Serum thyroglobulin measurement. Utility in clinical practice

The diagnostic potential of two exosome-derived circRNAs for papillary thyroid cancer

BACKGROUND

As a critical component of exosomes, circular RNAs (circRNAs) have shown great value in cancer diagnosis. This study aimed to identify circRNAs in exosomes for the diagnosis of PTC (papillary thyroid carcinoma).

METHODS

We selected hsa_circ_0082002 and hsa_circ_0003863 based on circRNA microarray. The levels of exosomal hsa_circ_0082002 and hsa_circ_0003863 in the sera of healthy control (n = 68), benign thyroid tumors (n = 60), and PTC without and with Hashimoto's thyroiditis (n = 164) were quantified by qPCR (quantitative polymerase chain reaction). Receiver operating characteristic analyses were conducted to evaluate the diagnostic sensitivity and specificity. Bioinformatics databases were used to predict the microRNAs and proteins binding with hsa_circ_0082002 and hsa_circ_0003863.

RESULTS

The levels of exosomal hsa_circ_0082002 and hsa_circ_0003863 were positively associated and statistically increased in PTC compared to healthy and benign thyroid tumors. Intriguingly, higher levels of exosomal hsa_circ_0082002 and hsa_circ_0003863 were positively correlated with lymph node metastasis and vascular invasion in PTC. Further stability tests show that exosomal hsa_circ_0082002 and hsa_circ_0003863 could exist stably in sera treated by several freeze-thaw cycles at -20 °C and with a storage time shorter than 24 h at 4 °C. Furthermore, hsa_circ_0082002 and hsa_circ_0003863 were predicted to interact with microRNAs and proteins, suggesting that hsa_circ_0082002 and hsa_circ_0003863 might contribute to the occurrence and progression of PTC through interacting with microRNAs and RNA binding proteins.

CONCLUSION

Collectively, we identified two PTC-related circRNAs incorporated in exosomes and uncovered their potential as tumor markers to diagnose PTC, in particular, more aggressive PTC.

Preradioactive Iodine Thyroglobulin Levels as Predictors of Metastasis in Well-Differentiated Thyroid Carcinoma Patients

Objective The aim of this study was to determine the cut-off value of thyroglobulin (Tg) levels as a predictor of metastases in post total thyroidectomy patients with well-differentiated thyroid carcinoma (DTC).

Materials and Methods A retrospective case-control study with an observational diagnostic approach was done. Subjects were 102 DTC patients divided into a case group with metastases and a control group without metastases. Tg and antithyroglobulin antibody (ATA) levels on thyroid-stimulating hormone (TSH)-stimulated preradioactive iodine were compared with each other. Diagnosis of metastases was based on postradioactive iodine whole-body scan. The cut-off value for Tg preradioactive iodine and the area under the curve (AUC) were obtained from the receiver operating characteristic curve.

Result The characteristics and histopathological type of DTC among these two groups were not significantly different (p = 0.47). The Tg levels in the case and control groups were 106 (2.2–6,000) ng/mL and 2.7 (0.3–10.10) ng/mL, respectively (p = 0.0001). TSH level in the case group was 50 (30–107) µIU/mL and in the control was 50 (20–100) µIU/mL (p = 0.224). ATA levels in the case and control groups were 0–3,000 and 0–629 ng/mL, respectively (p = 0.01). The AUC was 0.976 with a 95% confidence interval of 0.924 to 0.996 and a standard error of 0.016. The cut-off value of preradioactive iodine Tg was 10.1 ng/mL or higher with sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 96.1, 100, 98.0, 100, and 96.2%, respectively.

Conclusion Preradioactive iodine Tg level 10.1 ng/mL or higher can be used as a predictor of metastasis in patients with DTC.

Circulating Biomarkers in Thyroid Cancer

Thyroid cancer is the most important endocrine cancer with increasing incidence. While thyroid cancers, especially papillary thyroid cancers, are known to exhibit generally a favorable outcome with excellent survival rates, some thyroid cancers are more aggressive with a poor prognosis. Several different biomarkers have been introduced for the diagnosis of disease, identification of tumor load, assessment of therapy response, and the detection of recurrence during follow-up of the thyroid cancer patients. This chapter gives a brief overview of the circulating biomarkers used in thyroid cancer patients.

Congenital multinodular goiter in a neonate presenting with airway obstruction

Background

Congenital goiter constitutes a rare cause of congenital neck masses. Goitrous enlargement can be associated with serious airway obstruction.

Case description

We report a term, girl baby with a large asymmetrical neck mass who presented on day 2 of life. Clinical examination revealed stridor and local examination showed an asymmetric nodular firm swelling with no signs of inflammation. The computerized tomography of the neck and fine needle aspiration cytology (FNAC) confirmed the swelling as being a multinodular goiter. The thyroid function test (TFT) was suggestive of hypothyroid status. Further investigations revealed the cause as being dyshormonogenesis probably secondary to a thyroglobulin synthetic defect. The baby was started on levothroxine supplementation (13 μg/kg/day); neck swelling markedly reduced with normalization of TFT over the next 3 weeks. To the best of our knowledge this is the first reported case of the presence of multinodularity in a baby with congenital goiter.

Surveillance for Differentiated Thyroid Cancer Recurrence

Serum thyroglobulin monitoring along with anatomic and functional imaging play key roles in the surveillance of patients with differentiated thyroid cancer after initial treatment. Among patients with a disease stage justifying thyroid remnant ablation or with suspected metastatic disease, radioiodine whole-body scans are essential in the months after surgery. For patients with low to moderate-risk cancers, ultrasonography of the neck (with measurement of serum thyroglobulin on thyroid hormone replacement) are the best initial diagnostic modalities, and are often the only tests required. In individuals suspected of having distant metastases, CT, MRI, and 18F-FDG PET can make important contributions in localizing residual disease and monitoring its progression and responses to therapy, provided they are used in the appropriate setting.

Monitoring differentiated thyroid cancer patients with negative serum thyroglobulin

Aim: Serum antithyroglobulin antibody (TgAb) has been reported as a surrogate marker for differentiated thyroid cancer (DTC) in some conditions. We investigated changes in serum TgAb levels after stimulation with thyroid- stimulating hormone (TSH) and the clinical implications for monitoring DTC. Patients, methods: We retrospectively enrolled 53 DTC patients who had undergone total thyroidectomy and were negative for serum Tg and positive for TgAb. Patients underwent highdose radioactive iodine treatment, and serum TgAb was measured before (TgAbBAS) and after TSH stimulation (TgAbSTIM). TgAb was followed up 6 to 12 months later (TgAbF/U). The change in TgAb after TSH stimulation ΔTgAb- STIM) was calculated as a percentage of the baseline level. Patient disease status was classified into no residual disease (ND) and residual or recurred disease (RD) by follow-up imaging studies and pathologic data. The characteristics and diagnostic value of serum TgAb levels and ΔTgAbST|M were investigated with respect to disease status. Results: 38 patients were in the ND group and 15 were in the RD group. TgAbBAS, TgAbSTIM and TgAbF/U were significantly higher in the RD compared to the ND group (p = 0.0008, 0.0002, and < 0.0001, respectively). ΔTgAbSTIM was also significantly higher in the RD group (p = 0.0009). In the patients who presented with obviously high (> 50%) or low (< -50%) ΔTgAbSTIM, the proportions in the RD group were markedly different at 100% and 7%, respectively. ΔTgAbSTIM had significant diagnostic value for RD (p < 0.001). Conclusion: The change in serum TgAb level after TSH stimulation is different between the RD and ND groups, and thus, it may be used as a surrogate diagnostic marker for DTC when the serum Tg is negative and TgAb is positive.

