Thyroid sonoelastography in paediatrics: A comparison between healthy and diffuse thyroid disease

Abstract

Introduction:

Shear wave elastography has been increasingly used as a supplementary tool to assess diffuse thyroid disease. This study aimed to evaluate thyroid shear wave velocity in healthy children, determine the optimal number of shear wave velocity measurements and establish a diagnostic cut-off value to aid in the detection of diffuse thyroid disease.

Methods:

We retrospectively analysed children (<16 years) who underwent thyroid ultrasound between 2019 and 2021. Both those with and without thyroid pathology were included consecutively. Shear wave elastography was performed, and 6 and 10 shear wave velocity measurements (m/s) were obtained from the right and left lobes, respectively. Analyses included Student’s t-test, Pearson’s correlation, receiver operating characteristic curve and Fagan nomogram.

Results:

Of 194 children, 144 controls had normal ultrasound findings, while 50 diffuse thyroid disease cases showed echostructural abnormalities in 84%. Shear wave velocity was higher in the diffuse thyroid disease group (2.09 ± 0.34 (1.42–2.88) m/s) than controls (1.75 ± 0.21 (1.38–2.47) m/s) (p < 0.001). The area under the curve was 0.805 ± 0.041 (0.725–0.884); shear wave velocity < 1.75 m/s was associated with a low probability of diffuse thyroid disease (8% (4–14%)). Accuracy fell significantly when measurements were reduced from 10 to 6 (p < 0.001). No laboratory tests confirmed euthyroid status in controls.

Conclusions:

Ten shear wave velocity measurements were recommended for optimal shear wave elastography evaluation. A shear wave velocity < 1.75 m/s suggested a low probability of diffuse thyroid disease.

Keywords

Sonoelastography shear wave velocity thyroid elasticity paediatric thyroid diseases shear wave measurement

Keypoints

Shear wave elastography (SWE) provides information on the elasticity of thyroid parenchyma, and it is a useful tool that supports a diffuse thyroid disease (DTD) diagnosis.

Children with shear wave velocity (SWV) < 1.75 m/s have a high probability of not having DTD.

Reducing the number of SWV measurements from 10 to 6 is not recommended, given the heterogeneity of the elasticity of the thyroid parenchyma.

Introduction

In paediatric patients, diffuse thyroid disease (DTD) comprises pathological processes affecting the entire thyroid gland, resulting in generalised enlargement (diffuse goitre) and/or functional impairment, rather than focal lesions or nodules. The most common aetiologies are autoimmune disorders, particularly Hashimoto’s thyroiditis (HT) and Graves’ disease (GD).^1–4

HT is the most common DTD in paediatric populations.^3,5–9 It is marked by progressive lymphocytic infiltration of the thyroid gland, with various levels of interstitial fibrosis, which reduces the elasticity of the thyroid gland, ultimately impairing hormone synthesis. In iodine-sufficient regions, it stands as the leading cause of acquired hypothyroidism and goitre in the paediatric population. The disorder exhibits a pronounced female predominance (approximately 4:1) and often clusters in families with autoimmune thyroid disease or other immune-mediated conditions such as type 1 diabetes, celiac disease and vitiligo.^4,10–12 Patients typically present with a firm, non-tender goitre and thyroid function at diagnosis may span from euthyroidism to subclinical or overt hypothyroidism; an initial, transient thyrotoxic phase is occasionally observed. Serological evaluation reveals elevated anti-thyroid peroxidase and/or anti-thyroglobulin antibodies, while ultrasound characteristically demonstrates a heterogeneous, hypoechoic thyroid parenchyma.^4,10–14

If left untreated, hypothyroidism can compromise linear growth, delay pubertal milestones and, in severe cases, impair neurocognitive development. Levothyroxine replacement – titrated to achieve age-appropriate thyroid-stimulating hormone and free thyroxine levels – remains the cornerstone of therapy. Because children initially euthyroid often progress to hypothyroidism over time, longitudinal monitoring of thyroid function is essential.^{4,11,13,15,16} GD in paediatrics is an autoimmune disorder characterised by the production of thyrotropin receptor–stimulating antibodies (TRAb), which stimulate the thyroid gland to synthesise and secrete excess thyroid hormones, resulting in hyperthyroidism and goitre.^2,4,17 It is the most common cause of hyperthyroidism in children, with peak incidence in adolescence and a female predominance. The pathogenesis involves a loss of immune tolerance to thyroid antigens, most notably the thyroid-stimulating hormone (TSH) receptor, leading to unregulated thyroid hormone production.^2,4

