Clinical utility of thyroid ultrasonography in the diagnosis of congenital hypothyroidism

Congenital Hypothyroidism: Screening and Management

ABSTRACT

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

A case of syndromic congenital hypothyroidism with a 15.2 Mb interstitial deletion on 2q12.3q14.2 involving PAX8

Paired box 8 (PAX8) mutations are an established genetic cause of congenital hypothyroidism (CH). The majority of these mutations are found in the protein-coding exons of the gene. The proband, a 3-yr-old girl, had tetralogy of Fallot and polydactyly soon after birth. She was diagnosed with CH in the newborn screening for CH. She had a high serum TSH level (239 mU/L) and low free T4 level (0.7 ng/dL). Ultrasonography revealed thyroid hypoplasia. We performed array comparative genomic hybridization because the patient exhibited a variety of symptoms across multiple organ systems. The analysis revealed a novel heterozygous deletion that spanned a 15.2 Mb region in 2q12.3q14.3 (GRCh37; chr2:109,568,260-124,779,449). There were 71 protein-coding genes in this region, including two genes (PAX8 and GLI2) associated with congenital endocrine disorders. The common clinical features of the two previously reported patients with a total PAX8 deletion and our case were CH, short stature and intellectual disability, but the severity of hypothyroidism and other clinical features were variable. In conclusion, we describe a syndromic CH patient with a novel 2q12.3q14.3 deletion involving PAX8. Patients with CH, whose unifying diagnosis is not obvious, could have a genomic deletion involving PAX8.

Guidelines for Newborn Screening of Congenital Hypothyroidism (2021 Revision)

Purpose of developing the guidelines: Newborn screening (NBS) for congenital hypothyroidism (CH) was started in 1979 in Japan, and early diagnosis and treatment improved the intelligence prognosis of CH patients. The incidence of CH was once about one in 5,000-8,000 births, but has been increased with diagnosis of subclinical CH. The disease requires continuous treatment and specialized medical facilities should conduct differential diagnosis and treatment in patients who are positive by NBS to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, the guidelines were revised in 2014. Here, we have added minor revisions to the 2014 version to include the most recent findings. Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.

Correlation Between Thyroid Hormone Concentrations and Ultrasound Thyroid Volume in Preterm Infants Born Before 33 Weeks of Gestation

OBJECTIVE

Thyroid disorders are commonly concomitant with premature birth; however, indications to start therapy remain unclear due to a lack of gestational age (GA)-specific reference ranges. We aimed to evaluate the age-specific thyroid-stimulating hormone (TSH), free thyroxine (FT4) levels and the correlation between TSH and FT4 serum levels and ultrasound thyroid volume in preterm infants.

MATERIALS AND METHODS

This was an observational, prospective, single-center study of 98 preterm infants born before 33 weeks GA. The infants were divided into the 24-28 weeks and 29-32 weeks GA groups. TSH and FT4 serum levels were measured at two time points: at postnatal age (PNA) 2 weeks and at postmenstrual age (PMA) 32 weeks; the results were compared between groups at two consecutive time points.

RESULTS

There was a statistically significant between-group difference in FT4 concentration. There was a positive correlation between FT4 and GA at both screening times. FT4 in the 24-28 weeks GA group was significantly lower than in the 29-32 weeks GA group. The mean (standard deviation [SD]) FT4 at PNA 2 weeks was 11.72 ± 2.16 pmol/l for the 24-28 weeks GA group vs. 13.33 ± 1.80 pmol/l for the 29-32 weeks GA group (p<0.001). The mean (SD) FT4 at PMA 32 weeks was 11.96 ± 1.98 pmo/l for the 24-28 weeks GA group vs. 13.33 ± 1.80 pmol/l for the 29-32 weeks GA group (p=0.001). Our results reflect a slow and gradual upward trend of FT4 in the 24-28 weeks GA. It is of interest that the correlation between thyroid volume and FT4 was statistically significant (rho=0.25, p=0.019) for all studied preterm infants. The correlation between thyroid volume and weight was statistically significant for the entire study group (rho=0.37, p<0.001). We did not find statistically significant differences in TSH and FT4 values between consecutive time points at 24-28 weeks GA. The thyroid volume was not significantly different between both groups. The total thyroid volume was 0.26 vs. 0.27 ml for the 24-28 and 29-32 weeks GA groups, respectively.

