mostly concerned with the 'risks' associated with drugs in pregnancy. No attempt has been made to quantitate the possible benefits to the mother or fetus. Communicating the risk-benefit situation to the patient is always a challenge for physicians with limited time and sometimes limited knowledge. Fear of litigation is an unfortunate and an unwanted parameter in the assessment. Better knowledge of the parameters that determine teratogenicity may allow physicians to feel more confident in assessing the risks and benefits associated with prescribing in pregnancy.

Postpartum recurrence of Graves' hyperthyroidism can be prevented by the continuation of antithyroid drugs during pregnancy

OBJECTIVE

Previous studies recommend the discontinuation of antithyroid drug (ATD) therapy during pregnancy in women with well-controlled Graves' hyperthyroidism (GH). In this study, we investigated whether this termination of ATD therapy during pregnancy is beneficial in terms of postpartum GH recurrence.

DESIGN

A nonrandomized, retrospective study.

PATIENTS

Sixty-five pregnant GH patients treated with maintenance doses of ATDs were assigned into two groups: ATD therapy was discontinued before delivery in Group 1, but continued during pregnancy and after delivery in Group 2.

MEASUREMENTS

The prevalence of postpartum recurrence or exacerbation of GH within 1 year after delivery was examined. Serum T4, T3 TSH, and TSH receptor antibody levels were measured.

RESULTS

In Group 1, 70.8% (17/24) of patients suffered a recurrence of GH within 1 year after delivery. In contrast, a postpartum exacerbation of GH was observed in only 29% (12/41) of patients in Group 2 (P < 0.01). Both exacerbations and recurrences of GH appeared primarily within 4-6 months after delivery. Apparent neonatal hypothyroidism and malformations were not observed in the offspring of either group.

CONCLUSION

Continuing antithyroid drug therapy throughout pregnancy prevents postpartum recurrence of Graves' hyperthyroidism without resulting in neonatal hypothyroidism or malformations.

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.

Rapid resolution of fetal goiter associated with maternal Grave's disease: a case report

The incidence of abnormal fetal thyroid function with maternal Grave's disease is about 2-12%. The development of larger fetal goiters can complicate labor and precipitate life-threatening airway obstruction at delivery. A case is presented of a large stable goiter confirmed by sonography, which unexpectedly resolved by the time of parturition. A 3 x 6 cm fetal goiter was detected at 34 weeks gestation in a mother treated with propylthiouracil for Grave's disease. A repeat sonogram at 36 weeks showed no change in goiter size. Umbilical blood sampling showed the fetus to be markedly hyperthyroid. Planned Cesarean section took place 11 days after the final sonogram. A multi-disciplinary operative team was present including the Otolaryngology service with equipment for emergency intubation, bronchoscopy and tracheotomy. Upon delivery, the infant had no evidence of goiter and no airway compromise. Fetal goiter is a rare entity, and recent advances in the field of maternal-fetal medicine have enabled intra-uterine diagnosis and treatment of such conditions. A review of published case reports demonstrates two trends in treated fetuses: preterm progressive resolution of the goiter, or delivery with gross evidence of goiter. This reported case is unique, as a persistent goiter resolved completely in less than 2 weeks. Otolaryngologic response to and management of potential congenital airway compromise is discussed.

Circadian rise in maternal glucocorticoid prevents pulmonary dysplasia in fetal mice with adrenal insufficiency

The hypothalamic-pituitary-adrenal (HPA) axis, including hypothalamic corticotropin-releasing hormone (CRH) and pituitary corticotropin, is one of the first endocrine systems to develop during fetal life, probably because glucocorticoid secretion is necessary for the maturation of many essential fetal organs. Consistent with this, pregnant mice with an inactivating mutation in the Crh gene deliver CRH-deficient offspring that die at birth with dysplastic lungs, which can be prevented by prenatal maternal glucocorticoid treatment. But children lacking the ability to synthesize cortisol (because of various genetic defects in adrenal gland development or steroidogenesis) are not born with respiratory insufficiency or abnormal lung development, suggesting that the transfer of maternal glucocorticoid across the placenta might promote fetal organ maturation in the absence of fetal glucocorticoid production. We used pregnant mice with a normal HPA axis carrying fetuses with CRH deficiency to characterize the relative contributions of the fetal and maternal adrenal to the activity of the fetal HPA axis, and related these findings to fetal lung development. We found that in the presence of fetal adrenal insufficiency, normal fetal lung development is maintained by the transfer of maternal glucocorticoid to the fetus, specifically during the circadian peak in maternal glucocorticoid secretion.