Clinical presentation in children often includes behavioural changes (irritability, emotional lability and decline in school performance), tachycardia, tremor, increased appetite, weight loss, heat intolerance and goitre. Ophthalmopathy occurs in up to 40% of paediatric cases but is typically milder than in adults. Growth acceleration and advanced bone age may be seen, although puberty is often delayed.²

Diagnosis is confirmed by suppressed TSH, elevated free T4 and T3, and positive TRAb or thyroid-stimulating immunoglobulins. The American Thyroid Association defines hyperthyroidism as a form of thyrotoxicosis due to inappropriately high synthesis and secretion of thyroid hormone(s) by the thyroid, with GD being the leading aetiology in children.²

GD in paediatrics is frequently associated with other autoimmune conditions and genetic syndromes such as Down syndrome and Turner syndrome. The disease is rare in very young children, and diagnosis may be delayed due to nonspecific symptoms or misattribution to behavioural disorders.²

Ultrasound plays an essential role in the diagnosis of DTD by enabling real-time assessment of thyroid parenchymal features such as echogenicity, echotexture, gland size, margins and vascularity. High-resolution ultrasound can reliably differentiate normal thyroid tissue from DTD, with features such as decreased or increased echogenicity, coarse echotexture, increased anteroposterior diameter, lobulated margins and increased vascularity being significantly associated with DTD.^18–20 Multiparametric approaches, including B-mode, Doppler and elastography, further enhance diagnostic accuracy and can help distinguish between aetiologies such as GD and HT.²¹

Ultrasound findings inform patient management by identifying the presence and extent of DTD, distinguishing between diffuse and nodular disease. Ultrasound is used in conjunction with blood tests – including TSH, free T4 and thyroid autoantibodies – to correlate structural and functional findings. While laboratory tests establish thyroid function and autoimmune status, ultrasound provides anatomical and vascular information, and the combination improves diagnostic confidence and guides management decisions.^19,22 More severe thyroid dysfunction is associated with higher grades of echogenicity and heterogeneity on ultrasound in autoimmune DTD.²² Thus, ultrasound and serologic testing are complementary in the comprehensive evaluation and management of diffuse thyroid disease.

On B-mode ultrasound, both HT and GD typically show a diffusely hypoechoic and heterogeneous thyroid gland, so echotexture alone cannot reliably distinguish between the two.^2,23,24 HT may also show increased fibrosis and atrophy in chronic cases.²⁴

Colour Doppler and power Doppler are more useful tools for differentiation. GD is characterised by diffusely and markedly increased vascularity (‘thyroid inferno’), with high peak systolic velocities (PSV) in the inferior or superior thyroid arteries, often >50 cm/s.^{21,23,25–28} In contrast, HT usually shows normal or mildly increased vascularity, with lower PSV values (typically <30 cm/s).^23,26,28 However, HT can occasionally show focal areas of increased flow, but not the diffuse ‘inferno’ pattern seen in GD.^23,29

Quantitative Doppler parameters are helpful: PSV > 50 cm/s in the superior or inferior thyroid artery strongly favours GD, while lower values suggest Hashimoto’s or other thyroiditis.^27,28 Superb microvascular imaging and vascularity index (VI) can further improve accuracy, with higher VI in GD compared with HT.³⁰

Modern ultrasound machines now incorporate elastography techniques, enabling the assessment of tissue stiffness. Ultrasound elastography has become an essential tool in clinical practice, offering both qualitative and quantitative insights into tissue stiffness.³¹

Elastography in paediatric thyroid ultrasound provides additional information to conventional ultrasound for the evaluation of thyroid nodules and diffuse thyroid diseases. In children, elastography can help differentiate benign from malignant thyroid nodules, as malignant nodules tend to be stiffer and thus have higher strain ratios or shear wave velocity (SWV) compared with benign lesions.^32–36 This adjunctive value is particularly relevant because paediatric thyroid nodules have a higher malignancy risk than those in adults, and non-invasive risk stratification is critical to guide the need for fine-needle aspiration biopsy.^33,34,36 Elastography aids in the evaluation of diffuse thyroid diseases such as HT, where increased stiffness correlates with disease presence and severity, and can distinguish affected glands from normal thyroid tissue.^37–40

Ultrasound elastography techniques can be broadly classified into two main categories: strain elastography and shear wave elastography (SWE).

