Lack of influence of thyroid antibodies on thyroid function in the newborn infant and on a mass screening program for congenital hypothyroidism

A literature review on the redundancy of additional thyroid function tests in neonates of mothers with hypothyroidism

AIM

Newborn thyroid screening tests are carried out during the first days after birth in many parts of the world. The aim of this review was to assess whether additional thyroid function tests of neonates born to mothers with hypothyroidism are necessary to diagnose newborns with congenital hypothyroidism (CH) missed by the usual screening test.

METHODS

A search in PubMed and Google Scholar databases was conducted for pertinent studies, using relevant keywords. All studies that were published in any language from 1 January 2000 to 30 June 2023 were included. Observational cohort studies were included in the analysis, while case reports and studies not referring to neonates were excluded.

RESULTS

Thirteen studies were identified comprising more than 4400 infants with CH. Studies with the larger study populations recommended against additional testing in healthy infants of hypothyroid mothers. Similar were the results of some smaller retrospective studies. Few studies identified in total 16 infants with CH that were missed on neonatal screening without, though, a definite causative link between the mother's and the infant's thyroid dysfunction.

CONCLUSION

Based on available data, additional thyroid function tests seem redundant in identifying undiagnosed cases of CH. Larger studies are needed to reach a definite conclusion.

Thyroid Autoimmunity in Adverse Fertility and Pregnancy Outcomes: Timing of Assisted Reproductive Technology in AITD Women

Thyroid autoimmunity (TAI) is prevalent in women of live-birthing age and has independently been associated with complications of fertility and pregnancy, in the case of spontaneous conception or after assisted reproductive technology (ART) treatment. However, it remains challenging to identify causation between infertility and TAI, even interventional trials looking at the impact of levothyroxine (LT4) treatment on fertility and pregnancy outcomes due to differences among study results which related to small scales, impropriate study designs, enrollment criteria of infertility cause and titer/hormone concentration measurements. Furthermore, many questions remain unsettled in ART management in AITD infertile women attempt pregnancy. Therefore, further observational and interventional trials are needed more comprehensive multiple-center, double blinded, and randomized.

Impact of maternal thyroid disease on neonatal thyroid status

OBJECTIVES

Prevalence of Maternal and congenital hypothyroidism is on the rise. To present the thyroid stimulating hormone screening results in babies born to hypothyroid mothers and assess the burden, aetiology of hypothyroidism in these babies.

METHODS

All antenatal mothers attending our hospital during the study period were enrolled into the study. Group I includes 249 term babies born to hypothyroid mothers and group II comprises 2154 newborns born to mothers who are euthyroid. Heel prick thyroid stimulating hormone was done for all newborns on day 3 for both groups. Confirmatory venous testing was done for all for babies in group I and screen positives belonging to group II. Evaluation and therapy done as per standard guidelines.

RESULTS

Thyroid stimulating hormone values in the two groups are presented. There was significant correlation between peak maternal thyroid stimulating hormone and neonatal day 3 heel prick in group I (r=0.7, P<0.05). The prevalence of positive screening test in groups I and II was 3.8 and 1.03% (p<0.05) whereas corresponding values for confirmed disease was 4.3 and 0.6%, respectively (p<0.05). Aetiological evaluation revealed both transient hypothyroidism (33.3%) and permanent hypothyroidism (66.6%).

CONCLUSION

4.3% of babies born to hypothyroid mothers develop congenital hypothyroidism; aetiology being both transient and permanent. A venous test by 3 weeks is helpful in these babies to improve case identification.

Follow-up of infants born to mothers with autoinmune thyroid disease. What should not be screened?

INTRODUCTION

Thyroid dysfunction is a common problem in pregnant women. It is usually of an autoimmune origin, with Hashimotós thyroiditis and Graveś disease being the most common conditions. Although hormonal changes and transplacental antibody transfer may occur, specific neonatal screening has not been shown to be useful.

PATIENTS AND METHOD

A prospective study of newborns of women with autoimmune thyroid disease born at a level III university hospital (November 2013-December 2016). Neonates were selected during their stay at the maternity. Babies with perinatal asphyxia were excluded. Data were collected from the clinical histories of mothers and newborns.

RESULTS

A total of 191 neonates were included. Ninety percent of mothers had been diagnosed with autoimmune hypothyroidism. Only 5.8% of newborns had some laboratory disorder, consisting of slightly increased thyroid-stimulating hormone levels, which returned to normal at the age of one month and did not correlate to thyroid peroxidase antibody levels. Transient hyperthyrotropinemia was diagnosed in one newborn and required thyroxin treatment during the first year of life. Among newborns from mothers with Graveś disease, 36.8% had some abnormal laboratory value during the first 7 days of life, but there were no cases of hyperthyroidism and only one of transient hyperthyrotropinemia.

CONCLUSIONS

Experience at our hospital in screening of newborns from hypothyroid mothers reveals a high number of laboratory controls with a poor diagnostic yield. No relationship was found between thyroid peroxidase antibody levels and thyroid dysfunction. We support the recommendations to continue testing serum thyroid-stimulating hormone and FT4 levels at 48h of life in newborns of mothers with autoimmune hypothyroidism.