CONCLUSION

The results of this study indicate that preterm infants require lower FT4 values depending on GA. Moreover, ultrasound thyroid imaging may facilitate the evaluation of questionable thyroid disorders.

Dual Oxidase System Genes Defects in Children With Congenital Hypothyroidism

PURPOSE

The objectives of this study were to analyze the distribution of dual oxidase (DUOX) system genes (containing DUOX2, DUOX1, DUOXA2, and DUOXA1) variants in children with congenital hypothyroidism (CH) and their phenotypes.

METHODS

Target region sequencing technology was performed on DUOX system genes among 606 CH subjects covering all the exon and intron regions. Detailed clinical data were collected for statistical analysis.

RESULTS

A total of 95 suspected pathogenic variants were detected in the DUOX system genes, showing a 39.11% rate in variant carrying (237/606). DUOX2 had the highest rate in this study. There were statistical differences in maximum adjusted dose and current dose of levothyroxine between the DUOX system genes nonmutated group with the mutated group (both Ps < 0.001). The cases in the DUOX system genes mutated group were more likely to develop into transient CH (χ 2 = 23.155, P < 0.001) and more likely to manifested as goiter or gland-in-situ (χ 2 = 66.139, P < 0.001). In addition, there was no significant difference in clinical characteristics between DUOX system genes monoallelic and non-monoallelic. Although 20% of the variants affected the functional domain regions (EF hand, flavin adenine dinucleotide and nicotinamide adenine dinucleotide binding sites), there was no significant effect on the phenotype severity whether the variation is located in the functional domain regions.

CONCLUSIONS

Our results showed the high variation rate of DUOX2 in the DUOX system genes among Chinese CH patients. The complex genotype-phenotype relationship of DUOX system genes broadened the understanding of CH phenotype spectrum.

Congenital goitrous hypothyroidism is caused by dysfunction of the iodide transporter SLC26A7

Iodide transport and storage in the thyroid follicles is crucial for thyroid hormone synthesis. Pendrin, the iodide exporter that transports iodide to thyroid follicles, is responsible for Pendred syndrome, a disorder characterized by congenital hypothyroidism and hearing loss. However, thyroid hormone levels are basically normal in patients with Pendred syndrome, indicating the presence of another unknown iodide transporter. Here, we show that SLC26A7 is a novel iodide transporter in the thyroid. We observe that SLC26A7 is specifically expressed in normal thyroid tissues and demonstrate its function in iodide transport. Using whole-exome sequencing, we also find a homozygous nonsense mutation in SLC26A7 (c.1498 C > T; p.Gln500Ter) in two siblings with congenital goitrous hypothyroidism. The mutated SLC26A7 protein shows an abnormal cytoplasmic localisation and lacks the iodide transport function. These results reveal that SLC26A7 functions as a novel iodide transporter in the thyroid and its dysfunction affects thyroid hormonogenesis in humans and causes congenital goitrous hypothyroidism.

Thyroid Imaging in Infants

Congenital hypothyroidism is the most common preventable cause of mental retardation. It is important to know the cause of each patient's thyroid dysfunction to foresee the course of therapy and outcomes. Imaging methods, such as ultrasound and thyroid scan, help determine the anatomy and function of the thyroid gland. Although thyroid scan is considered superior in detecting ectopic thyroid tissue, ultrasound is able to detect the presence of thyroid tissue not otherwise visualized in 15% of patients.

Use of Tc-99 m thyroid scans in borderline congenital hypothyroidism

BACKGROUND

Mild or borderline congenital hypothyroidism [often referred to as mild neonatal hyperthyrotropinemia (MNH)] is characterized by an abnormal newborn screen (NBS), followed by mildly elevated TSH and normal FT4 on confirmatory testing. This condition is increasingly observed, but data regarding optimal management are limited.

OBJECTIVE

Examine the use of routine technetium thyroid scanning (TS) in the management of MNH.

METHODS

Retrospective study of infants with MNH between 2000 and 2011. We assessed the clinical course of infants with MNH according to TS results; as a comparator, infants with classic congenital hypothyroidism (CH) were analysed in parallel.