Hypothalamus-Pituitary-Thyroid Axis

The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.

Thyroid Remnant Estimation by Diagnostic Dose (131)I Scintigraphy or (99m)TcO4(-) Scintigraphy after Thyroidectomy: A Comparison with Therapeutic Dose (131)I Imaging

In this clinical study, we have compared routine diagnostic dose ¹³¹I scan and ^99mTcO₄⁻ thyroid scintigraphy with therapeutic dose ¹³¹I imaging for accurate thyroid remnant estimation after total thyroidectomy. We conducted a retrospective review of the patients undergoing total thyroidectomy for differentiated thyroid carcinoma (DTC) and subsequently receiving radioactive iodine (RAI) treatment to ablate remnant thyroid tissue. All patients had therapeutic dose RAI whole body scan, which was compared with that of diagnostic dose RAI, ^99mTcO₄⁻ thyroid scan, and ultrasound examination. We concluded that therapeutic dose RAI scan reveals some extent thyroid remnant in all DTC patients following total thyroidectomy. Diagnostic RAI scan is much superior to ultrasound and ^99mTcO₄⁻ thyroid scan for the postoperative estimation of thyroid remnant. Ultrasound and ^99mTcO₄⁻ thyroid scan provide little information for thyroid remnant estimation and, therefore, would not replace diagnostic RAI scan.

Radioiodine Scan Index: A Simplified, Quantitative Treatment Response Parameter for Metastatic Thyroid Carcinoma

PURPOSE

We aimed to develop and validate a simplified, novel quantification method for radioiodine whole-body scans (WBSs) as a predictor for the treatment response in differentiated thyroid carcinoma (DTC) patients with distant metastasis.

METHODS

We retrospectively reviewed serial WBSs after radioiodine treatment from 2008 to 2011 in patients with metastatic DTC. For standardization of TSH simulation, only a subset of patients whose TSH level was fully enhanced (TSH > 80 mU/l) was enrolled. The radioiodine scan index (RSI) was calculated by the ratio of tumor-to-brain uptake. We compared correlations between the RSI and TSH-stimulated serum thyroglobulin (TSH_s_Tg) level and between the RSI and Tg reduction rate of consecutive radioiodine treatments.

RESULTS

A total of 30 rounds of radioiodine treatment for 15 patients were eligible. Tumor histology was 11 papillary and 4 follicular subtypes. The TSH_s_Tg level was mean 980 ng/ml (range, 0.5-11,244). The Tg reduction rate after treatment was a mean of -7 % (range, -90 %-210 %). Mean RSI was 3.02 (range, 0.40-10.97). RSI was positively correlated with the TSH_s_Tg level (R(2) = 0.3084, p = 0.001) and negatively correlated with the Tg reduction rate (R(2) = 0.2993, p = 0.037). The regression equation to predict treatment response was as follows: Tg reduction rate = -14.581 × RSI + 51.183.

CONCLUSIONS

Use of the radioiodine scan index derived from conventional WBS is feasible to reflect the serum Tg level in patients with metastatic DTC, and it may be useful for predicting the biologic treatment response after radioiodine treatment.

Tg in Adults as a Sensitive Biomarker of Iodine Status: A 5-Year Follow up Population Study in Different Levels of Iodine Intake Regions

This study was to evaluate the usefulness of serum thymoglobulin (Tg) in adults to assess iodine status through a 5-year cohort study which was conducted in three regions with different levels of iodine intake: mild deficiency, more than adequate, and excess, from 1999 to 2004 in China. A total of 3099 subjects over 14 years old with normal serum levels of Tg in 1999 were eligible, of whom 2448 were followed in 2004. Serum levels of thyroid hormones and thyroid autoantibodies as well as urine iodine were measured, and B-mode ultrasonography of the thyroid was performed. A general linear model was performed to determine the determinant factors of serum Tg. Among subjects with mildly deficient iodine intake, those with more than adequate intake, and those with excessive intake, the baseline levels of serum Tg were substantially different (7.5μg/L, 5.9μg/L, and 6.8μg/L respectively, P<0.01), which were associated with age, sex, the rate of positive TgAb, abnormal thyroid volume, abnormal TSH, and positive personal history of thyroid diseases. The data from 1856 subjects with normal range of thyroid parameters but no personal history of thyroid diseases were analyzed to clarify the effect of iodine intake on Tg. Among these three regions, the serum Tg levels were substantially different in both 1999 and 2004, with a similar pattern for increased Tg (ΔTg) (3.1μg/L, 2.5μg/L and 3.5μg/L respectively, P<0.01). The general linear model analysis revealed that age, Tg, and baseline TSH levels were the determinants of ΔTg besides iodine intake. In conclusion, serum Tg in adults, resulting from a time-accumulative effect of iodine exposure, is a useful biomarker of regional iodine intake.

The role of ultrasound in the follow-up of children with differentiated thyroid cancer

BACKGROUND

Thyroid cancer is the most common endocrine malignancy with relatively good prognosis in children. However, unlike adults, children usually present with more advanced disease and have a higher local recurrence and distant metastases. Thus surveillance for recurrence is a major goal of long-term follow-up.

OBJECTIVE

This retrospective study evaluates the diagnostic value of ultrasound (US) imaging in the post-therapy surveillance of children with differentiated thyroid cancer.

MATERIALS AND METHODS

We reviewed the charts of 54 children (40 girls; mean age 14.3 ± 3.6 years) with differentiated thyroid cancer treated with total or near-total thyroidectomy. Forty children (29 girls and 11 boys) who had routine follow-up US examinations (112 studies) were included for the evaluation of US accuracy in the follow-up of pediatric differentiated thyroid cancer. Histopathology, stimulated thyroglobulin determination, post-therapy whole-body iodine scan and clinical follow-up were used as the standards of reference.

RESULTS

Mean period of follow-up was 34 months. The frequency of recurrence was 42% (17/40). Seventeen percent of the children had lung metastases either at presentation or on follow-up. In all cases of lung metastases, stimulated thyroglobulin level was greater than 10 ng/ml. The sensitivity was 85.7%, specificity 89.4%, negative predictive value 94.4% and positive predictive value 75% for US in detecting loco-regional recurrence in follow-up studies of pediatric differentiated thyroid cancer. In 17.3% (18/104) of studies, the results of stimulated thyroglobulin and US were discordant.

CONCLUSION

US showed very good sensitivity and specificity and a high negative predictive value for evaluation of loco-regional involvement in follow-up of pediatric differentiated thyroid cancer. Diagnostic whole-body iodine scan is indicated when serum anti-thyroglobulin Ab is high, or in cases of discordant findings between US and stimulated thyroglobulin levels, or when stimulated thyroglobulin levels are >10 ng/ml (to evaluate for lung metastasis).

Autophagy in thyroid cancer: present knowledge and future perspectives

Thyroid cancer is the most common endocrine malignancy. Despite having a good prognosis in the majority of cases, when the tumor is dedifferentiated it does no longer respond to conventional treatment with radioactive iodine, the prognosis worsens significantly. Treatment options for advanced, dedifferentiated disease are limited and do not cure the disease. Autophagy, a process of self-digestion in which damaged molecules or organelles are degraded and recycled, has emerged as an important player in the pathogenesis of different diseases, including cancer. The role of autophagy in thyroid cancer pathogenesis is not yet elucidated. However, the available data indicate that autophagy is involved in several steps of thyroid tumor initiation and progression as well as in therapy resistance and therefore could be exploited for therapeutic applications. The present review summarizes the most recent data on the role of autophagy in the pathogenesis of thyroid cancer and we will provide a perspective on how this process can be targeted for potential therapeutic approaches and could be further explored in the context of multimodality treatment in cancer and personalized medicine.

