Neonatal hypothyroidism: comparison of radioisotope and ultrasound imaging in 54 cases

Thyroid imaging study in children with suspected thyroid dysgenesis

PURPOSE

Thyroid dysgenesis is one of the most common causes of permanent congenital hypothyroidism. Thyroid ultrasonography or scan is used to detect thyroid dysgenesis. We analyzed the sensitivity and specificity of thyroid ultrasonography and scan in diagnosing thyroid dysgenesis to determine the clinical utility of each thyroid imaging method.

METHODS

Sixty-one patients younger than 7 years of age were investigated via thyroid scan. Nineteen patients who were initially interpreted as having thyroid dysgenesis, such as ectopia, hemiagenesis, or aplasia, by thyroid scan were included in the study. Clinical characteristics and findings of a thyroid imaging study were reviewed.

RESULTS

Initially, thyroid scan results were interpreted as ectopia (n=9), hemiagenesis (n=1), and nonvisualization (n=9). In contrast, the results of thyroid ultrasonography were normal thyroid gland (n=5), ectopia (n=6), and hypoplasia (n=8). After reviewing the results of both studies, final imaging diagnoses were as follows: normal thyroid gland (n=5), hemiagenesis (n=1), ectopia (n=9) including 2 dual ectopy, hypoplasia (n=3), and aplasia (n=1). Thyroid ultrasonography showed higher sensitivity and specificity in detecting presence of normal thyroid gland. Thyroid scan was better to detect ectopia. Among 8 patients who were initially interpreted as having hypoplasia by ultrasonography, 4 were confirmed as ectopia and one as aplasia.

CONCLUSION

This study showed that thyroid ultrasonography is useful as the first-line imaging study to detect normal-sized eutopic thyroid gland. Thyroid scan should be performed to investigate the presence of ectopia if hypoplasia or aplasia is suspected by ultrasonography.

Timing of thyroid ultrasonography in the etiological investigation of congenital hypothyroidism

OBJECTIVES

To describe the findings of thyroid ultrasonography (T-US), its contribution to diagnose congenital hypothyroidism (CH) and the best time to perform it.

SUBJECTS AND METHODS

Forty-four patients with CH were invited to undergo T-US and 41 accepted. Age ranged from 2 months to 45 years; 23 patients were females. All were treated with L-thyroxine; 16 had previously undergone scintigraphy and 30 had previous T-US, which were compared to current ones.

RESULTS

At the current T-US, the thyroid gland was not visualized in its normal topography in 10 patients (24.5%); 31 T-US showed topic thyroid, 17 with normal or increased volume due to probable dyshormonogenesis, 13 cases of hypoplasia and one case of left-lobe hemiagenesis. One patient had decreased volume due to central hypothyroidism. Scintigraphy scans performed 3-4 years earlier showed 100% agreement with current results. Comparisons with previous T-US showed concordant results regarding thyroid location, but a decrease in current volume was observed in eight due to the use of L-thyroxine, calling the diagnosis of hypoplasia into question.

CONCLUSIONS

The role of T-US goes beyond complementing scintigraphy results. It allows inferring the etiology of CH, but it must be performed in the first months of life. An accurate diagnosis of CH will be attained with molecular study and the T-US can guide this early assessment, without therapy withdrawal.

Dual thyroid ectopia-role of thyroid scintigraphy and neck ultrasonography

Ectopic thyroid tissue (ETT) is a rare developmental anomaly of the thyroid tissue where the thyroid gland is not located in its usual position. Dual thyroid ectopia is far rarer. This case of a 5-year-old euthyroid girl with thyroglossal cyst was planned for surgery. Presurgical ultrasonography (USG) of the neck followed by thyroid scintigraphy was performed. There was absent normal thyroid gland with single ETT in neck swelling on USG. However, thyroid scintigraphy revealed two ectopic foci of thyroid tissue; one was corresponding to neck swelling, and other was superior to it at the base of the tongue along with absent eutopic thyroid gland. The repeat neck USG could demonstrate the same. The present case emphasizes that, if the thyroid gland is not visible by USG; ETT should be evaluated with thyroid scintigraphy in case of thyroid dysgenesis.