Autoimmune thyroid disease during pregnancy

Understanding of changes in thyroid function and the consequences of thyroid disease during pregnancy has rapidly grown in the past two decades, and revised American Thyroid Association guidelines on this topic were published in 2017. This Review explores the association between thyroid autoimmunity and complications during and after pregnancy. Thyroid autoimmunity refers to the presence of antibodies to thyroperoxidase or thyroglobulin, or thyroid-stimulating hormone receptor antibodies (TRAbs), or a combination of these, and is present in up to 18% of pregnant women. Thyroid antibodies in pregnant women with normal functioning thyroids (ie, euthyroid) have been associated with several complications, including miscarriage and premature delivery. Treatments to improve pregnancy outcomes are being studied. Whether thyroid antibodies are associated with infertility and assisted reproductive technology outcomes is unclear; although, treatment with low doses of levothyroxine, which is usually used to treat hypothyroidism, can be considered in such situations. Additionally, thyroid antibodies have been associated with other neonatal and maternal complications. All these associations require confirmation in larger prospective studies, and their pathogenic mechanisms need to be better understood. Post-partum thyroiditis is substantially more frequent in women who have thyroid antibodies during pregnancy than in those who do not have thyroid antibodies; however, whether treatment can prevent post-partum thyroiditis in women who are or have been antibody positive is unknown. Finally, TRAbs cross the placenta from the mother to the fetus and can cause fetal or neonatal hyperthyroidism. Therefore, women who are positive for TRAbs during pregnancy should be monitored.

Is only Thyroid Peroxidase Antibody Sufficient for Diagnosing Chronic Lymphocytic Thyroiditis?

Objectives:

Recently, only anti-thyroid peroxidase (anti-TPO) has been suggested as an autoantibody in the diagnosis of chronic lymphocytic thyroiditis (CLT). In contrast, anti-thyroglobulin (anti-Tg) positivity has also been reported to be important. To evaluate this relationship more clearly, we planned to retrospectively investigate the autoantibody levels of the patients who underwent thyroid surgery for various reasons and those with CLT in postoperative pathology.

Methods:

We evaluated 670 patients who underwent thyroid surgery (total/subtotal thyroidectomy) for various reasons at our hospital between January 2015 and March 2017. Patients with indications of Graves’ disease, toxic multinodular goiter, and all malignancies except for thyroid papillary carcinoma (TPC) were excluded. Eighty-nine patients whose pathology findings were compatible with CLT and preoperative thyroid autoantibodies were identified enrolled in to the study. Patients with absence and presence of thyroid antibodies were included in the seronegative CLT group and seropositive CLT group, respectively. In addition, patients were divided into thyroid papillary carcinoma (TPC) and benign groups.

Results:

According to the study criteria, 89 (83 females, six males) (mean age, 46.08±11.19 years) patients who had preoperatively identified autoantibodies were detected. Anti-TPO positivity was found in 47 (52.8%) cases, whereas anti-Tg positivity was found in 49 (55.1%). Only anti-TPO positivity was found in 18 (20.2%) cases, whereas only anti-Tg positivity was detected in 20 (22.5%). Twenty-two (24.7%) of the patients were seronegative. On comparing the seronegative and seropositive groups, seronegativity was more frequent in male patients (p=0.03). Thyroid-stimulating hormone was found to be significantly higher in the seropositive group (p=0.01). TPC was detected in 36 (40.4%) of all cases. No difference regarding age, thyroid function tests, and antibody levels was found between the benign and TPC groups.

Conclusion:

Although all of our cases were histopathologically diagnosed with CLT, serologically, 75.3% of thyroid autoimmunities could be shown when both antibodies were evaluated together. When only anti-TPO was considered, this rate decreased to 52.8%. Therefore, anti-Tg appears to be still important in showing autoimmunity. Prospective studies are needed to evaluate this relationship more clearly.

The relationship between thyroid antibody titer and levothyroxine dose in patients with overt primary hypothyroidism

BACKGROUND

Both excess and insufficient thyroid hormone replacement may produce adverse effects in various target tissues; therefore, understanding factors that affect achievement of target TSH levels is crucial.

OBJECTIVE

Investigate the relationship between antibody titers and levothyroxine dose.

DESIGN

Retrospective, review of data in medical records.

SETTING

Thyroid center of Fatih Sultan Mehmet Education and Research Hospital, Istanbul, Turkey.

PATIENTS AND METHODS

The study population consisted of patients that had been diagnosed as having overt primary hypothyroidism and were taking levothyroxine for at least one year. The serum TSH level for an euthyroid state was between 0.5-4 mIU/L. The levels of anti-thyroid peroxidase (TPOAb) considered positive for antibodies were < 5.6 IU/mL and for anti-thyroglobulin (TgAb) autoantibodies < 4.10 IU/ mL.

MAIN OUTCOME MEASURE

Daily levothyroxine doses of antibody-positive and negative patients and association of daily drug requirement with antibody titers.

RESULTS

The study population consisted of the 303 patients (273 females and 30 males with the mean [SD] age of 46.6 [13.2] years). In the antibody-positive group (n=210) average daily levothyroxine dose was statistically significantly higher than in the antibody-negative group (n=93) (mean of 78.8 [36.7] vs 64.2 [27.1] mg/day, P=.001, respectively). There was a low but statistically significant positive relationship between the TPOAb (r=0.217, P < .01) and TgAb levels (r=0.158, P < .05) and levothyroxine doses in the antibody-positive group.