Thyroglobulin as a biomarker of iodine deficiency: a review

BACKGROUND

Thyroglobulin, produced exclusively by the thyroid gland, has been proposed to be a more sensitive biomarker of iodine status than thyrotropin or the thyroid hormones triiodothyronine and thyroxine. However, evidence on the usefulness of thyroglobulin (Tg) to assess iodine status has not been extensively reviewed, particularly in pregnant women and adults.

SUMMARY

An electronic literature search was conducted using the Cochrane CENTRAL, Web of Science, PubMed, and Medline to locate relevant studies on Tg as a biomarker of iodine status. Since urinary iodine concentration (UIC) is the recommended method to assess iodine status in populations, only studies that clearly reported both Tg and UIC were included. For the purpose of this review, a median Tg <13 μg/L and a median UIC ≥100 μg/L (UIC ≥150 μg/L for pregnant women) were used to indicate adequate iodine status. We excluded studies conducted in subjects with either known thyroid disease or those with thyroglobulin antibodies. The search strategy and selection criteria yielded 34 articles of which nine were intervention studies. The majority of studies (six of eight) reported that iodine-deficient pregnant women had a median Tg ≥13 μg/L. However, large observational studies of pregnant women, including women with adequate and inadequate iodine status, as well as well-designed intervention trials that include both Tg and UIC, are needed. In adults, the results were equivocal because iodine-deficient adults were reported to have median Tg values of either <13 or ≥13 μg/L. Only studies in school-aged children showed that iodine-sufficient children typically had a median Tg <13 μg/L. Some of the inconsistent results may be partially explained by the use of different methodological assays and failure to assess assay accuracy using a certified reference material.

CONCLUSIONS

These data suggest that Tg does hold promise as a biomarker of iodine deficiency. However, it is associated with limitations. A median Tg cutoff of 13 μg/L warrants further investigation, particularly in adults or pregnant women, as there is a lack of both observational and intervention studies in these groups.

Assessment of iodine status in children, adults, pregnant women and lactating women in iodine-replete areas of China

BACKGROUND

Iodine deficiency disorders (IDD) are widespread in China. Presently, IDD have been put under control by Universal Salt Iodisation (USI) in China; however, there is a lack of evidence on whether the iodine status in adults, pregnant women and lactating women is optimal. This study was therefore conducted to assess the iodine nutrition and thyroid function of children, adults, pregnant women and lactating women residing in areas where the USI program is fully established.

DESIGN

Six areas were selected according to the geographical regions in China. In each of these areas, we selected 4 distinct groups of subjects (children, adults, pregnant women and lactating women) in regions where the coverage rate of iodised salt was more than 95% and the levels of iodine and fluoride in drinking water were less than or equal to 10 µg/L and 1 mg/L, respectively. We tested the iodine content of salt, urinary iodine (UI), free thyroxin (FT4), thyrotropin (TSH), thyroglobulin (Tg), thyroglobulin antibody (Tg-Ab) and antimicrosomal antibody (TM-Ab) in the 4 groups, and examined the thyroid volume in children.

RESULTS

The median urinary iodine (MUI) concentrations were 271.4 μg/L, 260.2 μg/L, 205.9 μg/L and 193.9 μg/L in children, adults, pregnant women and lactating women, respectively; MUI in children and adults were more than adequate. The goitre prevalence (GP) in children was 6.70%. The odds ratios (OR) of subclinical hypothyroidism in the Tg-Ab- or TM-Ab-positive groups were 3.80, 7.65, 2.01 and 7.47 for children, adults, pregnant women and lactating women, respectively, compared with the negative groups.

CONCLUSIONS

The iodine status in children and adults is above the requirement, we should reduce their iodine intake. Subclinical hypothyroidism easily occurs in the Tg-Ab or TM-Ab positive groups.

Vitamin D3 levels and insulin resistance in papillary thyroid cancer patients

Both insulin resistance (IR) and vitamin D deficiency (VDD) are found to be associated with many cancer types. In this study, we evaluated the presence of IR and VDD in thyroid cancer patients based on controls. Total 344 papillary thyroid cancer and 116 controls were part of the study. Glucose, insulin, homeostasis model analysis-insulin resistance (HOMA-IR) (control group 2.12 ± 0.9 and patient group 3.6 ± 1.1; p < 0.0001), LDL were significantly high; HOMA-S and vitamin D3 levels (control group 19.11 ± 8 and patient group 17 ± 16; p = 0.004) were significantly low in the patient group. Vitamin D deficiency (64/108 in controls vs 166/235; p = 0.026) and insulin resistance (24/108; 115/235; p < 0.0001) were more frequent in papillary thyroid cancer patients. After regression analysis, tumor diameter showed significant association with log-HOMA-IR (B = 0.315; p = 0.017) and log-vitamin D3 (B = 0.207; p = 0.04). Vitamin D deficiency and insulin resistance frequencies show no difference between micro- and macropapillary thyroid cancers. Receiver operating characteristic curve shows the best cutoff point for tumor diameter showing that the presence of lymph node metastasis was 0.65 cm with 81.2 % sensitivity and 52 % specificity. Best cutoff point for the capsular invasion tumor diameter was 0.75 cm with 83.3 % sensitivity and 60.4 % specificity. No difference between follicular and classical type papillary thyroid carcinomas has been yet discovered. As a result, thyroid cancer patients are more insulin resistant and vitamin D3 deficient. Vitamin D3 levels and HOMA-IR index may affect tumor diameter. Tumor size that is lower than 1 cm (0.65-0.75 cm) may be related with capsular invasion and lymph node involvement.

Utility of thyroglobulin measurements in fine-needle aspirates of space occupying lesions in the thyroid bed after thyroid cancer operations

BACKGROUND

Ultrasound, and sometimes cytology, cannot differentiate between recurrent or persistent thyroid cancer and benign forms of space occupying lesions (SOLs) in the thyroid bed, including unsuspected thyroid remnants, that are noted several months to years after thyroidectomy (Tx) for thyroid cancer. The purpose of the present study was to evaluate the hypothesis that measurement of thyroglobulin (Tg) in fine-needle aspirates from these lesions might help differentiate between benign and malignant SOLs in the thyroid bed.

METHODS

We studied 47 lesions in the thyroid bed from 43 patients who, 8-240 months previously, had 43 Txs for thyroid cancer. Eleven patients had a lobectomy and 32 patients had a total Tx. Also, some patients had radioactive iodine (RAI) ablation after their thyroid surgery and some did not. "Recurrence" was defined as the SOL, which was confirmed by cytological or histopathological results. "Benign SOL" was defined as a focal lesion, which was benign or nondiagnostic result on cytology and for which there was no RAI uptake on whole-body scintigraphy with both negative serum Tg and Tg antibodies. Diagnostic performances of fine-needle aspiration cytology (FNAC), FNA-Tg, and combining FNAC with FNA-Tg level were assessed for detection of malignant SOL. The diagnostic performance of FNA-Tg was assessed using three threshold values: 1 ng/mL, 10 ng/mL, and an FNA-Tg/serum-Tg ratio of 1.0.

RESULTS

FNA-Tg level and combining FNA-Tg levels with FNAC had higher sensitivities (100% in all three threshold values) and diagnostic accuracies (91.5%-95.7%) than FNAC alone (sensitivity of 85.3%, accuracy of 89.4%) in all threshold values. In both the RAI ablation and non-RAI ablation groups, the FNA-Tg levels and combining the FNA-Tg levels with FNAC had a higher sensitivity and diagnostic accuracy than FNAC alone with threshold values of 10 ng/mL and FNA-Tg/serum-Tg ratio of 1.0. The non-RAI ablation group did not have a different diagnostic accuracy than the RAI ablation group in all threshold values (p>0.05). FNA-Tg level showed a negative predictive value of 100% in all threshold values, in both the RAI ablation and the non-RAI ablation groups.