- Strain elastography (SE) assesses tissue deformation (strain) in response to an applied force, which may be generated through manual compression or physiological motion. Strain is inversely correlated with tissue stiffness. SE provides qualitative or semi-quantitative insights into tissue.^41,42

- SWE generates shear waves within the tissue via an acoustic radiation force impulse. The propagation speed of these waves is measured, as they travel more rapidly through stiffer tissues. SWE can be further subdivided into:

- Transient elastography utilizes a mechanical vibrator to generate low-frequency shear waves, measuring their speed to estimate tissue stiffness. This technique is widely employed for liver stiffness assessment.^43,44

- Point shear wave elastography (pSWE) uses a focused ultrasound beam to produce shear waves at a specific point, providing a quantitative measurement of tissue stiffness at that location.⁴⁵

- Two-dimensional shear wave elastography (2D-SWE) generates shear waves across a broader region, producing a two-dimensional map of tissue stiffness. This approach offers more comprehensive spatial data compared with pSWE.⁴⁵ 2D-SWE, which provides a real-time colour elastogram, can be used to determine SWV in multiple areas.^41,46

The reliability of SWE in thyroid assessment has been well established. Numerous studies have highlighted its potential in distinguishing benign from malignant thyroid nodules.^47,48 However, elastography should be considered complementary to, not a replacement for, conventional ultrasound and cytological assessment, as its diagnostic thresholds and reproducibility in paediatrics are still being refined.^32,36

European guidelines recommend the use of elastography in thyroid ultrasound for assessment because elastography provides additional, non-invasive information about tissue stiffness, which improves the risk stratification of thyroid nodules and helps differentiate benign from malignant lesions. Elastography, when combined with conventional ultrasound and TIRADS classification, increases diagnostic sensitivity and specificity for malignancy, particularly in nodules with indeterminate cytology or equivocal ultrasound features. Based on current evidence, elastography enhances the stratification of patients for fine-needle aspiration, thereby minimizing the frequency of unnecessary invasive procedures. This approach is supported by European expert consensus and a growing body of literature.^2,49–55 Nevertheless, its utility in the evaluation of DTD remains less clearly defined.^54,56–58 Despite its potential in assessing diffuse thyroid disorders such as HT and subacute thyroiditis, the widespread adoption of elastography for this purpose is constrained by its operator-dependent nature and the absence of standardised reporting protocols.^54,57 These factors significantly limit its broader clinical utility in DTD.^56,58

At our institution, SWE is routinely employed in thyroid ultrasonography, owing to its ability to provide complementary diagnostic information in the evaluation of thyroid nodules and the thyroid parenchyma in cases of DTD, while preserving time efficiency.

Variations in thyroid elasticity have been described in relation to thyroid hormone concentrations and gland volume, with age being a significant factor. However, the precise effects of hormonal fluctuations on thyroid elasticity remain insufficiently understood. Thyroid elastography has been shown to change according to hormonal status and may vary across different paediatric age groups.^5,38 There is a limited number of studies available to establish normative reference values for elastographic measurements in paediatric populations across different age groups.

Agarwal et al.³⁸ identified significant differences in SWE values between children with newly diagnosed HT and healthy controls, with these values correlating with serum thyroid hormone concentrations. Furthermore, Hazem et al.³⁷ demonstrated that SWE could effectively distinguish normal thyroid tissue from various types of DTD in paediatric patients.

In addition, Koca and Seber observed a progressive increase in SWE scores corresponding to the severity of thyroiditis stages in children with HT, suggesting that thyroid stiffness, as measured by elastography, is influenced by both disease stage and hormonal status.³⁹ These findings indicate that thyroid elastography values may indeed fluctuate based on age and hormonal changes in paediatric populations.^38,39

Understanding the normal range of thyroid elasticity is essential for helping in the detection of DTD. However, studies on thyroid elastography in paediatric populations remain limited, and widely validated cut-off values have yet to be established.

