Frequency of Mutations in the TPO Gene in Patients with Congenital Hypothyroidism Due to Dyshormonogenesis in Chile.

Background and Objectives: Congenital thyroid dyshormonogenesis is caused by alterations in the synthesis of thyroid hormones in a newborn. Additionally, 10 to 20% of these cases are hereditary, caused by defects in proteins involved in hormonal synthesis. One of the most common causes is mutations in the thyroid peroxidase (TPO) enzyme gene, an autosomal recessive disease. We aimed to detect mutations of the TPO gene in 12 Chilean patients with congenital hypothyroidism due to dyshormonogenesis (CHD) and to characterize these patients clinically and molecularly. Materials and Methods: Twelve patients under 20 years of age with CHD, controlled at San Juan de Dios Hospital in Santiago, Chile, were selected according to the inclusion criteria: elevated neonatal TSH, persistent hypothyroidism, and thyroid normotopic by imaging study. Those with deafness, Down syndrome, and central or transient congenital hypothyroidism were excluded. Blood samples were taken for DNA extraction, and the 17 exons and exon-intron junctions of the TPO gene were amplified by PCR. The PCR products were sequenced by Sanger. Results: Two possibly pathogenic mutations of the TPO gene were detected: c.2242G>A (p.Val748Met) and c.1103C>T (p.Pro368Leu). These mutations were detected in 2 of 12 patients (16.6%): 1 was compound heterozygous c.1103C>T/c.2242G>A, and the other was heterozygous for c.2242G>A. In the diagnostic confirmation test, both patients presented diffuse hyper-uptake goiter on thyroid scintigraphy and high TSH in venous blood (>190 uIU/mL). Conclusions: The frequency of patients with possibly pathogenic mutations in TPO with CHD was 16.6%. Its study would allow for genetic counseling to be offered to the families of affected patients.

Infants Diagnosed with Athyreosis on Scintigraphy May Have a Gland Present on Ultrasound and Have Transient Congenital Hypothyroidism.

Scintigraphy using technetium-99m (99mTc) is the gold standard for imaging the thyroid gland in infants with congenital hypothyroidism (CHT) and is the most reliable method of diagnosing an ectopic thyroid gland. One of the limitations of scintigraphy is the possibility that no uptake is detected despite the presence of thyroid tissue, leading to the spurious diagnosis of athyreosis. Thyroid ultrasound is a useful adjunct to detect thyroid tissue in the absence of 99mTc uptake. AIMS: We aimed to describe the incidence of sonographically detectable in situ thyroid glands in infants scintigraphically diagnosed with athyreosis using 99mTc and to describe the clinical characteristics and natural history in these infants. METHODS: The newborn screening records of all infants diagnosed with CHT between 2007 and 2016 were reviewed. Those diagnosed with CHT and athyreosis confirmed on scintigraphy were invited to attend a thyroid ultrasound. RESULTS: Of the 488 infants diagnosed with CHT during the study period, 18/73 (24.6%) infants with absent uptake on scintigraphy had thyroid tissue visualised on ultrasound (3 hypoplastic thyroid glands and 15 eutopic glands). The median serum thyroid-stimulating hormone (TSH) concentration at diagnosis was significantly lower than that in infants with confirmed athyreosis (no gland on ultrasound and no uptake on scintigraphy) (74 vs. 270 mU/L), and median free T4 concentration at diagnosis was higher (11.9 vs. 3.9 pmol/L). Six of 10 (60%) infants with no uptake on scintigraphy but a eutopic gland on ultrasound had transient CHT. CONCLUSION: Absent uptake on scintigraphy in infants with CHT does not rule out a eutopic gland, especially in infants with less elevated TSH concentrations. Clinically, adding thyroid ultrasound to the diagnostic evaluation of infants who have athyreosis on scintigraphy may avoid committing some infants with presumed athyreosis to lifelong levothyroxine treatment.

Permanent vs Transient Congenital Hypothyroidism: Assessment of Predictive Variables.