RESULTS

We identified 69 infants (52% boys) with MNH and 164 (34% boys) with classic CH. TS results were divided into four subgroups: no uptake in 7% of MNH vs 24% of classic CH (P < 0·01), decreased uptake/anatomical abnormalities in 39% vs 46% (p = NS), increased uptake in 35% vs 26% (p = NS) and normal uptake in 19% vs 4% (P < 0·01). In MNH, neither NBS-TSH, confirmatory TSH and FT4, mean LT-4 treatment doses and number of dose escalations, nor post-treatment FT4 and TSH differed among the four subgroups. In contrast, clinical features in infants with classic CH differed among the subgroups. Among MNH infants who reached 3 years of age, trial-off treatment was successful in 6 of 11 (55%) with no apparent difference in success rates among TS subgroups.

CONCLUSIONS

The information provided by TS during evaluation of MNH does not predict clinical course; obtaining these scans in infants with MNH may not be an effective use of healthcare resources.

Sonographic evaluation of children with congenital hypothyroidism

Objective

To establish benchmarks and study some sonographic characteristics of the thyroid gland in a group of euthyroid children aged up to 5 years as compared with age-matched children with congenital hypothyroidism.

Materials and Methods

Thirty-six children (17 female and 19 male) aged between 2 months and 5 years were divided into two groups – 23 euthyroid children and 13 children with congenital hypothyroidism – and were called to undergo ultrasonography.

Results

In the group of euthyroid children (n = 23), mean total volume of the thyroid gland was 1.12 mL (minimum, 0.39 mL; maximum, 2.72 mL); a homogeneous gland was found in 17 children (73.91%) and 6 children (26.08%) had a heterogeneous gland. In the group of children with congenital hypothyroidism (n = 13), mean total volume of the thyroid gland was 2.73 mL (minimum, 0.20 mL; maximum, 11.00 mL). As regards thyroid location, 3 patients (23.07%) had ectopic thyroid, and 10 (69.23%) had topic thyroid, and out of the latter, 5 had a homogeneous gland (50%) and 5, a heterogeneous gland (50%). In the group with congenital hypothyroidism, 6 (46.15%) children had etiological diagnosis of dyshormoniogenesis, 3 (23.07%), of ectopic thyroid, and 4 (30.76%), of thyroid hypoplasia.

Conclusion

Thyroid ultrasonography is a noninvasive imaging method, widely available, easy to perform and for these reasons could, and should, be performed at any time, including at birth, with no preparation or treatment discontinuation, to aid in the early etiological definition of congenital hypothyroidism.

Guidelines for Mass Screening of Congenital Hypothyroidism (2014 revision)

Purpose of developing the guidelines: Mass screening for congenital hypothyroidism started in 1979 in Japan, and the prognosis for intelligence has been improved by early diagnosis and treatment. The incidence was about 1/4000 of the birth population, but it has increased due to diagnosis of subclinical congenital hypothyroidism. The disease requires continuous treatment, and specialized medical facilities should make a differential diagnosis and treat subjects who are positive in mass screening to avoid unnecessary treatment. The Guidelines for Mass Screening of Congenital Hypothyroidism (1998 version) were developed by the Mass Screening Committee of the Japanese Society for Pediatric Endocrinology in 1998. Subsequently, new findings on prognosis and problems in the adult phase have emerged. Based on these new findings, the 1998 guidelines were revised in the current document (hereinafter referred to as the Guidelines). Target disease/conditions: Primary congenital hypothyroidism. Users of the Guidelines: Physician specialists in pediatric endocrinology, pediatric specialists, physicians referring patients to pediatric practitioners, general physicians, laboratory technicians in charge of mass screening, and patients.

The role of scintigraphy and ultrasound in the imaging of neonatal hypothyroidism: 5-year retrospective review of single-centre experience

INTRODUCTION

Congenital hypothyroidism (CH), as indicated by an elevation of capillary thyroid-stimulating hormone (TSH) at newborn screening, is a preventable cause of mental retardation with varying aetiology; it can be transient or permanent. Radionuclide assessment is currently the gold standard for imaging CH. This study aimed to (i) review the different scintigraphic patterns and correlate them with TSH levels/patient outcomes, (ii) assess the role of sonography in neonates with apparent agenesis as indicated by scintigraphy and (iii) develop a diagnostic investigative algorithm.

METHODS

The technetium thyroid scans of 83 consecutive patients (49 females, average age 32 days) with CH scanned between 2005 and 2009 were retrospectively reviewed. Two nuclear medicine physicians blinded to the clinical details interpreted the scans in consensus. Scintigram appearances were categorised into five groups. Patients scintigraphically diagnosed with thyroid agenesis were evaluated with ultrasound. TSH values and scintigraphic and sonographic findings were correlated with patients' final diagnosis.