This study aims to determine SWV in healthy children, assess the optimal number of SWV measurements and establish a cut-off value for diagnosing DTD.

Methods

This retrospective study was conducted following the approval of the Virgen de la Arrixaca Clinical Hospital Ethics Committee. Thyroid elastography is an integral component of the Radiology Service at our institution, providing valuable adjunctive support for diagnostic evaluations. Parental or legal guardian oral consent was obtained for the processing and use of data in subsequent studies.

Between September 2019 and February 2021, paediatric patients from our institutional database who had undergone ultrasound evaluations due to abnormal thyroid function test results were retrospectively identified and assigned to the DTD group. The control group was composed of children selected from the same database and time frame, who had undergone an ultrasound for non-thyroid-related clinical indications and had no known thyroid pathology. Parents or legal guardians provided informed consent for an additional thyroid ultrasound, performed exclusively for research purposes and separate from the clinically indicated examination. Exclusion criteria encompassed individuals older than 16 years, those with a history of thyroid surgery and cases of non-cooperative behaviour resulting in substantial motion artefacts in SWE.

Imaging protocol

All ultrasound assessments were performed by a radiologist with more than 7 years of experience in SWE. Imaging was conducted using an ACUSON S3000 ultrasound system (Siemens Healthcare, Erlangen, Germany) equipped with a linear probe (frequency range: 7–12 MHz) for thyroid sonography and 2D-SWE.

Patients underwent cervical ultrasound in the supine position with hyperextension of the neck. Three SWV measurements were obtained from each thyroid lobe – three from the right lobe and three from the left – resulting in a total of six measurements across the entire thyroid parenchyma. In a separate approach, five SWVs were obtained from the right lobe and five from the left, yielding a total of ten measurements. Both shear SWV measurements were obtained from each thyroid lobe in the longitudinal plane, aiming to assess the elasticity of most of the lobe. To ensure measurement reliability, a quality map was employed for verification (Figures 1 and 2).

Figure 1.

Shear wave elastography examination from the right thyroid lobe in a healthy volunteer showing the colour box containing the five regions of interest (ROI) with a mean SWE measurement of 1.86 m/s (calculated from five measurements).

Figure 2.

Quality map made on a longitudinal ultrasound section of the right thyroid lobe that shows a high level of confidence regarding the technique performed, represented in green on the colour scale.

The region of interest (ROI) was standardised at 0.5 × 0.5 cm.

The sampling volume was generally positioned over the thyroid gland, aiming to encompass most of its structure to obtain a reliable representation of parenchymal elasticity in both cases and controls. It was not placed over nodules, as no well-defined nodules were identified in the case group.

In addition, thyroid echostructure and glandular volume were documented using the following formula (excluding the isthmus):

Thyroid volume = length × width × height × 0.52

Data collection

All clinical and imaging data were obtained by the radiologist overseeing the study. Recorded variables included participants’ age, sex, weight and height. In DTD group, the presence of hypo- or hyperthyroidism, along with thyroid autoantibodies (thyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPOAb), was documented). Thyroid ultrasound assessments included gland volume (cm³) and the presence of echostructural abnormalities (yes/no). SWV measurements (m/s) were obtained from three ROI per lobe (six total) or five per lobe (ten total), alongside depth (cm).

Statistical analysis

Statistical analyses were conducted using the Statistical Package for the Social Sciences software for Windows (version 24.0, IBM).

Descriptive statistics were employed to characterise the distribution of variables, including frequency analyses and the computation of key quantitative parameters (mean, standard deviation, maximum and minimum values).

Inferential statistical analyses included Student’s t-test, which was employed to compare quantitative variables as well as dichotomous qualitative variables, and Pearson’s correlation, which was utilized to examine relationships between continuous variables.

The impact of acquiring 6 versus 10 SWV measurements was assessed using Student’s t-test. In addition, the same statistical test was applied to analyse differences in SWV based on sex, health status (healthy vs diseased), glandular echostructure and the presence of TgAb and TPOAb.

Pearson’s correlation test was applied to assess the relationship between SWV and various physiological parameters, including age, weight, height, thyroid volume and depth.