CONCLUSIONS

Measurement of Tg levels in the FNA of SOLs in the thyroid bed can be helpful in diagnosing tumor recurrence, because an FNA-Tg level lower than the threshold value has the added value of suggesting a benign lesion rather than tumor recurrence.

Thyroglobulin is a sensitive measure of both deficient and excess iodine intakes in children and indicates no adverse effects on thyroid function in the UIC range of 100-299 μg/L: a UNICEF/ICCIDD study group report

CONTEXT

The median urinary iodine concentration (UIC) is a biomarker of iodine intake. According to the World Health Organization, a median UIC in the range 100-199 μg/L indicates adequate and 200-299 μg/L more than adequate intake. Thyroglobulin (Tg) may be a promising functional biomarker of both iodine deficiency and excess.

OBJECTIVES

Using a standardized dried blood spots-Tg assay in children, we evaluated the Tg response to both low- and high-iodine intake and estimated the population cutoff point for iodine deficiency or excess. Also, we compared thyroid functions within the UIC ranges of 100-199 vs 200-299 μg/L.

DESIGN AND SETTING

We conducted a cross-sectional study in primary schools in 12 countries.

SUBJECTS

SUBJECTS were 6 to 12 years old (n = 2512).

MAIN OUTCOME MEASURES

We measured UIC, TSH, total T4, Tg, and thyroid antibodies.

RESULTS

Over a range of iodine intakes from severely deficient to excessive, Tg concentrations showed a clear U-shaped curve. Compared with iodine-sufficient children, there was a significantly higher prevalence of elevated Tg values in children with iodine deficiency (UIC <100 μg/L) and iodine excess (UIC >300 μg/L). There was no significant change in the prevalence of elevated Tg, TSH, T4, or thyroid antibodies comparing children within the UIC ranges of 100-199 vs 200-299 μg/L.

CONCLUSIONS

In school-aged children, 1) Tg is a sensitive indicator of both low and excess iodine intake; 2) a median Tg of <13 μg/L and/or <3% of Tg values >40 μg/L indicates iodine sufficiency in the population; 3) the acceptable range of median UIC in monitoring iodized salt programs could be widened to a single category of sufficient iodine intake from 100 to 299 μg/L.

Increasing the yield of recombinant thyroid-stimulating hormone-stimulated 2-(18-fluoride)-flu-2-deoxy-D-glucose positron emission tomography-CT in patients with differentiated thyroid carcinoma

OBJECTIVE

The aim of this study was to assess the accuracy of recombinant thyroid-stimulating hormone (rTSH)-stimulated 2-(18-fluoride)-flu-2-deoxy-D-glucose ((18)F-FDG) positron emission tomography (PET)-CT in detecting recurrence in patients with differentiated thyroid cancer.

METHODS

Consecutive (18)F-FDG PET-CT scans performed with rTSH stimulation between 2007 and 2010 in patients with a history of papillary or follicular thyroid carcinoma were reviewed. PET-CT findings were correlated with thyroglobulin levels, and histological, clinical and radiological follow-up.

RESULTS

58 rTSH PET-CT scans were performed in 47 patients with a previous thyroidectomy and radioiodine ablation. The only indication for PET-CT was a raised thyroglobulin level in 46 of 58 scans, with the remainder for characterisation of equivocal radiology or staging. 25 (43%) of PET-CT scans were positive for recurrent disease. Histological correlation was available for 21 (36%) scans. The overall sensitivity, specificity, positive predictive value and negative predictive value were 69%, 76%, 72% and 73%, respectively. Median unstimulated thyroglobulin in true-positive scans was 33 µg l(-1) and 2.2 µg l(-1) in the remainder (p=0.12). 4 of 35 (11%) patients with unstimulated thyroglobulin levels <10 µg l(-1) had true-positive scans. Median stimulated thyroglobulin in true-positive scans was 320 µg l(-1), and 10 µg l(-1) in the remainder (p=0.046), with no positive scans with a stimulated thyroglobulin <8 µg l(-1). PET-CT directly influenced patient management in 17/58 (29%) scans.

CONCLUSION

rTSH PET-CT is a useful imaging technique for detecting disease recurrence in patients with iodine-resistant differentiated thyroid cancer. Low stimulated thyroglobulin levels are potentially useful in identifying patients unlikely to benefit from a PET-CT scan.

Management of thyroid cancers

Thyroid cancers cover a large spectrum of disease with diametrically opposite prognosis. At one end of the spectrum we have the well differentiated cancers which carry an excellent prognosis, while at the other end there is anaplastic cancer with high mortality rates and dismal prognosis. Management of thyroid cancers still has some controversial issues due to lack of randomized controlled trials. Extent of surgery, extent of neck dissection, role of radioiodine treatment and thyroid stimulating hormone suppression are still debatable. In this review, we highlight these controversial issues and give guidelines for the management and follow up of patients with thyroid cancer.

Thyroglobulin measurement in fine-needle aspirate washouts: the criteria for neck node dissection for patients with thyroid cancer

BACKGROUND

Several studies report that detection of thyroglobulin (Tg) in fine-needle aspiration (FNA) biopsy washout fluid from lymph nodes identifies recurrences/metastases of differentiated papillary thyroid cancer (DPTC) in the neck with higher sensitivity and specificity than fine-needle aspiration cytology (FNAC). However, the diagnostic FNA-Tg cutoff values have not yet been established.

OBJECTIVE

To determine an appropriate diagnostic threshold value for Tg levels in FNA washout fluid in patients with neck node metastases or recurrences of DPTC.

DESIGN

We performed ultrasound (US)-guided FNAC and measured Tg levels in FNA washout fluid (FNA-Tg). Final diagnoses were confirmed by histological examination of excised specimens or by follow-up examinations for at least 24 months.

PATIENTS

A total of 168 ultrasonographically detected lymph nodes from 168 patients with DPTC were included.

MEASUREMENTS

In comparison with FNAC, we evaluated diagnostic sensitivity, specificity and accuracy of metastasis detection according to several predetermined threshold levels: 1, 10, 100 ng/ml, mean+2SD of node-negative patients, and FNA-Tg/serum-Tg > 1.

RESULTS

The diagnostic sensitivity was lowest at 77.3% for FNAC alone. The lower FNA-Tg threshold levels showed higher diagnostic sensitivity whereas the higher FNA-Tg showed higher specificity. In addition to the FNAC results, FNA-Tg levels showed 95.0% sensitivity, 81.6% specificity, 92.6% in positive predictive value (PPV) and 87.0% in negative predictive value (NPV) with the threshold of FNA-Tg level at 10 ng/ml, serum-Tg or mean+2SD of FNA-Tg measured in node-negative patients. The diagnostic accuracy of FNA-Tg was higher in neck node recurrences after thyroid surgery than in the metastasis of patients waiting for surgery.

CONCLUSION

FNA-Tg measurement as well as FNAC should be performed either before or after surgery to evaluate neck node metastases or recurrences in patients with differentiated thyroid carcinomas. We recommend that the threshold values for FNA-Tg levels should be > 10 ng/ml if the serum-Tg level or the mean+2SD in node-negative patients is not available for reference.