RESULTS

Based on scintigraphy, 14, 13 and 19 patients out of 83 were assessed as having normal thyroid sites with normal, increased and decreased uptake, respectively. Twenty-two of 83 patients had no uptake, and 15 of 83 patients had ectopic uptake. Higher median TSH levels were seen in no-uptake and ectopic uptake subgroups. Eighteen of 22 patients with no uptake were evaluated with ultrasound. Three of the 18 patients had a normal thyroid gland, and three of 18 patients had a hypoplastic thyroid.

CONCLUSION

Scintigram findings in patients with congenital hypothyroidism fall into five major categories, which have therapeutic implications (lifelong thyroxine in agenesis versus trial of stopping thyroxine in other subgroups). Sonographic demonstration of thyroid tissue in patients scintigraphically diagnosed with thyroid agenesis has major management implications.

Ultrasound for primary imaging of congenital hypothyroidism

OBJECTIVE

The purpose of this study was to retrospectively evaluate the use of sonography as the primary imaging modality for congenital hypothyroidism (CH).

MATERIALS AND METHODS

From our regional registry, we reviewed the cases of patients for whom either sonography or (99m)Tc-pertechnetate scanning was performed for CH between 2003 and 2010. Ultrasound studies were reviewed for presence, size, echotexture, vascularity, and location of the thyroid gland. Technetium-99m-pertechnetate scans were evaluated for the presence and location of the thyroid gland. The ultrasound studies were compared with the (99m)Tc-pertechnetate scans. We assessed the use of ultrasound as the primary imaging modality for the evaluation of CH.

RESULTS

We identified the cases of 124 patients (89 girls, 35 boys). Ultrasound studies were available for 121 patients, and (99m)Tc-pertechnetate studies for 62 patients. Three patients were examined only by (99m)Tc-pertechnetate scanning. The final imaging results were normal location with normal size or diffuse enlargement of the thyroid gland (n = 47), sublingual thyroid gland (n = 49), agenesis (n = 18), hypoplasia (n = 8), and hemiagenesis (n = 2). Compared with (99m)Tc-pertechnetate scanning, ultrasound had high (100%) specificity and low (44%) sensitivity for detection of sublingual thyroid gland.

CONCLUSION

We suggest using ultrasound as the primary imaging modality for guiding the treatment of children with CH, potentially decreasing radiation exposure and cost.

Molecular screening of the TSH receptor (TSHR) and thyroid peroxidase (TPO) genes in Korean patients with nonsyndromic congenital hypothyroidism

OBJECTIVE

To investigate thyroid-stimulating hormone receptor (TSHR) and thyroid peroxidase (TPO) mutations in Korean patients with primary congenital hypothyroidism (CH).

CONTEXT

Congenital hypothyroidism is a common genetic disorder in which the majority of mutations occur in the TSHR and TPO genes.

DESIGN

We examined the frequencies of TSHR and TPO mutations among Korean patients with primary CH. Furthermore, we explored the relationships between imaging findings and mutation status.

PATIENTS

A total of 193 paediatric patients with nonsyndromic CH were enrolled in the present study.

MEASUREMENTS

Patients with decreased (99m) Tc uptake were screened for TSHR mutations using Sanger sequencing, and those with increased uptake were screened for TPO mutations. The relationships between scintigraphic and ultrasonographic findings and mutation status were analysed.

RESULTS

Thirteen (16·5%) of 79 patients with decreased (99m) Tc uptake were found to harbour TSHR mutations including G132R, G245S, R450H, R519C and F525S. The R450H mutation was present in 13 (72·2%) of 18 disease alleles. Seven (10·3%) of 68 patients with increased (99m) Tc uptake harboured TPO mutations including R189Q, K439E, G493S, C808LfsX72, A863T, R875Hfs and P883S. The TSHR and TPO mutations were observed only in patients with normal to slightly enlarged thyroid glands.

CONCLUSIONS

This study identified underlying TSHR and TPO mutations in Korean patients with CH and revealed a possible relationship between imaging findings and mutation status. In addition, the low rate of mutation positivity suggests significant genetic heterogeneity of CH in the Korean population.