Furthermore, a receiver operating characteristic (ROC) curve was constructed to evaluate diagnostic performance, and a Fagan nomogram was utilized to estimate the post-test probability of DTD based on SWV measurements in both the control and DTD groups.

Results

A total of 194 children (mean age: 8.79 ± 3.7 years; range: 1–16 years) were included in the study, of whom 106 were girls. The DTD group consisted of 50 patients, while the control group comprised 144 healthy volunteers. Table 1 presents the ultrasound characteristics (glandular volume and structure) and elastography parameters (SWV and measurement depth) of the thyroid gland.

Table 1.

Demographic, thyroid volume, sonographic and SWE data.

	Entire sample (n = 194)	DTD (n = 50)	Healthy (n = 144)	p
Age (years)	8.79 ± 3.71	10.98 ± 3.61	8.02 ± 3.44	<0.001
BMI	20.19 ± 13.95	23.34 ± 18.25	18.96 ± 11.76	0.81
Volume RTL (cm³)	2.66 ± 2.67	4.85 ± 4.21	1.88 ± 1.06	<0.001
Volume LTL (cm³)	2.33 ± 2.26	4.35 ± 3.41	1.59 ± 0.93	<0.001
Total volume (cm³)	4.87 ± 4.61	8.86 ± 7.08	3.42 ± 1.86	<0.001
Depth 5 measurements in RTL	1.27 ± 0.29	1.31 ± 0.29	1.26 ± 0.30	0.292
Depth 5 measurements in LTD (cm)	1.28 ± 0.33	1.38 ± 0.47	1.25 ± 0.26	0.016
Depth 10 measurements (cm)	1.47 ± 0.22	1.61 ± 0.25	1.42 ± 0.19	0.016
Abnormality of the echostructure	42	42 (84%)	0	0.011
SWV 5 measurements in RTL	1.83 ± 0.32	2.05 ± 0.38	1.75 ± 0.26	<0.001
SWV 3 measurements in RTL	1.82 ± 0.34	2.05 ± 0.39	1.75 ± 0.28	<0.001
SWV 5 measurements in LTL	1.85 ± 0.33	2.13 ± 0.38	1.75 ± 0.25	<0.001
SWV 3 measurements in LTL	1.83 ± 0.35	2.13 ± 0.41	1.73 ± 0.26	<0.001
SWV 10 measurements both lobes	1.84 ± 0.29	2.09 ± 0.34	1.75 ± 0.21	<0.001
SWV 6 measurements both lobes	1.83 ± 0.30	2.09 ± 0.35	1.75 ± 0.21	<0.001

BMI: Body mass index; RTL: right thyroid lobe; LTD: left thyroid lobe, SWV: shear wear velocity.

Significant differences were observed between groups assessed with 6 versus 10 SWV measurements, both globally and after stratification into healthy and diagnosed cases (p < 0.001). SWV values were consistently higher in the group assessed with 10 measurements compared with the group with 6 measurements (Table 1). Consequently, the mean SWV derived from 10 measurements was adopted for subsequent statistical analyses.

The mean SWV was notably elevated in the DTD group (2.09 ± 0.34 m/s (1.42–2.88)) compared with the healthy control group (1.75 ± 0.21 m/s (1.38–2.47) p < 0.001). In addition, across both case and control groups, SWV was higher in girls (1.89 ± 0.3 m/s (1.38–2.88)) compared with male participants (1.78 ± 0.27 m/s (1.39–2.68); p = 0.007).

A positive correlation between the mean SWV and age was obtained (r = 0.266, p < 0.001), as well as weight and height with SWV (r = 0.359 and r = 0.388, p < 0.001) (Table 2). If the state of health of the patient was considered (healthy vs diagnosed), positive correlations were also obtained between SWV and weight and height, as well as between the SWV values and the volume of the thyroid gland, in both healthy (r = 0.415, p < 0.001) and diagnosed children (r = 0.573, p < 0.001) (Table 2).

Table 2.

Correlation between SWV with demographic data and thyroid volume, with a distinction between healthy, diagnosed and total population. SWV: total mean of both thyroid lobes (10 measurements).