CONCLUSION

Antibody titers are positively associated with larger levothyroxine (LT-4) replacement dosing in patients with autoimmune thyroiditis.

LIMITATION

Unknown antibody titers before starting levothyroxine use.

Serum negative autoimmune thyroiditis displays a milder clinical picture compared with classic Hashimoto's thyroiditis

BACKGROUND

Despite high sensitivity of current assays for autoantibodies to thyroperoxidase (TPO) and to thyroglobulin (Tg), some hypothyroid patients still present with negative tests for circulating anti-thyroid Abs. These patients usually referred to as having seronegative autoimmune thyroiditis (seronegative CAT) have not been characterized, and definite proof that their clinical phenotype is similar to that of patients with classic chronic autoimmune thyroiditis (CAT) is lacking.

OBJECTIVE

To compare the clinical phenotype of seronegative CAT (SN-CAT) and CAT as diagnosed according to a raised serum level of TSH with negative and positive tests for anti-thyroid Abs respectively.

METHODS

A case-control retrospective study enrolling 55 patients with SN-CAT and 110 patients with CAT was performed. Serum free triiodothyronine (FT3), free thyroxine (FT4), TSH, Tg Abs, and TPO Abs were measured in all patients.

RESULTS

Patients with SN-CAT displayed significantly lower mean levels of TSH (6.6±3.4 vs 10.2±9.8 μU/ml; P=0.009), higher mean FT4 levels (1.1±0.2 vs 0.9±0.2 ng/dl; P=0.0002), and similar FT3 levels when compared with CAT patients. Mean thyroid volume was significantly greater in patients with CAT when compared with SN-CAT patients (11.2±6.5 vs 8.1±3.7 ml; P=0.001). Logistic regression demonstrated that FT4 (0.123 (0.019-0.775); (P=0.026)) and thyroid volume (1.243 (1.108-1.394); (P=0.0002)) were significantly and independently related to the diagnosis (CAT/SN-CAT). Patients with SN-CAT had a similar prevalence of thyroid nodules and female gender but a lower prevalence of overt hypothyroidism (5.4 vs 20.9%; P=0.012) as opposed to patients with CAT.

CONCLUSIONS

These results suggest an autoimmune etiology of SN-CAT, which, however, seems to have a milder clinical course when compared with CAT.

Risk factors for congenital hypothyroidism in Egypt: results of a population case-control study (2003-2010)

BACKGROUND AND OBJECTIVES

Although the prevention of the neuropsychological consequences of congenital hypothyroidism (CH) through the use of replacement therapy represents an important public health success, knowledge about the modifiable risk factors could reduce the number of infants affected by this disease. This study was carried out to identify risk factors for CH at Fayoum Governorate, Egypt.

DESIGN AND SETTINGS

This was a population-based case-control study, which started in 2003 and was carried out for 8 years through Fayoum center of the Egyptian Ministry of Health and Population screening program for CH.

METHODS

This study was a population-based case-control study carried out by using national project for CH. One control was enrolled for each new CH infant; 320 cases and 320 controls were enrolled in 8 years. Maternal and neonatal influences were investigated.

RESULTS

A statistically significant association of CH was observed with birth defects, female gender, gestational age > 40 weeks, and gestational diabetes. An increased risk for CH was detected in twins by a multivariate analysis.

CONCLUSION

Our results suggest a multifactorial origin of CH in which genetic (high frequency of additional malformations) and environmental factors (especially maternal diabetes) play a role in the development of the disease.

Maternal thyroid dysfunction and neonatal thyroid problems

Aim. To investigate obstetric features of pregnant women with thyroid disorders and thyroid function tests of their newborn infants. Methods. Women with hypothyroidism and having anti-thyroglobulin (ATG) and anti-thyroid peroxidase (anti-TPO) antibodies were assigned as group I, women with hypothyroidism who did not have autoantibodies were assigned as group II, and women without thyroid problems were assigned as group III. Results. Pregnant women with autoimmune hypothyroidism (group I) had more preterm delivery and their babies needed more frequent neonatal intensive care unit (NICU) admission. In group I, one infant was diagnosed with compensated hypothyroidism and one infant had transient hyperthyrotropinemia. Five infants (23.8%) in group II had thyroid-stimulating hormone (TSH) levels >20 mIU/mL. Only two of them had TSH level >7 mIU/L at the 3rd postnatal week, and all had normal free T4 (FT4). Median maternal TSH level of these five infants with TSH >20 mIU/mL was 6.6 mIU/mL. In group III, six infants (6.5%) had TSH levels above >20 mIU/mL at the 1st postnatal week. Conclusion. Infants of mothers with thyroid problems are more likely to have elevated TSH and higher recall rate on neonatal thyroid screening. Women with thyroid disorders and their newborn infants should be followed closely for both obstetrical problems and for thyroid dysfunction.

Thyroid function abnormalities among first-degree relatives of Iranian congenital hypothyroidism neonates

BACKGROUND

Congenital hypothyroidism (CH) is a relatively common metabolic disease in neonates. Until recent years the disorder was usually regarded as occurring in a sporadic manner. Over the past few years, however, a considerable proportion of familial cases have been identified, and possible roles of autoimmune factors suggested. The aim of the present study was to evaluate abnormality of thyroid function tests in first-degree relatives of CH neonates and compared this to the normal population.