Objective: To assess clinical variables, including early thyroid scintigraphy, in predicting the outcome (permanent vs transient) in term infants with congenital hypothyroidism (CH). Methods: In a retrospective study, 142 full-term infants with CH diagnosed between 2000 and 2012 were categorized into three groups: agenesis/ectopic thyroid and permanent CH; eutopic thyroid and permanent CH; and eutopic thyroid and transient CH. All underwent early thyroid scintigraphy and were under regular follow-up in our tertiary Pediatric Endocrine Institute. Results: Thyroid scan showed agenesis/ectopic thyroid in 58 (41%) and eutopic thyroid in 84 (59%) infants. Imaging findings were similar in eutopic-permanent and eutopic-transient groups. At initial evaluation, TSH levels were higher in the agenesis/ectopic group than in the eutopic-permanent and eutopic-transient groups (71.5 ± 11.2 mIU/L vs 49.1 ± 27.9 mIU/L and 42.5 ± 29.1 mIU/L, respectively; P < 0.001). Higher l-T4 doses were required from the third month in the agenesis/ectopic than in the eutopic-permanent group (P < 0.001) and from the sixth month in the eutopic-permanent than in the eutopic-transient group (P < 0.01). Initial TSH >63.5 mU/L (P < 0.001) and l-T4 dose >4.6 µg/kg/d at age >6 months (P < 0.001) were found to be predictors for an agenesis/ectopic gland using receiver operating characteristic analysis, as was an l-T4 dose >2.2 µg/kg/d at age >6 months (P < 0.01) for permanent CH in patients with a eutopic gland. Conclusions: Although early thyroid scintigraphy is reliable in predicting permanent CH when detecting agenesis or ectopic gland, it cannot differentiate between permanent and transient CH in cases with a eutopic thyroid. Confirmatory TSH at diagnosis and the l-T4 dose through treatment may better distinguish between permanent and transient CH.

Thyroid ectopy - diagnostic and therapeutic challenges before and in the era of TSH neonatal screening.

Despite TSH screening in newborns is currently conducted in most developed countries, patients with thyroid ectopy born before the procedure was introduced or those in whom the screening failed to establish diagnosis, might still appear. In the paper we revise the current state of knowledge regarding the clinical presentation, diagnosis and treatment of patients with thyroid ectopy. As an example, we report diagnostic and therapeutic difficulties in our three patients with thyroid ectopy remaining undiagnosed and untreated during early childhood. Introduction of neonatal screening for congenital hypothyroidism does not guarantee that all patients with thyroid ectopy will be correctly diagnosed and properly treated due to the possibility of falsely negative result of TSH screening or lack of compliance from parents. Visualization of an ectopic thyroid on ultrasound examination may be challenging for unexperienced sonographists; muscles in the thyroid bed may be misdiagnosed as heterogeneous and hypoechogenic thyroid gland with features suggesting autoimmune thyroid disease. Thyroid scintiscan is crucial for confirmation of the diagnosis of thyroid ectopy. In conclusion, hypothyroidism due to thyroid developmental anomaly should be taken into consideration in case of hypothyroidism and normal thyroid autoantibodies in a patient at any age.

Seasonal variations in TSH serum levels in athyreotic patients under L-thyroxine replacement monotherapy.

BACKGROUND: Whether serum TSH undergoes seasonal fluctuations in euthyroid and hypothyroid residents of temperate climates is controversial. METHODS: Monthly TSH and thyroid hormone levels were cross-sectionally analysed in a large cohort of euthyroid subjects (n=11 806) and L-thyroxine (L-T4)-treated athyreotic patients (n=3 934). Moreover, in a small group (n=119) of athyreotic patients treated with an unchanged dosage of L-T4 monotherapy, hormones were measured both in the coldest and in the hottest seasons of the same year (longitudinal study). RESULTS: No seasonal hormone change was observed in the euthyroid subjects except for a small FT3 increase in winter (+2.9%, P<.001). In contrast, the L-T4-treated athyreotic patients had significantly higher serum TSH values in the cold season when the FT4 values were significantly lower. The differences were more notable in the longitudinal series (TSH, 0.80 vs. 0.20 mU/L and FT4, 16.3 vs. 17.8 pmol/L in December-March vs. June-September, respectively). In these patients also serum FT3 values significantly decreased in winter (in the longitudinal series, 3.80 in winter vs 4.07 pmol/L in summer). Regression analysis showed that in athyreotic subjects, a greater FT4 change is required to obtain a TSH change similar to that of euthyroid controls and that this effect is more pronounced in the summer. CONCLUSION: Athyreotic patients undergoing L-T4 monotherapy have abnormal seasonal variations in TSH. These changes are secondary to the FT4 and FT3 serum decreases in winter, which occur in spite of the constant treatment. The underlying mechanisms are unclear, but in some cases, these changes may be clinically relevant.