Sonographic measurement of thyroid volumes in healthy Chinese infants aged 0 to 12 months

OBJECTIVES

The purposes of this study were to determine thyroid volumes in healthy Chinese infants aged 0 to 12 months and to provide reference data for normal thyroid growth.

METHODS

A total of 408 healthy infants (229 male and 179 female) were enrolled in the study. The length, breadth, and depth of the thyroid gland were measured with sonography. The volume of each lobe was calculated by the correct ellipsoid formula (volume = length × breadth × depth × 0.479).

RESULTS

All of the infants' thyroids showed a normal uniform echo texture on sonography. The thyroid volume increased with age (r = 0.519; P < .001). Moreover, positive associations were noted between thyroid volume and height and weight (r = 0.517; P < . 001; r = 0.499; P < .001, respectively). No significant differences based on sex were found (t = 1.784; P = .075).

CONCLUSIONS

The thyroid volumes in these healthy Chinese infants varied from those reported in the published literature on healthy European infants. It is important to establish local reference ranges for thyroid volumes in healthy infants.

Congenital hypothyroidism: analysis of discordant US and scintigraphic findings

PURPOSE

To retrospectively review discordant cases of congenital hypothyroidism according to a comparison of findings of ultrasonography (US) and scintigraphy.

MATERIALS AND METHODS

Institutional review board approval was obtained for this retrospective study with a waiver of informed consent. Data of 300 pediatric patients (mean age, 4.7 weeks; range, 1-48 weeks; male-to-female ratio, 169:131) with congenital hypothyroidism who underwent technetium 99m radioisotope scintigraphy and US were reviewed. Scintigraphic scans were analyzed for location and range of the radioisotope uptake. US images were analyzed for location and thyroid volume. If a normal thyroid was not detected, ectopic thyroid was evaluated. Detection of focal thyroid abnormalities was recorded. Correlation between radioisotope uptake at scintigraphy and volume of normally located glands measured at US was analyzed by using the Pearson correlation test. Differences between results of thyroid function testing and radiologic data among subtypes of congenital hypothyroidism were analyzed with analysis of variance and Scheffe multiple comparison test.

RESULTS

Among 55 patients with no radioisotope uptake, the appearance of the thyroid gland on US scans was normal in 42 patients (76%). This finding was attributed to hypopituitarism (n = 3), maternal antibody-induced hypothyroidism (n = 4), transient elevated thyrotropin (n = 5), and unknown causes (n = 30). Ectopic tissue was not detected at US (sensitivity, 78%; specificity, 100%) in six patients with a diagnosis of ectopy based on scintigraphic findings. Correlation between radioisotope uptake and US thyroid volume was statistically significant (P < .001). Correlation of results from thyroid function testing (thyrotropin, thyroxine, thyroglobulin) and radiologic data (radioisotope uptake, US measurement of volume) with subtypes of congenital hypothyroidism was significant (P < .001). Solid thyroid nodules were present in the thyroid gland in 0.7% (two of 300) of cases.

CONCLUSION

Use of both scintigraphy and US results in a more complete depiction of neonatal congenital hypothyroidism than either test alone.

Congenital hypothyroidism: etiology

The etiology of congenital hypothyroidism (CH) is important in determining its severity, prognosis, genetic counseling and clinical management.

AIMS

investigate the causes of CH and their severity using serum levels of FreeT4 and TSH.

PATIENTS AND METHODS

243 neonates with CH (61% were girls) diagnosed by the Neonatal Screening Program of Minas Gerais between 1996 and 2003. The thyroid function was assessed through serum FreeT4 and TSH by chemilumiscence. CH etiology was evaluated by ultrasonography, scintigraphy, potassium perchlorate discharge test and serum thyroglobulin levels.

RESULTS

Out of 243 patients, dysgenesis was found in 114 (47%): 3.3% had athyreosis; 0.4% eutopic dysgenetic gland due to maternal use of 131I; 22% ectopic glands (8.6% an isolated ectopic gland and 13% also an eutopic dysgenetic thyroid); 9% eutopic dysgenesis, 8.6% hypoplasia and 3.7% hemiagenesis. Thyroid in situ was found in 129 (52%): 23.5% had iodide organification defect; 3.7% thyroglobulin synthesis defect; 6.2% other 0.4% dyshomonogenesis; iodide transport defect; 1.2% transient CH and 18% a normal gland. Patients with dysgenesis had a more severe CH than those with thyroid in situ (TSH 248.08 vs. 18.17 microIU/mL and FT4 0.32 vs. 0.95 ng/dL, p < 0.001).