Fetal and neonatal hyperthyroidism

Fetal and neonatal hyperthyroidism are usually produced by transplacental passage of thyroid-stimulating immunoglobulins. Most commonly, the thyroid-stimulating immunoglobulins are a component of active maternal Graves' disease. However, such antibodies may continue to be produced after ablation of the thyroid by surgery, radioiodine, or by the immune mechanisms of Hashimoto's thyroiditis. Other mechanisms that have produced fetal and neonatal hyperthyroidism include activating mutations of the stimulatory G protein in McCune-Albright syndrome and activating mutations of the thyrotropin (TSH) receptor. Fetal hyperthyroidism may be associated with intrauterine growth retardation, nonimmune fetal hydrops, craniosynostosis, and intrauterine death. Features of this condition in the neonate include hyperkinesis, diarrhea, poor weight gain, vomiting, ophthalmopathy, cardiac failure and arrhythmias, systemic and pulmonary hypertension, hepatosplenomegaly, jaundice, hyperviscosity syndrome, thrombocytopenia, and craniosynostosis. The time course of thyrotoxicosis depends on etiology. Remission by 20 weeks is most common in neonatal Graves' disease; remission by 48 weeks is nearly always seen. A subset of these patients may have persistent disease when there is a strong family history of Graves' diseases. Disease persistence is characteristic of patients with activating mutations of the TSH receptor. Treatment of fetal hyperthyroidism comprises administration of antithyroid drugs to the mother. Fetal heart rate and fetal growth should be monitored. Ultrasonography may reveal changes in thyroid size. At times, cordocentesis may be useful for monitoring fetal thyroid function. Hyperthyroid neonates may be treated with antithyroid drugs, beta-adrenergic receptor blocking agents, iodine, or iodinated contrast agents, and at times, with glucocorticoids and digoxin. Nonremitting causes of neonatal hyperthyroidism require ablative treatments such as thyroidectomy.

Prenatal diagnosis of thyroid hormone resistance

A 29-yr-old woman with pituitary resistance to thyroid hormones (PRTH) was found to harbor a novel point mutation (T337A) on exon 9 of the thyroid hormone receptor beta (TRbeta) gene. She presented with symptoms and signs of hyperthyroidism and was successfully treated with 3,5,3'-triiodothyroacetic acid (TRIAC) until the onset of pregnancy. This therapy was then discontinued in order to prevent TRIAC, a compound that crosses the placental barrier, from exerting adverse effects on normal fetal development. However, as the patient showed a recurrence of thyrotoxic features after TRIAC withdrawal, we sought to verify, by means of genetic analysis and hormone measurements, whether the fetus was also affected by RTH, in order to rapidly reinstitute TRIAC therapy, which could potentially be beneficial to both the mother and fetus. At 17 weeks gestation, fetal DNA was extracted from chorionic villi and was used as a template for PCR and restriction analysis together with direct sequencing of the TRbeta gene. The results indicated that the fetus was also heterozygous for the T337A mutation. Accordingly, TRIAC treatment at a dose of 2.1 mg/day was restarted at 20 weeks gestation. The mother rapidly became euthyroid, and the fetus grew normally up to 24 weeks gestation. At 29 weeks gestation mild growth retardation and fetal goiter were observed, prompting cordocentesis. Circulating fetal TSH was very high (287 mU/L) with a markedly reduced TSH bioactivity (B/I: 1.1 +/- 0.4 vs 12.7 +/- 1.2), while fetal FT4 concentrations were normal (8.7 pmol/L; normal values in age-matched fetuses: 5-22 pmol/L). Fetal FT3 levels were raised (7.1 pmol/L; normal values in age-matched fetuses: <4 pmol/L), as a consequence of 100% cross-reactivity of TRIAC in the FT3 assay method. To reduce the extremely high circulating TSH levels and fetal goiter, the dose of TRIAC was increased to 3.5 mg/day. To monitor the possible intrauterine hypothyroidism, another cordocentesis was performed at 33 weeks gestation, showing that TSH levels were reduced by 50% (from 287 to 144 mU/L). Furthermore, a simultaneous ultrasound examination revealed a clear reduction in fetal goiter. After this latter cordocentesis, acute complications occured, prompting delivery by cesarean section. The female neonate was critically ill, with multiple-organ failure and respiratory distress syndrome. In addition, a small goiter and biochemical features ofhypothyroidism were noted transiently and probably related to the prematurity of the infant. At present, the baby is clinically euthyroid, without goiter, and only exhibits biochemical features of RTH. In summary, although further fetal studies in cases of RTH are necessary to determine whether elevated TSH levels with a markedly reduced bioactivity are a common finding, our data suggest transient biochemical hypothyroidism in RTH during fetal development. Furthermore, we advocate prenatal diagnosis of RTH and adequate treatment of the disease in case of maternal hyperthyroidism, to avoid fetal thyrotrope hyperplasia, reduce fetal goiter, and maintain maternal euthyroidism during pregnancy.