Thyroid dysfunction and developmental anomalies in first degree relatives of children with thyroid dysgenesis.

BACKGROUND: Familial clustering in patients with permanent congenital hypothyroidism (CH) caused by thyroid dysgenesis (TD) has been reported in developed countries. There is no information on familial TD from developing countries. METHODS: A total of 312 first degree relatives belonging to 80 families of children with TD (group 1) and 40 families of age-matched normal children (group 2) were screened by thyroid ultrasonography, serum total thyroxine (T4) and thyroid stimulating hormone (TSH). RESULTS: Thyroid scintigraphy revealed agenesis in 78.7% of the patients, ectopic gland in 15%, and hypoplasia in 6.2%. The mean thyroid volumes were similar in parents and siblings of both groups. Eight (10.6%) mothers in group 1 were identified to have thyroid hypoplasia as compared with none in group 2 (P=0.03). Serum TSH was significantly higher in group 1 than in group 2 (P=0.004). Sixteen (7.8%) subjects (6 mothers, 5 fathers, and 5 siblings) in group 1 were found to have subclinical hypothyroidism as compared to none in group 2 (P<0.05). Four families were identified to have thyroid developmental anomalies and abnormal thyroid functions accounting for 5% of cases of familial TD in our cohort. CONCLUSION: Thyroid developmental anomalies and thyroid function abnormalities are more frequent in first degree relatives of children with TD as compared with a control population. These findings suggest that possibly there is a genetic component of TD in Indian patients.

The role of ¹²³I imaging in the evaluation of infants with mild congenital hypothyroidism.

BACKGROUND/AIMS: Controversy exists regarding the diagnosis and treatment of mild congenital hypothyroidism (MCH). We studied the value of (123)I imaging in patients with MCH. METHODS: Retrospective chart review of infants and children <4 years of age who underwent (123)I imaging: group 1 = MCH [thyroid-stimulating hormone (TSH) <25 µIU/ml, normal free T4/T3], group 2 = severe congenital hypothyroidism (TSH ≥25 µIU/ml), and group 3 = MCH in infancy imaged after treatment withdrawal at age 3 years. Data collected included 4- and 24-hour (123)I uptake, TSH, free T4/total T3 at imaging, age at imaging, and levothyroxine (L-T4) dose at 1 year of. RESULTS: Thirty-six patients underwent (123)I imaging. In group 1 (n = 20, median TSH: 8.49 µIU/ml), 85% had abnormal imaging consistent with dyshormonogenesis. Two patients were referred after 1 year of age. The median age at imaging for the remaining 18 patients was 54 days. Median L-T4 dose at 1 year of age for these 18 patients was 2.8 µg/kg, which is consistent with dyshormonogenesis. Ninety-one percent of group 2 (n = 11, median TSH: 428.03 µIU/ml) had abnormal imaging. The median age at imaging was 13 days. Four patients in group 3 had abnormal (123)I imaging and restarted treatment. CONCLUSION: (123)I imaging is a valuable tool for evaluation, diagnosis, and treatment of MCH.

The different requirement of L-T4 therapy in congenital athyreosis compared with adult-acquired hypothyroidism suggests a persisting thyroid hormone resistance at the hypothalamic-pituitary level.