Thyroglobulin measurement in differentiated thyroid carcinoma management

Differentiated thyroid cancer (DTC) is a rare disease with a generally good prognosis. The initial treatment is total thyroidectomy with ablation of thyroid remnants by iodine-131 (¹³¹I). Currently, serum thyroglobulin (Tg) measurement and neck high-resolution ultrasound are the basis of follow-up. The thyroid cells are the only source of Tg in the human body, therefore, the presence of Tg after total thyroidectomy and ablative ¹³¹I therapy indicates persistence or recurrence of DTC. The sensitivity of Tg measurements can be optimized by clinical and technical improvements. Clinically, measurements of thyroid-stimulating hormone (TSH)-stimulated Tg after thyroid hormone withdrawal, or exogenous TSH administration in patients with undetectable serum Tg during thyroid hormone-suppression therapy, is recommended for revealing occult disease. Technically, the development of Tg assays with improved functional sensitivity enhances the value of Tg measurements, allowing us to measure Tg without any TSH stimulation during DTC with high negative predictive value. In particular, increasing serum Tg concentrations in highly sensitive assays are early and reliable indicators of recurrent disease. Several imaging methods are available for the localization of recurrences and metastases (i.e., ¹³¹I whole-body scan for iodine-positive metastases and fluorodeoxyglucose-PET or PET/CT scans for iodine-negative ones), but their rational use should be dictated by Tg testing results. This will be realized in a limited follow-up protocol, warranting the detection of recurrences of DTC and reducing patient burden and medical costs.

Routine 201Tl scintigraphy in the follow-up of patients with differentiated thyroid carcinoma: diagnostic accuracy and clinical impact

OBJECTIVE

The use of 201Tl scintigraphy as a routine imaging modality in the follow-up of patients with differentiated thyroid carcinoma (DTC) is controversial. The purpose of this retrospective study was to evaluate the diagnostic accuracy and clinical impact of routine 201Tl scintigraphy in the follow-up of patients with DTC.

MATERIALS AND METHODS

Three hundred and twenty-one patients (261 women, 60 men) with DTC (243 papillary thyroid carcinomas, 78 follicular thyroid carcinomas) were enrolled in this study. Two hundred and seventy-six patients underwent total or near total thyroidectomy (group 1) and 45 patients underwent subtotal thyroidectomy or unilateral lobectomy (group 2). A total of 1523 201Tl scintigraphy examinations were performed between 1987 and 2003. The duration of follow-up ranged from 13 to 204 months. 201Tl scintigraphy was performed 10 and 60 min after intravenous administration of 74 MBq 201Tl chloride.

RESULTS

In group 1, 55 recurrent lesions were confirmed in 39 patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 71.8%, 98.3%, 87.5%, 95.5% and 94.6%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy were 63.6%, 99.7%, 89.7%, 98.5% and 98.3%, respectively. Of the 35 thallium-positive recurrent lesions, 21 (60%) were removed by surgery and seven (20%) were treated with external-beam radiation therapy. All the thallium-negative recurrent lesions were treated with 131I therapy. The difference between the management of thallium-positive and thallium-negative recurrences was statistically significant (P<0.001). In group 2, 10 recurrent lesions were confirmed in seven patients. In a patient-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy for detecting recurrent DTC were 85.7%, 94.7%, 75%, 97.3% and 93.3%, respectively. In a lesion-based analysis, the sensitivity, specificity, positive and negative predictive values, and accuracy of 201Tl scintigraphy was 80%, 97.5%, 80%, 97.5% and 95.6%, respectively. All of the seven patients were treated with completion of total thyroidectomy and subsequent 131I ablation therapy.

CONCLUSIONS

201Tl scintigraphy was not a highly sensitive imaging modality in routine follow-up of patients with DTC after total thyroidectomy. However, it had a clinical impact on the choice of optimal therapeutic approaches. In the follow-up of patients who underwent partial thyroidectomy, 201Tl scintigraphy was useful in the detection of recurrent DTC.

Preoperative undetectable serum thyroglobulin in differentiated thyroid carcinoma: incidence, causes and management strategy

BACKGROUND

In recent years serum thyroglobulin (Tg) measurement during thyroxine (T4) treatment and/or after stimulation by endogenous TSH or recombinant human TSH (rhTSH) has eclipsed other diagnostic procedures in managing patients with differentiated thyroid cancer (DTC). However, preoperative undetectable Tg was reported in up to 12% of patients affected by DTC and recurrences of DTC with no increase in serum Tg have also been described. Clearly, a negative Tg measurement may falsely reassure both the patient and the clinician in these cases.

AIM

We retrospectively evaluated the incidence of undetectable or reduced preoperative serum Tg in a group of 436 patients affected by DTC. Additionally, we evaluated the role of Tg retesting by two different immunoassays in patients with low Tg at first measurement.

METHODS

We retrospectively selected 17 patients with undetectable (i.e. less than functional sensitivity of assay method) or reduced Tg (i.e. between functional sensitivity and minimum normal value) among 436 patients with histologically proved DTC. The remaining 419 patients were used as control cases. Frozen sera from all patients were retested by two different Tg immunoassays.

RESULTS

Globally, 17 out of 436 (3.8%) patients showed undetectable (n = 5, 1.1%) or reduced (n = 12, 2.7%) preoperative Tg. The Tg level was above the minimum normal value in 3 and 4 out of 5, and 8 and 9 out of 12 of these patients, respectively, when two different immunoassays were employed. On the other hand, undetectable or reduced Tg levels were found in 3.0%-5.1% of control cases when different immunoassays were used.

CONCLUSIONS

Regardless of the method employed, 3.0-5.1% of patients with DTC showed undetectable or reduced preoperative Tg. This fact must be recognized, as Tg cannot be used as a benchmark for DTC follow-up in these cases. However, Tg retesting with different immunoassays seems to be useful in ruling out these pitfalls in a large majority of patients, and also indicates the most effective assay to be employed in these cases.

Possible reasons for different pattern disappearance of thyroglobulin and thyroid peroxidase autoantibodies in patients with differentiated thyroid carcinoma following total thyroidectomy and iodine-131 ablation

The purpose of this study was to reveal some possible factors for the differences between the pattern of disappearance of thyroglobulin autoantibodies (anti-Tg) and thyroid peroxidase autoantibodies (anti-TPO) in patients with differentiated thyroid carcinoma following thyroidectomy and iodine-131 ablation. Patients with a history of follicular cell derived cancer (papillary, follicular, both papillary and follicular, Hürthle cell) and high pre-operative titers of anti-TPO and/or anti-Tg autoantibodies were retrospectively studied. Thyroglobulin (Tg) levels were measured using radio-immunometric assay (RIA). Anti-Tg and anti-TPO levels during the first 6 yr' follow-up were measured by passive agglutination, during the following 10 yr by ELISA method and during the last 2 yr by chemiluminescence assay. A statistically significant difference was observed between median time (72 months) of disappearance of anti-TPO and median time (39 months) of disappearance of anti-Tg in patients with complete ablation of thyroid tissue, following iodine-131 administration (p=0.0395, Logrank statistic=4.24, Kaplan-Meier method). A statistically significant difference was observed between median time (106 months) of disappearance of anti-TPO and median time (33 months) of disappearance of anti-Tg in patients >45 yr of age (p=0.034) and between median time (111 months) of disappearance of anti-TPO and median time (41 months) of disappearance of anti-Tg in patients with tumor size <2 cm (p=0.0175). We concluded that patients with differentiated thyroid carcinoma and pre-surgical elevated titers of both Tg and anti-TPO tend to become earlier anti-Tg seronegative. Although tumor size and age may influence the pattern of thyroid autoantibody reduction, the exact reasons for the different rhythm of autoantibodies decrease must further be evaluated.

Assessment of iodine status using dried blood spot thyroglobulin: development of reference material and establishment of an international reference range in iodine-sufficient children

CONTEXT

Thyroglobulin (Tg) may be a valuable indicator of improving thyroid function in children after salt iodization. A recently developed Tg assay for use on dried whole blood spots (DBS) makes sampling practical, even in remote areas.