METHODS

From 2002 until 2007 thyroid function tests (T4 and thyroid-stimulating hormone [TSH]) were done in randomly selected CH and normal neonates (n= 194 and n= 350, respectively) and their first-degree relatives. Most mothers of the CH neonates and control groups were also evaluated for thyroid peroxidase antibody (TPOAb).

RESULTS

Thyroid function test in first-degree relative of neonates with CH (361 parents, 136 siblings) were compared with those in control groups (665 parents, 478 siblings). Abnormal thyroid function tests were found in 85 patients in the CH group versus 96 patients in the control group; hypothyroidism was found in 75 (15.1%) and 57 subjects (5%) person in the CH and control groups, respectively (P < 0.05). Positive TPO antibody was found in 22 mothers (17.3%) of CH neonates in comparison with 65 mothers (32.5%) of control groups (P < 0.05). Frequency of hyperthyroidism in parents of control group had trend to be higher than parents of CH neonates (P= 0.05)

CONCLUSION

Familial and genetic components play a role in inheritance of CH, but maternal thyroid autoimmunity may not play an important role in the development of CH in Iran.

Abnormalities of maternal thyroid function during pregnancy affect neuropsychological development of their children at 25-30 months

OBJECTIVE

To examine the relationship between specific thyroid abnormalities (subclinical hypothyroidism, hypothyroxinaemia or elevated thyroid peroxidase antibody titres) in women during pregnancy and the subsequent neuropsychological development of their offspring.

DESIGN/PATIENTS

Serum was collected from 1268 women at 16-20 weeks of gestation and thyroid stimulating hormone (TSH), total thyroxine (tT(4)), free thyroxine (fT(4)), and Thyroid peroxidase antibodies (TPOAb) levels were measured. Thyroid function reference ranges specific for pregnancy were used to screen for thyroid abnormalities. Patients with isolated subclinical hypothyroidism (18 cases), hypothyroxinaemia (19 cases), and those who were euthyroid patients with elevated titres of TPOAb (34 cases) were identified. One hundred and forty-two euthyroid and TPOAb-negative women matched for gestational age from the same cohort were selected as controls.

MEASUREMENTS

Intellectual and motor development score evaluations were performed on the children from the pregnancies at 25-30 months of age.

RESULTS

Children of women with subclinical hypothyroidism, hypothyroxinemia and elevated TPOAb titres had mean intelligence scores 8.88, 9.30 and 10.56 points lower than those of the control group (P = 0.008, P = 0.004 and P = 0.001, respectively); mean motor scores were 9.98, 7.57 and 9.03 points lower than those of the controls [P < 0.001, P = 0.007 and P < 0.001, respectively (t-test)]. Unconditional multivariate logistic regression analysis showed that increased maternal serum TSH, decreased maternal serum tT(4), and elevated maternal TPOAb titres were separately associated with lower intelligence scores (ORs 15.63, 12.98, and 6.69, respectively) and poorer motor scores (ORs 9.23, 5.52, and 8.25, respectively).

CONCLUSIONS

Intellectual and motor development of children at 25-30 months of age is separately associated with abnormalities of maternal thyroid at 16-20 weeks gestation. Maternal subclinical hypothyroidism, hypothyroxinaemia or euthyroidism with elevated TPOAb titres were all statistically significant predictors of lower motor and intellectual development at 25-30 months.

Newborn of mothers affected by autoimmune thyroiditis: the importance of thyroid function monitoring in the first months of life

BACKGROUND

Evaluation of thyroid function in neonates born from mothers affected by autoimmune thyroiditis in order to define if a precise follow-up is necessary for these children. The influence of maternal thyroid peroxidase antibody (TPOAb) and L-thyroxine therapy during pregnancy on neonatal thyroid function was also investigated.

METHODS

129 neonates were tested for thyroid function by measurement of free thyroxine (FT4) and thyroid stimulating hormone (TSH) in 3th day, 15th day and at one month of life. TPOAb were measured in all patients; periodical control of thyroid function were performed until 6 months of life if Ab were positive. Data concerning etiology of maternal hypothyroidism and maternal replacement therapy with L-thyroxine during pregnancy were retrospectively collected.

RESULTS

28% neonates showed at least a mild increase of TSH value at the different determinations. In the majority of them, a spontaneous completely normalisation of TSH value was observed within the first month life. L-thyroxine replacement therapy was started in 3 neonates. TPOAb titer and maternal L-thyroxine replacement therapy were not related to alteration of thyroid hormone function in our study population.

CONCLUSIONS

Transient mild elevation of serum TSH above the normal reference value for age is frequently observed in the first month of life in infants born from mothers affected by autoimmune thyroiditis. Persistent hyperthyrotropinemia requiring replacement therapy is observed in 2.2% of these neonates. According to our experience, follow-up is recommended in these newborns; the most accurate and not invasive way to carefully monitor these infants after neonatal screening for CH seems to be serum-testing TSH between 2nd and 4th week of life.

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.