Correlation analysis	DTD (50)	Healthy (144)	Entire sample (194)	p: DTD, healthy and entire sample.
SWV and age	0.168	0.485	0.266	0.239: <0.001 and 0.001
SWV and volume	0.573	0.415	0.658	<0.001: <0.001 and <0.001
SWV and weight	0.039	0.374	0.359	0.793: <0.001 and <0.001
SWV and BMI	−0.097	−0.002	0.035	0.538: 0.981 and 0.663
SWV and height	0.06	0.43	0.388	0.698: <0.001 and <0.001
SWV and depth	0.936	0.884	0.934	<0.001: <0.001 and <0.001

SWV: shear wear velocity.

A positive correlation was found between SWV and depth to the skin (r = 0.934, p < 0.001). The thyroid glands with a heterogeneous echostructure showed higher velocities, with a SWV of 2.15 ± 0.32 m/s, as compared to 1.75 ± 0.22 m/s in thyroid glands with a homogeneous structure (p = 0.011).

Of the 50 patients in the DTD group, 37 showed positive TPOAb results, while 13 showed negative results. The TgAb results were positive in 36 patients and negative in 14. In the patients with positive TPOAb results, the SWV was higher, with a mean SWV of 2.14 ± 0.3 m/s, as compared to 1.88 ± 0.31 m/s in patients with negative TPOAb results. The patients with positive TgAb values also showed a higher SWV, with a mean SWV of 2.2 ± 0.28 m/s, as compared with a mean SWV de 1.81 ± 0.31 m/s of patients with negative TgAb results (p < 0.005).

The performance of the SWE was assessed with a ROC curve which visually represents the effectiveness of a test or model in distinguishing between different diagnostic conditions. It is created by plotting sensitivity (true positive rate) on the vertical axis and 1-specificity (false positive rate) on the horizontal axis for a range of threshold values. This curve illustrates the test’s ability to differentiate between categories, such as individuals with and without a disease.^59,60

The area under the ROC curve provides a numerical summary of the test’s discriminatory power. A value of 1.0 signifies perfect separation between groups, while 0.5 indicates no distinction, equivalent to random guessing. ROC curves help determine the best cut-off point for decision-making.⁶¹

SWE demonstrated an area under the curve (AUC) of 0.805 ± 0.41, with a range of 0.725 to 0.884. The mean AUC of 0.805 suggests a moderately strong ability to differentiate between conditions, while the standard deviation (±0.41) accounts for variability in this estimation due to sample characteristics or methodological constraints. The reported range of 0.725 to 0.884 likely represents a confidence interval, indicating the probable limits within which the true AUC value falls, considering inherent uncertainties in data collection and analysis.

A diagnostic threshold of 1.75 m/s was established for DTD, indicating that values exceeding this cut-off were associated with a greater probability of DTD presence. Furthermore, key diagnostic performance metrics were calculated, yielding sensitivity (S) = 0.86, specificity (SP) = 0.58, positive predictive value(PPV) = 0.42 and negative predictive value (NPV) = 0.92 (Figure 3).

Figure 3.

ROC curve shows the performance of the SWE for values of SWE < 1.75 m/s. The area under the curve far from the diagonal line of equality shows that SWE is better than the chance at predicting DTD.

For a 95% confidence interval (CI = 0.12–0.48), the Fagan nomogram indicated a negative likelihood ratio of 0.24, corresponding to a posterior probability (odds) of 8% (95% CI = 4–14). In addition, it yielded a positive likelihood ratio of 2.06 (95% CI = 1.65–2.58) and an associated posterior probability of 42% (95% CI = 36–47) (Figure 4).

Figure 4.

The Fagan nomogram illustrates how SWV influences the probability of thyroid disorders. For a patient with a pre-test probability of 26%, a positive result – defined by SWV either above or below the indicative threshold of 1.75 m/s – increases the post-test probability to 40%. Conversely, a negative result reduces the probability to 8%, underscoring its diagnostic significance.

The Fagan nomogram is a graphical tool employed in clinical decision-making to estimate the post-test probability of a disease based on a given pre-test probability and the likelihood ratio of a diagnostic test. It consists of three parallel scales: pre-test probability, likelihood ratio and post-test probability. By drawing a line through the known pre-test probability and likelihood ratio, clinicians can determine the corresponding post-test probability at the intersection with the final scale, facilitating evidence-based diagnostic evaluation.⁶²

Discussion

Ultrasound remains the imaging modality of choice for evaluating thyroid pathologies.