CONCLUSIONS

Some cases had more complex dysgenesis, presenting ectopia associated to a dysgenetic eutopic gland. The ultrasound was the best tool to detect the dysgenetic tissue, but the scintigraphy was the most effective in identifying the functioning tissue. The thyroid hormone synthesis defects were found more frequently than expected, but in some cases they could not be defined.

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.

Combined ultrasound and isotope scanning is more informative in the diagnosis of congenital hypothyroidism than single scanning

BACKGROUND

Thyroid imaging is helpful in confirming the diagnosis of congenital hypothyroidism and in establishing the aetiology. Although isotope scanning is the standard method of imaging, ultrasound assessment may be complementary.

AIM

To determine the strengths and weaknesses of thyroid ultrasound and isotope scanning in neonates with thyroid stimulating hormone (TSH) elevation.

METHODS

Babies from the West of Scotland with raised capillary TSH (>15 mU/l) on neonatal screening between January 1999 and 2004 were recruited. Thyroid dimensions were measured using ultrasonography, and volumes were calculated. Isotope scanning was carried out with a pinhole collimator after an intravenous injection of 99m-technetium pertechnetate.

RESULTS

40 infants (29 female) underwent scanning at a median of 17 days (range 12 days to 15 months). The final diagnosis was athyreosis (n = 11), ectopia (n = 12), hypoplasia (n = 8; 3 cases of hemi-agenesis), dyshormonogenesis (n = 5), transient hypothyroidism (n = 2), transient hyperthyrotropinaemia (n = 1) and uncertain status with gland in situ (n = 1). 6 infants had discordant scans with no isotope uptake but visualisation of thyroid tissue on ultrasound. This was attributed to TSH suppression from thyroxine (n = 3); maternal blocking antibodies (n = 1); cystic degeneration of the thyroid (n = 1); and possible TSH receptor defect (n = 1).

CONCLUSIONS

Isotope scanning was superior to ultrasound in the detection of ectopic tissue. However, ultrasound detected tissue that was not visualised on isotope scanning, and showed abnormalities of thyroid volume and morphology. We would therefore advocate dual scanning in newborns with TSH elevation as each modality provides different information.

Update of newborn screening and therapy for congenital hypothyroidism

Unrecognized congenital hypothyroidism leads to mental retardation. Newborn screening and thyroid therapy started within 2 weeks of age can normalize cognitive development. The primary thyroid-stimulating hormone screening has become standard in many parts of the world. However, newborn thyroid screening is not yet universal in some countries. Initial dosage of 10 to 15 microg/kg levothyroxine is recommended. The goals of thyroid hormone therapy should be to maintain frequent evaluations of total thyroxine or free thyroxine in the upper half of the reference range during the first 3 years of life and to normalize the serum thyroid-stimulating hormone concentration to ensure optimal thyroid hormone dosage and compliance. Improvements in screening and therapy have led to improved developmental outcomes in adults with congenital hypothyroidism who are now in their 20s and 30s. Thyroid hormone regimens used today are more aggressive in targeting early correction of thyroid-stimulating hormone than were those used 20 or even 10 years ago. Thus, newborn infants with congenital hypothyroidism today may have an even better intellectual and neurologic prognosis. Efforts are ongoing to establish the optimal therapy that leads to maximum potential for normal development for infants with congenital hypothyroidism. Remaining controversy centers on infants whose abnormality in neonatal thyroid function is transient or mild and on optimal care of very low birth weight or preterm infants. Of note, thyroid-stimulating hormone is not elevated in central hypothyroidism. An algorithm is proposed for diagnosis and management. Physicians must not relinquish their clinical judgment and experience in the face of normal newborn thyroid test results. Hypothyroidism can be acquired after the newborn screening. When clinical symptoms and signs suggest hypothyroidism, regardless of newborn screening results, serum free thyroxine and thyroid-stimulating hormone determinations should be performed.