Thyroid blocking antibodies in thyroiditis

Serum from a woman with a history of Hashimoto's thyroiditis, who had given birth to two children with congenital hypothyroidism, contained potent TSH blocking activity. Immunoglobulin preparation from this serum abolished completely TSH-stimulated cAMP production in human thyroid membranes. The blocking activity was associated with the IgG fraction absorbed to and eluted from a Protein A column. The stimulation of adenylate cyclase by a preparation of thyroid-stimulating antibodies from a patient with Graves' disease was also inhibited by the antibodies. In contrast, no effect was observed upon fluoride-stimulated cAMP production. The data indicate that the antibody activity was directed against the TSH receptor. Immunoglobulin preparations from 22 other patients with Hashimoto's thyroiditis and 16 patients with subacute thyroiditis were examined for the existence of TSH receptor blocking antibodies. A blocking activity was found in two of the 22 Hashimoto patients. No such activity was found in the patients with subacute thyroiditis. It appears that thyroid blocking antibodies sometimes contribute to hypothyroidism associated with Hashimoto's thyroiditis.

Thyroid gland development and defects

During the functional ontogenesis of the thyroid gland an increasing number of transcription factors play fundamental roles in thyroid-cell differentiation, maintenance of the differentiated state, and thyroid-cell proliferation. The early growth and development of the fetal thyroid appears to be generally independent of thyroid-stimulating hormone (TSH). TSH and thyroxine (T4) levels increase from the 12th week of gestation until delivery, whereas triiodothyronine (T3) levels remain relatively low. At birth, a cold-stimulated short-lived TSH surge is observed, followed by a TSH decrease until day 3 or 4 of life by T4 feedback inhibition. Disorders of thyroid gland development and/or function are relatively common, affecting approximately one newborn infant in 2000-4000. The most prevalent disease, congenital hypothyroidism, is frequently caused by genetic defects of transcription factors involved in the development of the thyroid or pituitary gland. A major cause of congenital hyperthyroidism is the transplacental passage of stimulating thyrotropin antibodies from the mother to the fetus. Hypothyroxinaemia or hypotriiodthyroninaemia is frequently observed in preterm infants with or without severe non-thyroidal illness. Whereas congenital hypo- and hyperthyroidism may be treated successfully with T4 or thyrostatic drugs, there is still insufficient evidence on whether the use of T4 for treatment of the latter condition results in changes in neonatal morbidity or reductions in neurodevelopmental impairment.

Transient congenital hypothyroidism in an iodine-replete area is not related to parental consanguinity, mode of delivery, goitrogens, iodine exposure, or thyrotropin receptor autoantibodies

OBJECTIVE

To assess transient congenital hypothyroidism (TCH) etiologies in two Iranian cities.

MATERIALS AND METHODS

Cord dried blood spot samples were collected from neonates in Tehran and Damavand. Serum TSH and T4 were measured in those with cord TSH > or =20 mIU/l. Normal serum values at 2-3 weeks of age confirmed transient hyperthyrotropinemia (THT), while persistently abnormal levels revealed congenital hypothyroidism (CH). Normal serum TSH and T4 4-6 weeks after levothyroxine replacement therapy discontinuation at 2-3 yr of age differentiated TCH from persistent CH.

RESULTS

Among 50,409 screened newborns, 9 (1:5601 births) were diagnosed as TCH and compared to 88 full-term neonates (>/=37 weeks' gestation) with THT and 45 normal (cord TSH<20 mIU/l) neonates. At a median age of 11 days, median (range) serum TSH values in TCH, THT, and normal neonates were 36.8 (13-130), 3.6 (0.1-13.3), and 2.9 (0.7-8.0) mIU/l (p<0.0001) and serum T4 values were 97 (36-168), 142 (74-232), and 160 (79-228 nmol/l), respectively (p=0.002). Urinary iodine concentration (UIC) >220 microg/l was observed in 5 (55.6%) of TCH neonates. The occurrence of TCH was not associated with gender, parental consanguinity, mode of delivery, pre- or post-natal consumption of goitrogens and/or thyroid affecting medications, TSH receptor autoantibodies, or neonatal UIC.

CONCLUSIONS

Elevated UIC was the most frequent finding in newborns with TCH but the distribution of excessive UIC was not significantly different among TCH, THT, and normal neonates. Since no other etiologies were found in TCH neonates without elevated UIC values, evaluation of other environmental and/or genetic factors is warranted.

Transient hyperthyroxinemia in newborns from women with autoimmune thyroid disease and raised levels of thyroid peroxidase antibodies

OBJECTIVE

Although it is well established that maternal thyroid disease and increased levels of thyrotropin receptor antibodies (TRab) during pregnancy are associated with a number of complications, is the significance of increased levels of thyroid peroxidase antibodies (TPOab) alone a matter for discussion? The aim of the present study was to examine whether transplacental passage of TPOab from women with autoimmune thyroid disease (AITD) interferes with thyroid function in the neonate.

METHODS

Pregnant women with AITD (raised levels of TPOab) and their neonates were monitored with regard to variations of thyroid hormones, thyrotropin (TSH), and TPOab. Pregnant women with non-AITD served as controls.

RESULTS

The neonates from mothers with AITD, independently of the presence also of TRab in the mothers, had a transient hyperthyroxinemia one week following birth. Neonatal TPOab correlated with that of the mothers at gestation and was cleared concomitantly with normalization of thyroxine. A high frequency (21%) of severe hyperbilirubinemia was observed in neonates from mothers with AITD.