SWE – integrated into most modern ultrasound platforms – has emerged as a key advancement in thyroid imaging, providing quantitative assessment of tissue stiffness that improves the detection and characterization of DTD.^54,57 In addition to its role in DTD evaluation, elastography contributes substantially to thyroid nodule assessment by refining malignancy risk stratification and potentially reducing the need for unnecessary invasive procedures such as fine‑needle aspiration.^{49,55,63–65}

Despite these advantages, its broader integration into routine practice remains limited, largely due to operator‑dependent variability and the absence of universally accepted reporting standards.^54,57,66

These factors significantly limit its broader clinical utility in diffuse thyroid disease.^58,67

At our institution, SWE is routinely incorporated into thyroid ultrasonography due to its capacity to furnish complementary diagnostic insights for the assessment of thyroid nodules and the thyroid parenchyma in cases of DTD, while maintaining procedural efficiency.^{39,47,48,54,57}

Elastography can be used to differentiate between HT and GD in paediatric patients by quantitatively assessing thyroid tissue stiffness, with GD typically showing higher SWE values than HT. Studies in children and adolescents demonstrate that mean SWE values are significantly elevated in GD compared with HT, with reported mean values around 17.3 kPa for Graves’ disease and 15.3 kPa for HT and a suggested cut-off of 17.8 kPa to distinguish GD from HT.^37,68

The underlying pathophysiology accounts for these differences: GD is characterised by diffuse hyperplasia and increased vascularity, resulting in greater tissue stiffness, while HT involves lymphocytic infiltration and fibrosis, which also increases stiffness but to a lesser degree.^37,68,69 Elastography is thus a reliable, non-invasive adjunct to conventional ultrasound and laboratory testing for differentiating these autoimmune thyroid diseases in children, especially when clinical and serological findings are inconclusive.^37,68

However, the aim of this study was not to distinguish between HT and GD, but to establish a diagnostic cut-off value for detecting DTD, encompassing both conditions. Larger studies may be required to enable clearer differentiation, ideally controlling for potential confounding factors such as age, sex and thyroid volume. Elastography provides valuable quantitative data, yet should be interpreted alongside clinical, laboratory and imaging findings, as stiffness values may overlap, particularly in advanced or atypical cases.^37,68–70

This study employs 2D-SWE to assess thyroid gland elasticity in paediatric populations, including both healthy children and those with hyperthyroidism or hypothyroidism secondary to DTD. 2D-SWE was established as a diagnostic tool for DTD, with a SWV threshold of ⩾1.75 m/s. In patients with a pre-test probability of 26% for DTD, a positive test increases this likelihood to 42%, while a negative test reduces it to 8% (sensitivity = 0.86, specificity = 0.58, PPV = 0.42, NPV = 0.92). This suggests that patients with an SWV < 1.75 m/s have a low probability of DTD. To date, no prior paediatric studies have quantified the probability of DTD based on SWV values.

HT is characterised by lymphoid infiltration and variable interstitial fibrosis, while GD presents with follicular cell hypertrophy, lymphocytic infiltration, reduced colloid volume and hypervascularization. Patients with DTD demonstrate increased SWV, likely reflecting histological changes in thyroid tissue, particularly in cases with echostructural abnormalities. Although Sporea et al.³⁷ assert that 2D-SWE cannot differentiate between DTD subtypes, Hazem et al. propose specific SWV values for HT (15.31 ± 2.95 kPa) and GD (17.26 ± 4.2 kPa) in paediatric patients. Other studies, including those by Cepeha et al.⁸ and Fukuara et al.,⁷¹ have reported higher SWV values in DTD patients. However, limitations in sample size and methodology – such as axial-plane SWE measurements in Fukuara et al.’s study – may contribute to variability in findings.

In this study, SWV assessments were conducted using different numbers of measurement repetitions, revealing statistically significant variations when 6 instead of 10 fewer measurements were performed. This supports the recommendation against reducing the number of measurements. Prior studies have documented the impact of measurement frequency in adults,^7,14,72 but there is a lack of analogous paediatric research. In addition, SWV values were found to correlate positively with measurement depth (r = 0.6), yet no standardised protocol has been established to determine the optimal depth to skin for thyroid elastography.