Imaging the thyroid in children

Color Doppler Ultrasounds (CDU) and Thyroid Scanning (TS) have much improved in recent years and offer a likely diagnosis of the disorder and its main subtypes. This especially applies when diagnosing permanent or transient causes of congenital hypothyroidism (CH), where dual imaging has proven to be more informative than single scanning. Though both isotopes have acceptable performances, the use of (123)I appears more advisable, since it more accurately identifies the various aetiologies of CH and probably has better dosimetric characteristics than (99m)Tc. Detailed dual imaging patterns are presented in connection with most of the underlying mechanisms explaining CH, thyroid dysgenesis (75%) and dyshormonogenesis (20%). Imaging of thyroid autoimmunity, of immunogenic thyrotoxicosis and of thyroid autonomy, is helped by CDU but most often requires a quantified (123)I-TS (molecular imaging). We finally show the interest of CDU to sort suspicious nodule and present the new TIRADS scoring system.

Pitfalls in the diagnosis of thyroid dysgenesis by thyroid ultrasonography and scintigraphy

OBJECTIVES

We aimed to investigate the reliability of thyroid ultrasonography (US) and scintigraphy in determining the type of thyroid dysgenesis (TD).

METHODS

The study included 82 children (8.0±5.6 years) with a diagnosis of TD by thyroid scintigraphy with (99m)Tc and/or US. The patients were re-evaluated 6.0±5.1 years after the diagnosis. Thyroid US was performed in all cases, regardless of the previous US imaging. Scintigraphy images performed at the time of diagnoses (n=60) were re-evaluated during the study. Those who had no scintigraphy at the time of diagnosis (n=22) or had discordant findings with US (n=6) underwent a new scintigraphy.

RESULTS

Scintigraphies revealed no uptake in 37, ectopia in 35, and hypoplasia in 10 cases. The sensitivity vs specificity for US to detect athyreosis, ectopia, and hypoplasia at the time of initial diagnoses was 90.5 vs 47.8, 10 vs 100, and 100 vs 80.4% respectively. The sensitivity vs specificity for scintigraphy at the time of initial diagnoses was 96.2 vs 100, 92 vs 97.1, and 100 vs 96%, respectively, for each diagnosis. Re-scintigraphy at the time of the study led to a change in the initial diagnosis of 3/6 cases. Repeated US showed disappearance of previously reported hypoplastic thyroid tissues in eight patients.

CONCLUSION

US alone could not differentiate ectopia and athyreosis, whereas scintigraphy alone is also prone to mistakes in newborns and young ages. Dual thyroid imaging is important for precise structural definition of TD.

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.

Heterogeneous tissue in the thyroid fossa on ultrasound in infants with proven thyroid ectopia on isotope scan--a diagnostic trap

BACKGROUND

Thyroid imaging is of proven help in establishing a diagnosis of congenital hypothyroidism in infants. US often shows tissue in the thyroid fossa when radionuclide scintigraphy reveals only ectopic uptake.

OBJECTIVE

Our hypothesis was that the use of US alone could lead to the mistaken diagnosis of normal or dysplastic thyroid in cases of scintigraphy-proven thyroid ectopia.

MATERIALS AND METHODS

We undertook a detailed retrospective review and analysis of imaging and concurrent biochemistry in infants with thyroid ectopia, confirmed by radionuclide scintigraphy.

RESULTS

Eighteen infants had thyroid ectopia; ten of the original US reports had suggested that cervical thyroid tissue was present. Review showed bilateral tissue in the thyroid fossa in all that was non-thyroidal in nature since, apart from showing no radionuclide uptake, it exhibited some or all of the following typical features: hyperechogenicity, heterogeneity, small size, poor vascularity, and anechoic and/or hypoechoic cysts. Also, extension of the tissue both around and behind the large cervical blood vessels was a universal finding.

CONCLUSION

Considerable experience is required to interpret neonatal thyroid US. We caution against diagnosing a dysplastic/hypoplastic thyroid gland in situ on the basis of US alone, particularly if the tissue exhibits any of the non-thyroidal features described.