OBJECTIVE

The study aim was to develop a reference standard for DBS-Tg, establish an international reference range for DBS-Tg in iodine-sufficient children, and test the standardized DBS-Tg assay in an intervention trial.

DESIGN, PARTICIPANTS, AND INTERVENTIONS

Serum Tg reference material of the European Community Bureau of Reference (CRM-457) was adapted for DBS and its stability tested over 1 yr. DBS-Tg was determined in an international sample of 5- to 14-yr-old children (n = 700) who were euthyroid, anti-Tg antibody negative, and residing in areas of long-term iodine sufficiency. In a 10-month trial in iodine-deficient children, DBS-Tg and other indicators of iodine status were measured before and after introduction of iodized salt.

RESULTS

Stability of the CRM-457 Tg reference standard on DBS over 1 yr of storage at -20 and -50 C was acceptable. In the international sample of children, the third and 97th percentiles of DBS-Tg were 4 and 40 microg/liter, respectively. In the intervention, before introduction of iodized salt, median DBS-Tg was 49 microg/liter, and more than two thirds of children had DBS-Tg values greater than 40 microg/liter. After 5 and 10 months of iodized salt use, median DBS-Tg decreased to 13 and 8 microg/liter, respectively, and only 7 and 3% of children, respectively, had values greater than 40 microg/liter. DBS-Tg correlated well at baseline and 5 months with urinary iodine and thyroid volume.

CONCLUSIONS

The availability of reference material and an international reference range facilitates the use of DBS-Tg for monitoring of iodine nutrition in school-age children.

Follicular and Hürthle cell carcinoma of the thyroid gland

Follicular and Hürthle cell carcinoma of the thyroid gland are uncommon tumors that are genotypically similar. Current and future diagnostic adjuncts, treatment, and postoperative follow-up for patients with follicular and Hürthle cell cancer are outlined. Risk factors for recurrence and mortality and the reported outcomes of treatment of follicular and Hürthle cell carcinoma are reviewed.

Serum thyroglobulin measurement: clinical background and main methodological aspects with clinical impact

It is worldwide recognized that circulating thyroglobulin (Tg) measurement represents a fundamental tool in the follow-up of patients affected by differentiated thyroid cancer (DTC). In the last American and European Consensus Conferences, a surveillance guideline has been extended to the use of thyrotropin (TSH)-stimulated Tg levels for thyroidectomized patients without clinical evidence of residual tumor with Tg below 1 microg/l during TSH suppression. Therefore, sensitivity of the methods is critical to detect small amounts of Tg and/or to observe minimal changes in Tg concentration in the management of DTC patients. It has been proposed that only methods providing the greatest distinction between the lower limit of euthyroid reference range (approximately 3.0 microg/l) and the functional sensitivity limit (at least 1 microg/l) of the assay may offer a suitable clinical sensitivity for detecting small amounts of functioning thyroid tissue in TSH-suppressed state (1 g of normal thyroid tissue results in a serum Tg of approximately 1 microg/l when TSH is normal and about 0.5 microg/l when TSH is suppressed). In the last 30 years sensitivity of Tg measurements has been greatly improved, nowadays methods can achieve very good analytical and functional sensitivity to give reliable results also in the very low concentration range (between 0.1 and 1 microg/l). In addition, with the introduction of fully automated assays, results can be readily available to the clinician while patients are still in the ambulatory area. However, despite the large clinical use of Tg measurement, wide differences (by threefold) still remain between results produced in different laboratories due to poor standardization, heterogeneity of circulating Tg, interference from auto-antibodies, differences in the epitope recognition by antibodies used in the assays.

Diagnostic molecular markers in thyroid cancer

The use of molecular assays to analyze clinical tissues in the diagnosis and management of thyroid cancer, similar to other tumors, will likely allow for more accurate characterization of the aggressiveness of individual tumors and may allow for the early diagnosis of recurrence. The application of these methods to thyroid nodules and nodal metastases is less encumbered by difficulties arising from amplification of transcripts in non-thyroid cells. For these tissues, these assays are likely to be used clinically in the near-future. New data arising from cDNA arrays identifying novel markers of malignancy or tumor aggressiveness make this a growing area of interest. The use of molecular assays in diagnosing distant metastases is more problematic due to issues with ectopic expression of either full length or splice variants of genes thought to be thyroid-specific. Assay quantitation is a complex problem owing to variability in the level of expression of "housekeeping" genes and the variety of phlebotomy and RT-PCR methods reported. Additional research in this area is clearly required before a recommendation can be given regarding clinically applicability of these tests.

Long-Term Follow-Up of a Patient With Papillary Thyroid Carcinoma, Elevated Thyroglobulin Levels, and Negative Imaging Studies

OBJECTIVE

To describe a patient with papillary thyroid carcinoma who had measurable thyroglobulin (Tg) levels for 20 years without clinical or imaging evidence of a malignant lesion.

METHODS

We reviewed the clinical course, pathologic findings, Tg measurements, and results of various imaging studies in our patient and reviewed the literature regarding Tg-positive, diagnostic total-body radioiodine scan-negative patients with thyroid cancer.

RESULTS

Four months after a 3.5- by 3.5-cm follicular thyroid cancer was removed from the anterior neck area of a 5-year-old girl, a bilateral subtotal thyroidectomy was performed. At age 12 years, she presented with a 2-cm mass on the right side of the neck. After a completion thyroidectomy, recurrent mixed papillary-follicular thyroid cancer was found scattered throughout the remaining thyroid parenchyma. Although a postoperative diagnostic total-body radioiodine scan did not reveal uptake of (131)I, the Tg level was 58 ng/mL. Despite Tg levels as high as 2,528 ng/mL, the patient had no clinical evidence of thyroid cancer during a 20-year period of follow-up. Moreover, numerous imaging studies, including total-body scanning after the administration of 150 mCi of (131)I and [(18)F]fluorodeoxyglucose positron emission tomography, were negative. Review of pathologic specimens from both operations with use of updated diagnostic criteria indicated that the tumor was a papillary thyroid carcinoma.

CONCLUSION

Our observations and the observations of other investigators indicate that some thyroid cancers produce Tg so efficiently that high levels of Tg may be associated with tumors that remain too small to be detected by imaging studies. The Tg levels may remain stable, decline, or even disappear over time without treatment.

Thyroglobulin assay 4 weeks after thyroidectomy predicts outcome in low-risk papillary thyroid carcinoma

Background: Thyroidectomy followed by administration of large activities of

Factors influencing the basal and recombinant human thyrotropin-stimulated serum thyroglobulin in patients with metastatic thyroid carcinoma

The serum thyroglobulin (Tg) level is the most sensitive marker for detecting residual thyroid carcinoma. We hypothesized that the basal and TSH-stimulated Tg levels in patients with metastatic thyroid carcinoma would reflect tumor volume, histological subtype, and location of metastatic lesions. A retrospective review of 417 thyroid cancer survivors undergoing evaluation for residual disease with the assistance of recombinant human TSH (rhTSH) was performed. In 169 patients with metastatic disease, we found that the basal Tg level directly correlated with the number of lesions, and that it was highest in patients with follicular and lowest in those with papillary thyroid carcinoma. The basal Tg level was highest in patients with bone metastases and lowest in those with cervical metastases. The fold increase in the serum Tg after rhTSH treatment was highest in papillary thyroid carcinoma and lowest in Hurthle cell carcinoma. The fold increase in Tg was not influenced by tumor volume or by the site of metastatic lesions. Multivariate analysis showed multiple interactions between factors, but did not identify one factor that significantly influenced basal Tg or fold increase. We conclude that the location and volume of metastases influence basal Tg, but not its responsiveness to rhTSH, whereas the histological type of carcinoma influences both basal Tg and responsiveness to rhTSH.