CONCLUSION

Children of mothers with raised levels of TPOab, have a transient hyperthyroxinemia one week after birth accompanied by a high frequency of hyperbilirubinemia suggesting that clinical examination and blood testing should be performed consecutively during the first postnatal week.

Transient neonatal hypothyroidism is associated with elevated serum anti-thyroglobulin antibody levels in newborns and their mothers

Transient congenital hypothyroidism (TCH) was detected in 6 of 35,067 newborns (1:5845 births) screened in Iran. Antithyroglobulin antibodies positivity was present in 4 of 6 (66.7%) of those with TCH and in 6 of 106 (5.7%) of those with "transient hyperthyrotropinemia and normal" diagnoses (P = .0005), but positivity was similar in newborns with transient hyperthyrotropinemia versus normal neonates (P = .397).

Postpartum thyroiditis and autoimmune thyroiditis in women of childbearing age: recent insights and consequences for antenatal and postnatal care

Postpartum thyroiditis is a syndrome of transient or permanent thyroid dysfunction occurring in the first year after delivery and based on an autoimmune inflammation of the thyroid. The prevalence ranges from 5-7%. We discuss the role of antibodies (especially thyroid peroxidase antibodies), complement, activated T cells, and apoptosis in the outbreak of postpartum thyroiditis. Postpartum thyroiditis is conceptualized as an acute phase of autoimmune thyroid destruction in the context of an existing and ongoing process of thyroid autosensitization. From pregnancy an enhanced state of immune tolerance ensues. A rebound reaction to this pregnancy-associated immune suppression after delivery explains the aggravation of autoimmune syndromes in the puerperal period, e.g., the occurrence of clinically overt postpartum thyroiditis. Low thyroid reserve due to autoimmune thyroiditis is increasingly recognized as a serious health problem. 1) Thyroid autoimmunity increases the probability of spontaneous fetal loss. 2) Thyroid failure due to autoimmune thyroiditis-often mild and subclinical-can lead to permanent and significant impairment in neuropsychological performance of the offspring. 3) Evidence is emerging that as women age subclinical hypothyroidism-as a sequel of postpartum thyroiditis-predisposes them to cardiovascular disease. Hence, postpartum thyroiditis is no longer considered a mild and transient disorder. Screening is considered.

The sardinian autoimmunity study. 4. Thyroid and islet cell autoantibodies in sardinian pregnant women at delivery: a cross-sectional study

A high incidence of autoimmune Type 1 diabetes mellitus (DM) has been clearly established in Sardinia. Although systematic epidemiological studies are still not available, an increased prevalence of thyroid autoantibodies (ATA) has been documented in the Sardinian adult population as compared to other Italian regions, suggesting that thyroid autoimmune disease may also have increased. We carried out a preliminary study with the aim of determining the prevalence of serological markers of thyroid (anti-thyroperoxydase antibodies, TPOAb) and islet cell (ICA) autoimmunity in a large number (no.=2249) of sera obtained from cord-blood of Sardinian pregnant women at delivery. The prevalence of TPOAb was 11.9%, while ICA were detected in 59 cases (2.6%). A higher prevalence of TPOAb (6/17=35.3%) was found in sera with high ICA titers (> or = 20 JDF-U), as compared to sera with low ICA titers (5-19 JDF-U) and to ICA-negative sera (3/42=7,1%; chi2=5.4, p=0.02 and 258/2190=11,8%; chi2=6.8, p=0.009 respectively). Fourteen women (all ICA-negative) were diabetic: 4 had Type 1 and 10 had gestational DM; due to the low number, no correlation could be established between DM type and TPOAb prevalence and/or titer. These preliminary data indicate that ATA are frequently observed in the general population of Sardinian pregnant women at term. As a consequence, even the frequency of postpartum thyroiditis is expected to be high. Although ATA were not increased in women with clinical overt diabetes, a higher prevalence of ATA was found in women with high titers of circulating ICA. Our results also confirm that Sardinia represents, perhaps for its peculiar genetic characteristics, an ideal place to study organ-specific autoimmunity.

Relation of basic and clinical research on foetal and neonatal thyroid pathology to neonatal thyroid screening

In this short review the importance is emphasized of basic and clinical research in regard to the interpretation of screening results. This review covers foetal thyroid physiology during the first 48 h of life, the importance of thyroid hormones for normal brain development, the definition of a critical period which might explain intellectual abnormalities in 10-15% of detected hypothyroid children and the importance of autoimmunity in the aetiology and diagnosis of transient congenital hypothyroidism.

Transplacental passage of autoantibodies to triiodothyronine

Autoantibodies to T3 (T3Ab) were detected by immunoprecipitation in a 18-year-old female patient affected by Graves' disease. The presence of these antibodies was constantly confirmed during a 7-year follow-up period, independently of therapy and functional thyroid status. Antithyroid microsomal antibodies (McAb) and TSH binding-inhibiting antibodies (TBII) were also present. The title of AbT3, McAb and TBII fluctuated, at times, independently of one another. The patient became pregnant; during pregnancy T3Ab concentration fell and went up again 4 months after delivery. A normal baby was born. T3Ab were present in the cord blood and declined during the following 2-8 months. The T3Ab of both mother and child belonged to the IgG class. The concentrations and the binding affinities of T3Ab in mother and child were identical. The presence of T3Ab in the child did not affect his thyroid function.