Thyroid volume also correlated positively with SWV in both healthy and affected individuals. However, conflicting findings in existing literature suggest that sample size may influence this association.^5,8,37

SWV demonstrated significant variation across age, weight and height, with higher values observed in older, heavier and taller individuals. This trend is likely attributable to demographic differences between healthy participants and those diagnosed with DTD in this study. Specifically, patients with DTD exhibited greater age, weight and height compared with their healthy counterparts.^7,3,73

Sex-based differences in SWV were observed, with higher values recorded in girls (p = 0.007). DTD diagnosis was also more prevalent among girls, comprising 74% of diagnosed DTD patients, while overall, girls represented 54.6% of the study sample. Some studies, such as Habibi et al.,⁷⁴ found no significant sex-related differences, possibly due to a more balanced sample distribution (48.1% female participants). Studies with smaller sample sizes also failed to detect sex-based differences in SWV.^37,74,75

A positive correlation between age and SWV (r = 0.44) aligns with findings by Bakırtaş et al.,¹⁸ who attribute this relationship to age-related thyroid hormone variations and glandular growth. Notably, increased SWV was associated with elevated TSH levels and decreased free T3 and T4 levels in older paediatric patients.

Previous studies^8,71,76 have demonstrated that higher SWV values are correlated with positive thyroperoxidase antibody (TPOAb) results, suggesting a link between increased SWV and lymphocytic infiltration. While thyroglobulin antibodies (TgAb) were also associated with higher SWV in affected patients, their relationship with disease progression and fibrosis remains unclear. Some studies^8,9 have failed to establish an association between TgAb and SWV, potentially due to inclusion of patients with advanced immune responses and higher degrees of fibrosis.

Morphological alterations, including lobulated thyroid contours, altered echostructure, and hypoechogenicity, reflect chronic glandular damage and correspond to elevated SWV values. While these structural changes exhibit high specificity, their sensitivity remains limited. Nevertheless, combined assessment with elastography may enhance diagnostic accuracy for DTD.⁹

This study presents several limitations. The lack of age-based stratification and pathology-specific subgroup analyses may impact the generalizability of findings. In addition, the health status of control group participants was not fully verified, leaving the possibility of undiagnosed thyroid abnormalities. Future studies should aim to establish standardised SWE measurement protocols and further investigate factors influencing SWV variability in paediatric populations.

Conclusion

Thyroid SWE is a useful tool that can be used as a supporting marker for the diagnosis of DTD, as the SWV was higher in patients with the disease, with respect to the healthy ones. Patients with a mean value of SWV < 1.75 m/s have a small probability of having DTD. Finally, a recommendation is made to perform 10 SWV measurements in the thyroid gland and five in each thyroid lobe.

Footnotes

ORCID iD

Marta Tovar Pérez

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.

Ethical approval

The Virgen de la Arrixaca Clinical Hospital Ethic Committee approved this study at 24/09/24. Permission from patient(s) or subject(s) obtained in writing for publishing their case report is not applicable due this is not a case report. No permission was obtained in writing from patient or any person whose photograph was included for publishing their photographs and images, because publication of anonymized and de-identified ultrasound images does not need permission except when they are part of a case report, and this is not a case report. Reference number: 2024-7-12-HCUVA. Marta Tovar, as a guarantor, is aware that permission from a previous publisher for reproducing any previously published material will be required should your article be accepted for publication and will be responsible for obtaining that permission.

Permission from patient(s) or subject(s) obtained in writing for publishing their case report

Not applicable. This is not a case report.

Permission obtained in writing from patient or any person whose photograph is included for publishing their photographs and images

No. Publication of anonymized and de-identified ultrasound images does not need permission except when they are part of a case report and this is not a case report.

Confirm that you are aware that permission from a previous publisher for reproducing any previously published material will be required should your article be accepted for publication and that you will be responsible for obtaining that permission

Yes.

Contributors

Juan de Dios Berna Mestre

Luis Enrique Fernández Rodríguez

Regina María Sánchez Jiménez

Cristina Serrano García

Patricia Navarro Sánchez

Florentina Guzmán Aroca

Guarantor

Marta Tovar Pérez.

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