Longitudinal Assessment of Levo-Thyroxine Therapy for Congenital Hypothyroidism: Relationship with Aetiology, Bone Maturation and Biochemical Features

AIMS

To evaluate therapy and dose adjustments in patients with congenital hypothyroidism (CH), longitudinally followed up until 16 years old, according to aetiology, Beclard's nuclei presence, and thyroxine (T4) level at diagnosis.

METHODS

L-T4/kg/day and dose change ratio (CR) were assessed in 74 CH patients.

RESULTS

The dose was statistically larger in athyreosis than in dyshormonogenesis (1-10 and beyond 14 years) and in ectopy (2, 15, 16 years). The ectopic children required statistically larger L-T4/kg than the dyshormonogenetic ones (3-7 years). The L-T4/kg/day was increased, not statistically, in patients or with T4 <30 nmol/l or without Beclard's nuclei at diagnosis. The CR progressively dropped after the 6th month at each attendance, without any difference in terms of aetiology, T4 level at diagnosis, or Beclard's nuclei. The total CR was greater (significantly) in patients without Beclard's nuclei, and (not significantly) in those with T4 <30 nmol/l at diagnosis or with agenesia.

CONCLUSION

The L-T4 dose in CH is highly affected by the aetiology. The CR is higher in patients with delayed bone maturation at diagnosis. We suggest that these latter patients need blood tests more frequently to obtain a proper titration of the therapy.

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.

Thyroid abnormalities by ultrasonography in neonates with congenital hypothyroidism

OBJECTIVES

To investigate the usefulness of thyroid ultrasonography for neonates with congenital hypothyroidism. Study design Patients (n=66) were evaluated by ultrasonography at age 15.2+/-12 days.

RESULTS

Thyroid scanning was more sensitive for the identification of ectopic tissue as ultrasonography showed ectopic thyroid tissue in only 9 of 42 cases. In cases for which no iodine uptake was demonstrated by thyroid scanning (n=12), ultrasonography showed normally located thyroid tissue in 2 patients. Therefore, on the basis of both thyroid scanning and ultrasonography, 10 cases were classified as athyreosis, and 14 cases were classified as showing normal location of the thyroid gland. Among the latter 14 cases, 5 showed a developmental abnormality. Ultrasonography also revealed additional phenotypic abnormalities in patients with thyroid dysgenesis, with cysts (n=6) and thymus tissue (n=4) within the empty thyroid area, which are novel observations in these patients.

CONCLUSIONS

Ultrasonography may reveal additional findings with regard to those obtained by scintigraphy such as information regarding the anatomy of the thyroid gland, presence of cysts, and presence of additional thymic tissue within the empty thyroid area.

Accuracy of ultrasonography to establish the diagnosis and aetiology of permanent primary congenital hypothyroidism

OBJECTIVE

To compare ultrasonography and 99mTc thyroid scintigraphy for the aetiologic diagnosis of permanent congenital hypothyroidism (CH).

STUDY DESIGN

Eighty-eight consecutive patients with CH were recruited at an endocrinology outpatient clinic and submitted to high-frequency ultrasonography and to 99mTc scintigraphy.

RESULTS

Seventy-six patients were diagnosed with permanent CH and 12 with transitory CH. The agreement between ultrasound and scintigraphy was very high (kappa coefficient = 0.866; P < 0.001) for the entire group. In permanent CH patients, ultrasonography identified 67 cases of dysgenesis (absence of thyroid gland in the usual anatomical location in 66 and hemiagenesis in one), and this diagnosis was confirmed by scintigraphy (absence of functional thyroid tissue in 43 and ectopia in 24). In the other nine permanent CH patients, the thyroid was in the usual anatomical location on ultrasonography but scintigraphy did not identify functional tissue in one patient. In the 12 transitory CH patients, a normally shaped thyroid was detected by ultrasound in the usual location, whereas scintigraphy showed absence of functional tissue in two identical twins and scarce concentration of isotope in a third patient.

CONCLUSION

Ultrasonography is an accurate method to establish the presence of dysgenesis and might be used as the first imaging tool in patients with CH, whereas scintigraphy should be used mainly to distinguish agenesis from ectopia. Further examination is required to differentiate permanent CH with a normally located and shaped gland from transitory hypothyroidism.