Thyrotrophin-blocking antibodies in congenital hypothyroidism

The role of transplacental transfer of maternal thyrotrophin (TSH)-blocking antibodies causing congenital hypothyroidism in Southern Chinese children was examined in this study. Twenty-two mothers of 24 patients with congenital hypothyroidism were studied 3-5 years after delivery. None of them had thyroid dysfunction at delivery or at the time of study. None had antithyroglobulin or antimicrosomal antibody. Only one mother was found to have TSH-binding inhibitory immunoglobulin (TBII), and her child had agenesis of the thyroid. This women had Graves disease in remission for 2 years before delivery. None had TSH-stimulated cAMP response inhibitory immunoglobulin (TSII). Ten of the 24 congenital hypothyroid children had transient neonatal hypothyroidism, seven had agenesis of the thyroid, six had dyshormonogenesis and one had a sublingual thyroid. As none of the mothers who had children with transient neonatal hypothyroidism had blocking antibodies at the time of study, the aetiology of the transient neonatal hypothyroidism remains unclear. These data suggest that maternal TSH-blocking antibodies do not play a role in most cases of sporadic congenital hypothyroidism.

Congenital hypothyroidism

Because of the lack of signs and symptoms in the first weeks of life, the most important tool for the early diagnosis of congenital hypothyroidism is a newborn screening program.

Circulating thyroid antibodies in congenital hypothyroidism

The role of maternal thyroid antibodies in congenital hypothyroidism is controversial. We have analysed serum thyroid antibodies in patients and their mothers. In a bioassay, antibodies interacting with thyroid cells were analysed by measuring of TSH-stimulated cAMP production in a rat thyroid cell line, FRTL5. Serum antibodies against the TSH receptor, thyroid peroxidase and thyroglobulin were determined by radioreceptor assay and enzyme-linked immunosorbent assays. The bioassay was performed with IgG preparations from 89 mothers of children with congenital hypothyroidism. Analyses for TSH receptor antibodies and thyroid peroxidase/thyroglobulin antibodies were performed on 144 and 118 sera of newborn patients respectively. No evidence of an increased prevalence of thyroid antibodies was found on comparison with controls. One infant had transient neonatal hyperthyrotropinaemia because of TSH receptor blocking antibodies transferred from the mother. Our data indicate that, apart from transplacental transfer of TSH receptor antibodies, maternal immunoglobulins have a limited role in the aetiology of congenital thyroid dysfunction.

Neonatal hypothyroidism: recent developments

This chapter summarizes recent developments in the field of sporadic congenital hypothyroidism (CH) and transient neonatal hypothyroidism detected by systematic neonatal thyroid screening. The incidence of CH detected by screening is about 1 in 4000 births in North America, Europe and Australia; it is lower (1 in 7000) in Japan. The aetiology remains unknown; genetic and environmental factors are possibly involved. The role of autoimmunity has recently been studied extensively. Antithyroglobulin (ATA) and antimicrosomal antibodies are not involved; the possible role of thyroid growth blocking antibodies (TGBAb) of maternal origin remains controversial. Evaluation of clinical signs, bone maturation, serum T4 and the position and size of the thyroid by scintigraphy at the time of diagnosis in CH infants are important because these variables are related to the final psychoneuro-intellectual prognosis, irrespective of the adequacy of therapy. Thyroid echography always distinguishes a normal thyroid in the neonate but cannot define precisely the type of thyroid dysgenesis, if present (e.g. ectopic, athyreosis). The determination of serum Tg contributes to the diagnosis but its specificity and sensitivity are insufficient to replace thyroid scintigraphy. Therapy by LT4, at an initial dose of 25-50 micrograms/day in full-term infants, is universally recommended. The objective of therapy is to reach as soon as possible and to maintain serum concentrations of total and free T4 at the upper limits of normal for age. Serum TSH should decrease as rapidly as possible below 20 microU/ml and then remain within the normal range. Persistent hyperthyrotropinaemia in spite of normal serum T4 has to be avoided as it could represent poor compliance and/or insufficient therapy. Programmes of 10 to 14 years of follow-up of CH infants have now shown that the neuropsychointellectual prognosis of CH is excellent in all cases when therapy and psychosocial environment are adequate. Although still within the normal range, IQ is somewhat lower in spite of appropriate therapy in cases of severe prenatal hypothyroidism and some transient and correctable neurological signs occasionally occur. In Western countries transient neonatal hypothyroidism is usually due to iodine deficiency or iodine excess; the newborn infant is hypersensitive to the antithyroid action of an extraphysiological supply of iodine. TSH binding inhibitor immunoglobulins (TBII) of maternal origin occasionally cause transient neonatal hypothyroidism. In developing countries with severe iodine deficiency and endemic goitre, the incidence of thyroid failure in the newborn can be as high as 1 in 10.(ABSTRACT TRUNCATED AT 400 WORDS)

The value of serum antimicrosomal antibody testing in screening for symptomatic postpartum thyroid dysfunction