Thyroglobulin: a specific serum marker for the management of thyroid carcinoma

Thyroglobulin measurements in tissue and serum play an integral role in the evaluation of patients who have thyroid cancer. Immunohistochemical detection of thyroglobulin in surgical specimens is useful in the differential diagnosis of tumors of unknown origin; however, the most important application of thyroglobulin measurement in clinical practice is in the postsurgical management of differentiated thyroid cancer. Serum thyroglobulin is a highly specific and sensitive tumor marker for detecting persistent or recurrent thyroid cancer and for monitoring clinical status. The reappearance of circulating thyroglobulin after total thyroid ablation is pathognomonic for the presence of tumor. The measurement of thyroglobulin in serum is challenging, however, and several analytical problems limit assay performance. Thyroglobulin autoantibody interference is a particularly significant concern that requires all thyroglobulin samples to be screened for their presence. No immunoassay is totally free from interference by thyroglobulin autoantibodies. Measurement of thyroglobulin mRNA to detect circulating tumor cells may help to overcome some of the limitations of current protein-detection methods; serum thyroglobulin will continue to remain the "gold standard." The complex functional features of thyroid carcinomas make sole reliance upon any one diagnostic technique, including thyroglobulin assessments, potentially misleading. Thyroglobulin measurements are a critical component of a multifaceted diagnostic approach to this disease.

Reversible Renal Insufficiency Attributable to Thyroid Hormone Withdrawal in a Patient With Type 2 Diabetes Mellitus

OBJECTIVE

To present a case of papillary thyroid carcinoma and the need for follow-up surveillance in a patient with type 2 diabetes mellitus who was being treated with metformin.

METHODS

The clinical and laboratory findings are summarized, and results of whole-body scanning are described. A discussion addresses the importance of monitoring renal function during thyroid hormone withdrawal for scintigraphic imaging with use of radioactive iodine.

RESULTS

A 60-year-old man with type 2 diabetes was diagnosed with metastatic papillary thyroid carcinoma, and renal insufficiency developed during withdrawal from thyroid hormone for surveillance 131 I whole-body scanning. An increase in thyroglobulin attributable to recombinant human thyrotropin stimulation led to detection of persistent cancer, and thyroid hormone withdrawal was begun in preparation for further 131 I treatment. Pretherapy laboratory results revealed a thyrotropin level of 46.1 mIU/mL, a thyroglobulin level of 13.7 ng/mL, and an increased serum creatinine (Cr) concentration from a baseline of 0.9 mg/dL to 1.9 mg/dL while the creatinine clearance (CrCl) was 67 mL/min. Therapy with metformin was immediately discontinued. On the basis of results from 131 I whole-body dosimetry, the patient was treated with 250 mCi of 131 I. Levothyroxine therapy was resumed approximately 72 hours after 131 I therapy, and blood tests 2 weeks thereafter revealed a Cr of 1.1 mg/dL and a CrCl of 105 mL/min. The metformin treatment was then reinitiated without any complications.

CONCLUSION

Patients with hypothyroidism can have up to a 20 to 30% decrease in glomerular filtration rate, which tends to resolve when euthyroidism is achieved. In patients with diabetes taking metformin who have hypothyroidism for any reason including thyroid hormone withdrawal, serum Cr levels should be monitored until thyroid hormone levels normalize. Metformin therapy should be discontinued in patients with significant renal impairment, defined as either a serum Cr level of 1.5 mg/dL or more in men and 1.4 mg/dL or more in women or a CrCl of less than 60 mL/min.

Prognostic value of thyroglobulin serum levels and 131I whole-body scan after initial treatment of low-risk differentiated thyroid cancer

Diagnostic iodine-131 whole-body scan ((131)I-WBS) and serum thyroglobulin values (Tg) performed 6 to 12 months after thyroid ablation for differentiated thyroid carcinoma were evaluated in 194 consecutive patients at the Hospital de Navarra, (Pamplona, Spain). All patients underwent near-total thyroidectomy and (131)I ablation with 3.7 GBq. Patients with positive anti-Tg antibodies or with (131)I uptake outside the neck were previously excluded. Uptake of (131)I in the thyroid bed was detected in 27 patients (13.9%). Serum Tg levels were below 0.5 ng/mL in 133 patients, ranged from 0.5-10 ng/mL in 39 patients, and was above 10 ng/mL in 22 patients. After a follow-up of 7.7 +/- 3.3 years, persistence of the illness has been observed in 2 patients with undetectable Tg (1.5%), but metastases were not detected in any case. In those with Tg higher than 0.5 ng/mL, 29 of 61 patients had persistence of the disease (47.5%) with evidence of metastases in 15 (24.5%), irrespective of the initial total body scan (131)I uptake. In conclusion, serum Tg levels obtained after thyroid ablation has a good prognostic value and permits the selection of patients for further diagnostic studies, while diagnostic (131)I-WBS performed at that time did not correlate with results of Tg and scarcely provides additional information.

6: Thyroid nodules and thyroid cancer

Thyroid nodules are common clinically (prevalence, about 5%) and even more common on ultrasound examination (about 25%). About 5% of thyroid nodules are malignant. Most thyroid cancers are well-differentiated papillary or follicular tumours with an excellent prognosis (10-year survival, 80%-95%). The incidence of papillary thyroid cancer appears to be increasing on the east coast of Australia. Fine-needle aspiration biopsy of the thyroid is the most cost-effective diagnostic tool. Recommended initial management of all follicular carcinomas and of papillary carcinomas > 1.0 cm is total thyroidectomy followed by radioiodine ablation. Most patients should be managed postoperatively with doses of thyroid hormone sufficient to suppress plasma levels of thyroid-stimulating hormone. Recurrences can occur many years after initial therapy, and follow-up should be lifelong. Thyroid nodules are very common, but have a relatively low risk of malignancy

Discordant serum thyroglobulin results generated by two classes of assay in patients with thyroid carcinoma: correlation with clinical outcome after 3 years of follow-up

BACKGROUND

Serum thyroglobulin measurement is an integral part of monitoring patients with thyroid carcinoma, but analytic problems pose serious difficulties in the utility of this test.

METHODS

Between 1997 and 1998, serum samples from 83 patients with differentiated thyroid carcinoma were collected. Serum thyroglobulin was assayed by both radioimmunoassay and by an immunoradiometric assay. The disease status of patients with discordant serum thyroglobulin results was assessed in June 2001. Therefore, the predictive value of a single thyroglobulin measurement was assessed by evaluating the clinical status of patients 3 years later.

RESULTS

Discordant serum thyroglobulin results were noted in 17 (20.4%) patients. Of the 17 patients with discordant results, 16 had adequate clinical follow-up data. Of these 16 patients, 11 patients had detectable levels of serum thyroglobulin by immunoradiometric assay (range, 1.4-350 microg/L) whereas levels were undetectable by radioimmunoassay (< 1 microg/L). All 11 patients had evidence of metastases 3 years later. Two patients had undetectable serum thyroglobulin levels using the immunoradiometric assay (< 1 microg/L), whereas they had detectable levels using radioimmunoassay (serum thyroglobulin 7.2-30 microg/L). The serum samples from both patients had normal recoveries and positive antithyroglobulin antibodies. Both patients developed metastases 3 years later.