BACKGROUND: Levothyroxine (l-T4) is commonly employed to correct hormone deficiency in children with congenital hypothyroidism (CH) and in adult patients with iatrogenic hypothyroidism. OBJECTIVE: To compare the daily weight-based dosage of the replacement therapy with l-T4 in athyreotic adult patients affected by CH and adult patients with thyroid nodular or cancer diseases treated by total thyroidectomy. DESIGN AND METHODS: A total of 36 adult patients (27 females and nine males) aged 18-29 years were studied; 13 patients (age: 21.5±2.1, group CH) had athyreotic CH treated with l-T4 since the first days of life. The remaining 23 patients (age: 24±2.7, group AH) had hypothyroidism after total thyroidectomy (14 patients previously affected by nodular disease and nine by thyroid carcinoma with clinical and biochemical remission). Patient weight, serum free thyroid hormones, TSH, thyroglobulin (Tg), anti-Tg, and anti-thyroperoxidase antibodies were measured. Required l-T4 dosage was evaluated. At the time of the observations, all patients presented free thyroid hormones within the normal range and TSH between 0.8 and 2 µIU/ml. RESULTS: Patients had undetectable Tg and anti-thyroid antibodies. The daily weight-based dosage of the replacement therapy with l-T4 to reach euthyroidism in patients of group CH was significantly higher than that in those of group AH (2.16±0.36 vs 1.73±0.24 µg/kg, P<0.005). Patients of group CH treated with l-T4 had significantly higher serum TSH levels than patients of group AH (P=0.05) as well as higher FT4 concentrations. CONCLUSIONS: To correct hypothyroidism, patients of group CH required a daily l-T4 dose/kg higher than group AH patients, despite higher levels of TSH. The different requirement of replacement therapy between adult patients with congenital and those with surgical athyroidism could be explained by a lack of thyroid hormones since fetal life in CH, which could determine a different set point of the hypothalamus-pituitary-thyroid axis.

Clinical genetics of congenital hypothyroidism.

Congenital hypothyroidism (CH) is a state of insufficient thyroid hormone supply to the organism, starting in utero. Two forms of permanent primary or thyroidal CH are known. Thyroid dysgenesis (TD) describes a spectrum of defects of thyroid organogenesis. Five monogenetic forms due to mutations in TSHR, PAX8, NKX2-1, FOXE1 and NKX2-5 have been identified so far. Thyroid dyshormonogenesis comprises defects at every step of thyroid hormone synthesis. Mutations in 7 genes are well described causing iodine transport defect (SLC5A5), iodine organification defect (TPO, DUOX2, DUOXA2, SLC26A4), thyroglobulin (TG) synthesis or transport defect or iodotyrosine deiodinase (IYD/DEHAL1) deficiency. The new consensus guidelines for CH recommend genetic counseling for each family with an affected child. Mode of inheritance, recurrence rate and possible associated malformations in the context of syndromic forms should be outlined. Molecular genetic studies should be preceded by a detailed phenotypic description of the patient's thyroid disease and a detailed family history. This review summarizes clinical, biochemical and radiological phenotypes and molecular aspects of the known genetic forms of TD and thyroid dyshormonogenesis relevant for genetic counseling and molecular studies.

Unexpected conversion from hypothyroidism to an euthyroid state due to Graves' disease in a patient with an ectopic thyroid.

A 15-year-old woman was diagnosed with hypothyroidism and unilateral ectopic thyroid. Levothyroxine treatment was introduced; however, the patient was non-compliant and took the medication irregularly. When she presented to an endocrinologist at the age of 30, she had not been using levothyroxine for at least 6 months. Surprisingly, she was clinically and biochemically euthyroid. Due to decreased echogenicity on ultrasound examination, enhanced vascularization on Color Doppler examination and increased concentration of anti-TSH receptor autoantibodies, she was diagnosed with Graves' disease. Eventually, she underwent total thyroidectomy due to diagnosis of follicular neoplasm in fine-needle aspiration biopsy of the focal lesion found in the thyroid gland. To our knowledge, our patient is the first described with ectopic thyroid, presenting a nodular variant of Graves' disease and no signs of orbitopathy, who was initially hypothyroid and became euthyroid in the course of autoimmune thyroid disease.

Novel heterozygous thyrotropin receptor mutation presenting with neonatal hyperthyrotropinaemia, mild thyroid hypoplasia and absent uptake on radioisotope scan.