Thyroid disease in women

Thyroid diseases occur more commonly in women than men, in part because of the autoimmune nature of many thyroid disorders. Hypothyroidism, and thyroid nodules occur frequently in both pre- and postmenopausal women. Pregnancy is also associated with changes in thyroid function. The goal of this article is to review the current information on the pathophysiology and treatment of thyroid disorders which are common in women.

Treatment of thyroid disease in pregnancy

With appropriate therapy, complications related to thyroid disease in pregnancy can be minimized. Although the diagnosis of thyroid endocrinopathy may be difficult in pregnancy, few therapies are contra-indicated. Because medications may cross the placenta, however, clinicians need always to be mindful of potential fetal effects and should work to use the minimal dose necessary to achieve maternal euthyroidism. Thyroid function tests, in particular free T4 and TSH, remain good measures of thyroid function and therapy in pregnancy.

Prenatal treatment of fetal hypothyroidism: is there more than one option?

Following the diagnosis of fetal goitre at 22 and 24 weeks' gestation in two hyperthyroid pregnant women who underwent treatment with 400-500 mg of propylthiouracil in the first weeks of pregnancy, a total of seven fetal blood samplings were performed to evaluate thyroid function before and after the initiation of two different treatment regimens. L-Thyroxine (600 micrograms) was injected five times intra-amniotically in one woman and continuous maternal administration of the thyroid analogue 3, 5, 3'-triiodothyroacetic acid (Triac) was attempted in the other. Normalization of fetal thyroid function and reduction of fetal goitre were achieved in both fetuses and transplacental passage of Triac was indirectly demonstrated by high levels of free triiodothyronine in fetal blood. In cases of fetal hypothyroidism, direct or indirect prenatal therapy can be adopted successfully and safely.

In utero diagnosis and treatment of fetal goitrous hypothyroidism, caused by maternal use of propylthiouracil

A fetal goitre is a potentially dangerous phenomenon because of mechanical obstruction and possible fetal thyroid function disorders. In this report we describe a patient with Graves' disease diagnosed in early pregnancy and treated with propylthiouracil, which resulted in a large fetal goitre and fetal hypothyroidism. The diagnostic problems are discussed and we focus on the need for fetal thyroid hormone serum evaluation. The only reliable way to obtain information about the fetal thyroid status is percutaneous fetal umbilical cord blood sampling, since amniotic fluid levels do not properly represent the fetal thyroid function. Fetal hypothyroidism can thus be diagnosed in utero and treated with intra-amniotic injections of thyroxine. The recommended dose and frequency of injections are only based on a few case reports and for that reason we performed a second fetal blood sampling 1 week later to evaluate our therapy. Weekly intra-amniotic injections of 250 micrograms of thyroxine seem to be sufficient to reduce a fetal goitre and give a normal thyroid hormone level.

Fetal thyrotoxicosis: a case report and recommendations for prediction, diagnosis, and treatment

A maternal history of Graves' disease places the fetus at risk for thyrotoxicosis in utero via the placental transfer of thyroid-stimulating immunoglobulins. Methods for prediction of fetal hyperthyroidism are available, but are not widely used. Clinical assessment of fetal thyroid status by monitoring of fetal heart rate and growth may be inaccurate. This raises some uncertainty in the initial diagnosis of fetal thyrotoxicosis and complicates the assessment of fetal response to maternal propylthiouracil therapy. A case illustrating these pitfalls in the diagnosis and management of fetal hyperthyroidism is presented. The condition was correctly diagnosed, but treatment based on fetal heart rate resulted in biochemical hypothyroidism in the infant at birth. Current recommendations for diagnosis and treatment of fetal hyperthyroidism are reviewed along with recent developments in the field. A modified approach is proposed.