We investigated the value of a screening program for postpartum thyroiditis in a heterogeneous American population and used serum antithyroid antibodies to identify postpartum women at risk. Blood was drawn from 1034 consecutive women on their second postpartum day and tested for antimicrosomal and antithyroglobulin antibodies by hemagglutination. Seventy-two women (7.0%) were seropositive for antimicrosomal antibodies, but only seven (0.7%) had antithyroglobulin antibodies. There was a significant difference in the racial prevalence of antimicrosomal antibodies, with seropositivity in 52 of 588 white women (8.8%) versus nine of 367 black women (2.5%; p less than 0.001). Thirty-four of 51 (67%) antimicrosomal seropositive women followed at least 6 months post partum developed biochemical thyroid dysfunction and 20 of these patients required treatment for hypothyroidism. The mean (+/- SEM) serum thyroxine and thyrotropin levels in these patients before treatment were 3.0 +/- 0.3 micrograms/dl (normal 6.1 to 12.3 micrograms/dl) and 77 +/- 17 mU/L (normal 0.3 to 4.0 mU/L), respectively. Psychologic interviews revealed a significant increase in impaired concentration, carelessness, depression, and total complaints when patients with postpartum hypothyroidism were compared with postpartum euthyroid women. Medical evidence now suggests that postpartum thyroiditis is a common event and causes significant symptoms in women who develop hypothyroidism. Therefore, we propose that serum antimicrosomal antibody testing of postpartum women provides a feasible cost-effective screening method of identifying women likely to suffer from this disease.

Autoimmune thyroid disease: an expanding spectrum

Autoimmune thyroid disease classically has included Hashimoto's thyroiditis and Graves' disease. Hashimoto's thyroiditis probably also includes focal thyroiditis, fibrous thyroiditis, primary myxedema, and Hashitoxicosis as variants. Graves' disease is associated with ophthalmopathy and dermopathy, and recent evidence suggests that these manifestations are autoimmune phenomena as well. Other associated autoimmune disorders include idiopathic thrombocytopenic purpura and antigen-antibody complex nephritis. Nonthyroid endocrine autoimmune deficiency disorders also have been classified as part of the spectrum of thyroid autoimmune disease. With the recent recognition of the spectrum of autoimmune mechanisms and antibody types and methods to distinguish antibody functions or types, our understanding of postpartum and neonatal thyroid disorders has been advanced considerably. The spectrum of neonatal thyroid disorders in the infants of women with autoimmune disease relates to the levels and types of antithyroid antibodies acquired from the mother. Finally, there is suggestive evidence that nonspecific goiter, including simple adolescent goiter and multinodular goiter as well as some cases of sporadic cretinism, may be part of an even more expanded spectrum of autoimmune thyroid disease.

Thyrotrophin blocking antibodies in the sera of mothers with congenitally hypothyroid infants

We examined IgG from 15 mothers of infants with congenital hypothyroidism for their ability to block TSH-stimulated iodine organification in vitro. Only one out of 15 of these IgGs exhibited TSH-blocking activity. This IgG could inhibit TSH action by 30-50%. It could not block radiolabelled TSH from binding to its receptor but did inhibit dibutyryl cyclic AMP stimulation of iodine organification implying a unique effect on post-receptor processes via a membrane binding site distant from the TSH binding site. Interestingly there was no evidence of autoimmune thyroid disease in the mother. These results suggest that the transplacental passage of TSH-blocking antibodies plays little, if any, role in the development of congenital hypothyroidism.

Role of maternal immunoglobulins blocking TSH-induced thyroid growth in sporadic forms of congenital hypothyroidism

Among 34 mothers of infants with sporadic congenital hypothyroidism detected in the Quebec screening programme, 15 had immunoglobulins blocking thyroid growth induced by thyroid-stimulating hormone (TSH) when tested in the sensitive Feulgen cytochemical bioassay. At the time of delivery all the mothers were clinically and biochemically euthyroid, and in general the growth-blocking immunoglobulins were found in the absence of thyroid antimicrosomal antibodies. 2 mothers, however, had significant titres of antimicrosomal antibodies. They became hypothyroid 1 and 3 years after delivery. 8 of 16 post-partum infant blood samples were positive for immunoglobulins blocking TSH-induced thyroid growth. 4 of 7 positive mothers tested up to 3 years after delivery had become negative, thus indicating a trend for these immunoglobulins to disappear from the maternal circulation. Thus, transplacental passage of maternal immunoglobulins influencing TSH-induced processes of thyroid growth may play a part in the pathogenesis of sporadic congenital hypothyroidism.

Congenital primary hypothyroidism and HLA

Previous studies have suggested an association between congenital hypothyroidism and HLA-Aw24 or B18 antigens. The frequencies of HLA-A, B and C antigens were studied in 33 unrelated Danish patients with congenital hypothyroidism (5 with aplasia of the thyroid gland, 16 with ectopic thyroids and 8 with thyroid dyshormonogenesis). HLA-Aw24 only appeared in patients with ectopic thyroids and HLA-B18 was only seen in patients with dyshormonogenesis. However, the frequencies of HLA antigens in patients and in a large number of controls did not differ statistically significantly. We conclude that HLA typing is without any predictive value in determining the risk of developing or giving birth to a child with congenital hypothyroidism.

Decrease of thyroid antibodies during pregnancy

The behavior of serum anti-thyroglobulin (Abs-Tg) and antimicrosomal antibodies (Abs-Mc) was examined during and after normal pregnancies. The antibodies titer decreases as pregnancy progresses; they cross the placenta and are present in the fetal serum. Infants' thyroid function is not affected by this transplacentar transfer. The Abs-Tg titer increases again after delivery.