Hyperthyrotropinaemia [mildly elevated thyrotropin (TSH) with normal thyroxine (T4) levels] demands a full assessment, including clinical examination, thyroid imaging and, where indicated, molecular genetic investigations. A male infant, both of whose parents were on T4 treatment, was referred at age 57 days with mild but persistent TSH elevation (12.7 mU/L) and normal free T4 (19.6 pmol/L), following notification by the screening laboratory of a capillary TSH of 10.7 mU/L (reference range, 1.7-9.1 mU/L) on day 8. Assessment showed a venous free T4 level of 15 pmol/L, venous TSH of 20.9 mU/L, serum thyroglobulin of 63 µg/L (reference range, <50 µg/L), and negative thyroglobulin and thyroid peroxidase antibodies. Thyroid ultrasound showed a eutopic, slightly small gland with heterogeneous texture; however, there was no uptake on radioisotope scan. Molecular genetic studies demonstrated a novel missense heterozygous mutation in the TSH receptor (TSHR) gene (c.1169G>T;p.Cys390Phe) in the child, mother and maternal grandmother, but not in the father. The infant was treated with T4 but this was discontinued at age 3 years when repeat testing showed a free T4 of 16.7 pmol/L (reference range, 9-23 pmol/L) and TSH of 8.5 mU/L (reference range, 0.3-5.5 mU/L). A heterozygous TSHR mutation should be considered in the context of hyperthyrotropinaemia and reduced/absent uptake on radioisotope scan. Detection of this mutation has allowed our patient to discontinue T4 treatment for the moment, with a view to staying off treatment in the long-term.

Congenital hypothyroidism due to defects of thyroid development and mild increase of TSH at screening: data from the Italian National Registry of infants with congenital hypothyroidism.

CONTEXT: Over the years lower TSH cutoffs have been adopted in some screening programs for congenital hypothyroidism (CH) worldwide. This has resulted in a progressive increase in detecting additional mild forms of the disease, essentially with normally located and shaped thyroid. However, the question of whether such additional mild CH cases can benefit from detection by newborn screening and early thyroid hormone treatment is still open. OBJECTIVE: The aim of this study was to estimate the frequency of cases with mild increase of TSH at screening in the Italian population of babies with permanent CH and to characterize these babies in terms of diagnosis classification and neonatal features. METHODS: Data recorded in the Italian National Registry of infants with CH were analyzed. RESULTS: Between 2000 and 2006, 17 of the 25 Italian screening centers adopted a TSH cutoff at screening of <15.0 µU/mL. It was found that 21.6% of babies with permanent CH had TSH at screening of 15.0 µU/mL or less, whereas this percentage was 54% in infants with transient hypothyroidism. Among the babies with permanent CH and mild increase of TSH at screening (≤15 µU/mL), 19.6% had thyroid dysgenesis with serum TSH levels at confirmation of the diagnosis ranging from 9.9 to 708 µU/mL. These babies would have been missed at screening if the cutoff had been higher. CONCLUSIONS: Lowering TSH cutoff in our country has enabled us to detect additional cases of permanent CH, a number of which had defects of thyroid development and severe hypothyroidism at confirmation of the diagnosis.

A strategy to avoid missed cases in a Brazilian neonatal TSH screening program for congenital hypothyroidism.

BACKGROUND: There have been reports of patients with primary hypothyroidism not identified by TSH measurement due to a presumably delayed rise in serum TSH. However, there are no data on the incidence of false negative results in neonatal screening programs employing primary TSH assay for diagnosis. AIM: To investigate the incidence of false negative results in a neonatal screening program using the primary TSH approach and evaluate a strategy to avoid misdiagnosis. INFANTS AND METHODS: 190 newborns, with initial TSH > 15.0 IU/l and < 20.0 IU/l (screening cutoff). These infants were submitted to a second TSH measurement around 30 days after the first screening. RESULTS: Thirty days after the first screening, four of the 190 infants (2.1%) remained with TSH levels around the cut-off screening level or higher. Of these four patients, three had an absence of thyroid gland on ultrasonography, with a final diagnosis of dysgenesis. The fourth patient had a normal shaped gland in its usual location by ultrasonography, with an outcome of transitory congenital hypothyroidism. CONCLUSIONS: The incidence of missed congenital hypothyroidism diagnoses in this neonatal screening program based on the TSH approach was low and acceptable. Nevertheless, with the proposed strategy, the risk of false negative results can be reduced without significant impact on the overall cost of the screening program.