Diagnostic imaging of the thyroid and adrenal glands in childhood

This article reviews the clinical utility of modern imaging techniques, particularly ultrasound (US), CT, and MRI in children with disorders of the thyroid and adrenal glands. Radionuclide scanning is the modality of choice in making the anatomic diagnosis in neonates with congenital hypothyroidism, while US is most useful in defining nodular thyroid disease. CT and MRI of the thyroid tend to be limited to defining the extent of thyroid carcinoma. Adrenal US is an essential step in the differential diagnosis of ambiguous genitalia or salt-losing crises in the newborn, while CT and MRI are more useful in defining the anatomy of the adrenals in older children with tumors or diffuse hyperplasia of the glands.

Utility of computed tomography in identifying an ectopic thyroid in infants and pre-school children

In purpose of identifying thyroid tissue in patients with congenital hypothyroidism during childhood, ultrasonography is usually used as a screening examination, and scintigraphy is performed secondarily. Though these methods are useful, it is not easy to identify the accurate location of thyroid tissue by these methods. We previously reported the utility of computed tomography (CT) in identifying thyroid tissue in four cases of congenital hypothyroidism. The purpose of this study is to investigate whether CT is useful in identifying thyroid tissue, compared to ultrasonography or scintigraphy. Nineteen cases (0 month to 18 years of age) that were suspected to have ectopic thyroid tissue or thyroid agenesis on ultrasonography were examined by CT. CT was useful in diagnosing ectopic thyroid tissue or thyroid agenesis in all the cases, whereas ultrasonography or scintigraphy was less accurate in this purpose in seven cases. Plain CT had a difficulty in identifying thyroid tissue in two cases, in which contrasted image was required. This study showed that CT, especially an enhanced CT, is useful in identifying thyroid tissue, when the gland is not identified in the normal position by ultrasonography.

Definitive diagnosis in children with congenital hypothyroidism

OBJECTIVES

To investigate the definitive diagnosis and underlying causes of congenital hypothyroidism (CH) in eligible children through the use of a standardized protocol.

STUDY DESIGN

Children > or =3 years of age with CH without an identified permanent cause underwent a diagnostic algorithm. Eligible subjects had an anatomically normal thyroid or had not undergone imaging studies. After thyroxine was discontinued for 4 weeks, thyroid function tests and a thyroid ultrasound were obtained. An abnormal ultrasound was followed by a (99m)Tc thyroid scan. A perchlorate washout test was performed in subjects with a normal ultrasound but abnormal thyroid function tests. Children with normal results were followed for 1 year.

RESULTS

Of 33 children, 17 were boys. Nine (27%) had an absent or ectopic thyroid, 12 (36%) had dyshormonogenesis, and 12 (36%) had transient CH. Average thyroxine dose before medication discontinuation was 2.9 +/- 0.83 microg/kg in permanent cases versus 2.0 +/- 0.53 microg/kg in transient (P <.002). No complications from discontinuation of thyroxine occurred.

CONCLUSIONS

A significant percentage of children with CH have a transient requirement for thyroid hormone. A standardized protocol with thyroid ultrasonography is a safe and sensitive approach to a trial off of thyroxine in select patients.

Color Doppler ultrasonography: diagnosis of ectopic thyroid gland in patients with congenital hypothyroidism caused by thyroid dysgenesis

The etiology of congenital hypothyroidism (CH) may play an important role in determining disease severity, outcome, and, therefore, its treatment schedule. Radionuclide imaging (RI) is currently the most precise diagnostic technique to establish the etiology of CH. Conventional ultrasound can identify an athyrotic condition at the normal neck position and has gained acceptance for the initial evaluation of CH; however, its ability in delineating ectopic thyroid is limited. We used color Doppler ultrasonography (CDU) to assess blood flow and morphology in the detection of ectopic thyroid in 11 CH patients disclosed by neonatal screening; thyroid glands were undetectable at the normal location by gray-scale ultrasonography (GSU). The patients studied consisted of two infants for initial investigation and nine children for reevaluating the cause of CH. All of the patients underwent GSU, CDU, RI, and magnetic resonance imaging (MRI) investigation. We set RI as the defining diagnostic test for detecting ectopic thyroid and compared the imaging of CDU with those of GSU and MRI. The results of RI showed 10 ectopic thyroids and one athyreosis. In the patients with ectopic thyroid, the sensitivity of CDU, GSU, and MRI for detecting ectopic thyroid was 90, 70, and 70%, respectively. We conclude that CDU is superior to GSU and MRI for detecting ectopic thyroid and that CDU may be adopted as the diagnostic tool for the initial investigation of suspected CH.