CONCLUSIONS

False-negative serum thyroglobulin results were significantly higher with the radioimmunoassay method compared with the immunoradiometric assay. The immunoradiometric assay is more reliable than the radioimmunoassay, particularly in patients who have no thyroglobulin antibodies. This finding is novel in that traditional immunoradiometric assay systems compared with radioimmunoassays usually have a higher incidence of false-negative results when assessed against clinical status. The immunoradiometric assay is subject to false-negative results in some patients with thyroglobulin antibodies, even when recovery experiments indicate the absence of interference. Thyroglobulin antibodies should be measured in all patients with differentiated thyroid carcinoma and if positive, results should be interpreted with extreme caution.

Development of a dried whole-blood spot thyroglobulin assay and its evaluation as an indicator of thyroid status in goitrous children receiving iodized salt

BACKGROUND

Serum thyroglobulin appears to be a sensitive marker of thyroid dysfunction in endemic goiter. However, its value as an indicator of thyroid status in children after the introduction of iodized salt has not been tested.

OBJECTIVE

The objective was to optimize and validate a thyroglobulin assay on dried whole blood spots and to evaluate thyroglobulin as an indicator of thyroid response to iodized salt.

DESIGN

A standardized, commercially available, sandwich fluoroimmunometric serum thyroglobulin assay was adapted for use on blood spots and validated in Swiss children. In a 1-y prospective study in 377 goitrous Moroccan children aged 6-15 y, the assay was used to measure thyroglobulin before and after the introduction of iodized salt. Urinary iodine, thyroid volume, thyrotropin, and thyroxine were measured, and regression was done with thyroglobulin as the dependent variable.

RESULTS

Correlation between the blood spot and serum assays was excellent (r = 0.98). The SD of the difference between the blood spot and serum assays was 3.8 micro g/L; the median CVs for the blood spot assay in controls and samples were 6.3% and 14.4%, respectively. Median thyroglobulin was 24.5 (range: 0-328.8) micro g/L at baseline and fell significantly after the introduction of iodized salt to 6.2 (0-83.1) and 4.4 (0-47.1) micro g/L at 5 and 12 mo, respectively (P < 0.0001). Regression of urinary iodine and thyroid volume on thyroglobulin was highly significant at baseline and at 5 mo (P < 0.001).

CONCLUSION

Thyroglobulin, measured in dried whole blood spots, may be a valuable indicator of improving thyroid function in children after supplementation with iodized salt.

Effects of therapeutic doses of 131I in thyroid papillary carcinoma patients with elevated thyroglobulin level and negative 131I whole-body scan: comparative study

OBJECTIVE

Previous studies have shown a high rate of visualization of uptake and a decrease in serum thyroglobulin (Tg) after therapeutic doses of 131I in well-differentiated thyroid cancer patients with elevated thyroglobulinaemia but negative diagnostic 131I whole-body scan (DxWBS), but its therapeutic effect remains controversial. We evaluate the effect of therapeutic doses of 131I in patients with elevated thyroglobulin level but negative DxWBS.

DESIGN

Among papillary thyroid carcinoma patients who underwent total or near-total thyroidectomy and remnant ablation with radioiodine during 1996 to 2000 in our hospital, the patients who showed elevated serum Tg levels and no abnormal uptake in DxWBS were selected. The selection for treatment or no treatment was decided according to the preference of the patients, considering side-effects of therapeutic doses of 131I, and the patients were thereafter studied retrospectively.

PATIENTS

Sixty papillary thyroid carcinoma patients with elevated thyroglobulinaemia but negative DxWBS were included. Twenty-eight patients were treated, and 32 were untreated.

MEASUREMENTS

We compared serum Tg levels measured at less than 3 months before the administration of therapeutic doses of 131I or DxWBS with the levels at 6-12 months after administration between two groups. Comparable data on changes in serum Tg levels during TSH suppression (Tg-on) and those in hypothyroid phase (Tg-off) were available in 25 and 49 patients, respectively.

RESULTS

Percentage decreases in both Tg-on and Tg-off levels of the treated group [41.2 (10.1-94.1)% and 37.0 (-176.6-88.4)%, respectively] were significantly higher than those of the untreated group [-43.6 (-180.1-7.3)% and -66.6 (-10644.2-39.1)%, respectively] (P < 0.001). The treated patients were followed-up for 23.8 +/- 19.6 months after the administration of therapeutic doses of 131I. In four cases, serum Tg levels converted to negative (< 1.0 ng/ml) both on and off T4 15-22 months after the administration of therapeutic doses of 131I, and negative serum Tg levels persisted for 24-70 months. However, negative conversion of elevated serum Tg levels was not observed in any of the untreated group. Post-treatment WBS revealed pathologic uptake in 12 of 28 cases (42.9%).

CONCLUSIONS

This study revealed that the administration of therapeutic doses of 131I has a therapeutic effect, at least for palliation in short-term observation, considering the serum Tg level as an index of tumour burden, and that it can disclose previously undiagnosed lesion in some patients with differentiated thyroid cancer who show elevated thyroglobulin level but negative diagnostic 131I whole-body scan.

A consensus report of the role of serum thyroglobulin as a monitoring method for low-risk patients with papillary thyroid carcinoma

Recent studies have provided new information regarding the optimal surveillance protocols for low-risk patients with differentiated thyroid cancer (DTC). This article summarizes the main issues brought out in a consensus conference of thyroid cancer specialists who analyzed and discussed this new data. There is growing recognition of the value of serum thyroglobulin (Tg) as part of routine surveillance. An undetectable serum Tg measured during thyroid hormone suppression of TSH (THST) is often misleading. Eight studies show that 21% of 784 patients who had no clinical evidence of tumor with baseline serum Tg levels usually below 1 micro g/liter during THST had, in response to recombinant human TSH (rhTSH), a rise in serum Tg to more than 2 micro g/liter. When this happened, 36% of the patients were found to have metastases (36% at distant sites) that were identified in 91% by an rhTSH-stimulated Tg above 2 micro g/liter. Diagnostic whole body scanning, after either rhTSH or thyroid hormone withdrawal, identified only 19% of the cases of metastases. Ten studies comprising 1599 patients demonstrate that a TSH-stimulated Tg test using a Tg cutoff of 2 micro g/liter (either after thyroid hormone withdrawal or 72 h after rhTSH) is sufficiently sensitive to be used as the principal test in the follow-up management of low-risk patients with DTC and that the routine use of diagnostic whole body scanning in follow-up should be discouraged. On the basis of the foregoing, we propose a surveillance guideline using TSH-stimulated Tg levels for patients who have undergone total or near-total thyroidectomy and (131)I ablation for DTC and have no clinical evidence of residual tumor with a serum Tg below 1 micro g/liter during THST.

Evaluation of a thyroid nodule

Solitary thyroid nodules are common entities and the majority of these are benign. The main goal in evaluating these nodules is to identify the [figure: see text] nodules with malignant potentials. A multitude of diagnostic tests is available to the clinician. FNA biopsy is now considered the gold standard diagnostic test in the evaluation of a thyroid nodule. Ultrasound and nuclear scans are also useful tests, but are best used in conjunction with FNA. Clinical decisions are often based on the results of the FNA. A diagram of the clinical decision process based on FNA findings is presented in Fig. 1. Despite the clinical advantages that are provided by the FNA results, the clinician should not dismiss the importance of other clinical prognostic indicators to optimize timely treatment.

Inflammatory thyroid disorders

Inflammatory thyroid disorders encompass a broad spectrum of diseases that are generally self-limited, and relatively easy to diagnose and manage. Autoimmune subtypes are by far the most commonly encountered diagnoses and create the most confusion because of simultaneous overlap and the potential for interconversion among the subtypes. The otolaryngologist will frequently see these disorders and provide valued consultative care and surgical intervention as needed.