Children with congenital hypothyroidism: long-term intellectual outcome after early high-dose treatment.

We aim to determine long-term intellectual outcome of adolescents with early high-dose treated congenital hypothyroidism (CH). Sixty-three prospectively followed children with CH were assessed at age of 14 y with the Wechsler Intelligence Scale for Children-Revised and compared with 175 healthy controls. Median age at onset of treatment was 9 d (range 5-18 d) and median starting dose of levothyroxine (L-T4) was 14.7 microg/kg/d (range 9.9-23.6 microg/kg/d). Full-scale intelligence quotient (IQ) was significantly lower than in controls after adjustment for socioeconomic status (SES) and gender (101.7 versus 111.4; p < 0.0001). Children with athyreosis had a lower performance IQ than those with dysgenesis (adjusted difference 7.6 IQ scores, p < 0.05). Lower initial thyroxine (T4) levels correlated with poorer IQ (r = 0.27, p = 0.04). Lower SES was associated with poorer IQ, in particular in children with CH (interaction, p = 0.03). Treatment during childhood was not related to IQ at age 14 y. Adolescents with CH manifest IQ deficits when compared with their peers despite early high-dose treatment and optimal substitution therapy throughout childhood. Those adolescents with athyreosis and lower SES are at particular risk for adverse outcome. Therefore, early detection of intellectual deficits is mandatory in children with CH.

Prevalence of thyroid hemiagenesis in an asymptomatic schoolchildren population.

BACKGROUND: Thyroid hemiagenesis is a rare congenital anomaly in which one lobe of thyroid gland fails to develop. Because variations of the prevalence of this anomaly have been reported, the aim of this study was to evaluate the prevalence rate of thyroid hemiagenesis in an apparently normal population from Northern Poland. METHODS: Ultrasound examination of the thyroid gland was performed in 4004 unselected 7-15-year-old school-children from the seaside zone of Northern Poland. RESULTS: Two cases of thyroid hemiagenesis were found, both being absence of the left lobe in two girls. Thyroid volumes, adjusted to body surface area, were within normal range; serum thyrotropin, free thyroxine, and free triiodothyronine were within normal limits. Physical examination, abdominal ultrasound, and echocardiography did not show extrathyroidal malformations. Thyroid ultrasound was normal in the girls, parents, and siblings. CONCLUSIONS: The study showed a 0.05% prevalence of thyroid hemiagenesis in asymptomatic schoolchildren population from iodine-sufficient area of Northern Poland.

High prevalence of thyroid peroxidase gene mutations in patients with thyroid dyshormonogenesis.

OBJECTIVE: Thyroid dyshormonogenesis is a genetically heterogeneous group of inherited disorders in the enzymatic cascade of thyroid hormone synthesis that result in congenital hypothyroidism (CH). Thyroid peroxidase gene (TPO) mutations are one of the most common causes of thyroid dyshormonogenesis. The aim of this study was to identify TPO gene defects in a cohort of patients with thyroid dyshormonogenesis from Slovenia, Bosnia, and Slovakia. DESIGN AND METHODS: Forty-three patients with permanent CH and orthoptic thyroid glands from 39 unrelated families participated in the study. Mutational analysis of the TPO gene and part of its promoter consisted of single-stranded conformation polymorphism analysis, sequencing, and restriction fragment length polymorphism (RFLP) analysis. RESULTS: TPO gene mutations were identified in 46% of participants. Seven different mutations were identified, four mutations of these being novel, namely 613C > T (R175X), 1519_1539del (A477_N483del), 2089G > A (G667S), and 2669G > A (G860R). Only a single allele mutation was identified in 65% of the TPO mutation carriers. CONCLUSIONS: The results showed a higher prevalence of TPO gene mutations in thyroid dyshormonogenesis when compared with published studies. The high percentage of single allele mutations implied possible intronic or regulatory TPO gene mutations or monoallelic expression.