Clinical diagnosis of Graves' or non-Graves' hyperthyroidism compared to TSH receptor antibody test

Clinical characteristics and outcomes of patients with TSH-secreting pituitary adenoma and Graves' disease - a case report and systematic review

BACKGROUND

Coexistence of TSH-secreting pituitary adenoma (TSHoma) and Graves' disease (GD) is rare and complicates the management decision.

METHODS

We present a case of the co-existence of TSHoma and GD. In addition, we systematically searched articles describing TSHoma and GD in the same patient published until 20th March 2023, using Pubmed, Scopus and Embase.

CASE PRESENTATION

A 46-year-old man presented with symptoms of thyrotoxicosis. His thyroid function tests showed serum TSH 3.35 (reference range 0.3-4.2) mIU/L, FT3 19.7 (3.7-6.4) pmol/L, and FT4 68.9 (11-23.3) pmol/L. The serum TSH receptor antibody was 11.5 mIU/L (positive at ≥ 1.75 mIU/L). Pituitary magnetic resonance imaging showed macroadenoma compressing the optic chiasm. The patient underwent trans-sphenoidal resection of pituitary adenoma. Postoperatively, he remained on maintenance carbimazole and octreotide.

RESULTS

Fourteen articles comprising 15 patients were identified from the systemic search. A total of 16 patients (including the current case) were included in the systematic review. The mean (± SD) age at diagnosis was 41 ± 13.6 years. The majority were females (75%). The median (IQR) TSH was 1.95 (0.12-5.5) mIU/L, the median (IQR) free T3 was 11.7 (7.6-19.7) pmol/L and the median (IQR) free T4 level was 47.6 (33.3-64.4) pmol/L. Ten (76.9%) patients had positive TSH receptor antibody levels. 84.6% had pituitary macroadenoma. Pituitary surgery was performed in 12 (75%) patients. At the last follow-up, 4 (25%) patients had complete resolution of symptoms after pituitary surgery, 3 (18.7%) were on maintenance treatment with thionamides for GD, 1 (6.25%) on beta-blockers and 1 (6.25%) on somatostatin analog.

CONCLUSION

TSHoma and GD can co-exist, and it is essential to identify this rare association as it can significantly impact treatment strategies.

The Use of Tissue-on-Chip Technology to Focus the Search for Extracellular Vesicle miRNA Biomarkers in Thyroid Disease

Small extracellular vesicles (sEVs) contain microRNAs (miRNAs) which have potential to act as disease-specific biomarkers. The current study uses an established method to maintain human thyroid tissue ex vivo on a tissue-on-chip device, allowing the collection, isolation and interrogation of the sEVs released directly from thyroid tissue. sEVs were analysed for differences in miRNA levels released from benign thyroid tissue, Graves' disease tissue and papillary thyroid cancer (PTC), using miRNA sequencing and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) to identify potential biomarkers of disease. Thyroid biopsies from patients with benign tissue (n = 5), Graves' disease (n = 5) and PTC (n = 5) were perfused with medium containing sEV-depleted serum for 6 days on the tissue-on-chip device. During incubation, the effluents were collected and ultracentrifuged to isolate sEVs; miRNA was extracted and sequenced (miRNASeq). Out of the 15 samples, 14 passed the quality control and miRNASeq analysis detected significantly higher expression of miR-375-3p, miR-7-5p, miR-382-5p and miR-127-3p in the sEVs isolated from Graves' tissue compared to those from benign tissue (false discovery rate; FDR p < 0.05). Similarly, miR-375-3p and miR-7-5p were also detected at a higher level in the Graves' tissue sEVs compared to the PTC tissue sEVs (FDR p < 0.05). No significant differences were observed between miRNA in sEVs from PTC vs. those from benign tissue. These results were supported by Quantitative Reverse Transcriptase Polymerase Chain Reaction (qRT-PCR). The novel findings demonstrate that the tissue-on-chip technology is a robust method for isolating sEVs directly from the tissue of interest, which has permitted the identification of four miRNAs, with which further investigation could be used as biomarkers or therapeutic targets within thyroid disease.

Autoimmune thyroid status in subclinical thyroid disorders in patients attending a tertiary care center in Nepal: a hospital-based cross-sectional study

BACKGROUND

Thyroid dysfunction is the leading endocrine disorder worldwide. Iodine deficiency disorders, which were once the major etiology of thyroid dysfunctions, now have been succeeded by autoimmune thyroid diseases with the rise in aberrant salt ionization protocols. This study endeavors to access the level of thyroid autoantibodies viz. anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (TGA), and anti-thyroid stimulating hormone receptor (TRAb) in individuals with subnormal thyroid profiles.

METHODS

This hospital-based cross-sectional study was conducted at the Department of Clinical Biochemistry, Tribhuvan University for a period of six months. Using non-probability (purposive) sampling method, a total of 60 patients were enrolled with subnormal thyroid profiles to include the population who have not yet started medication. Thyroid hormones (free T3, free T4, TSH) and thyroid antibodies (anti-TPO, TGA, and TRAb) were measured. For non-parametric data, Chi-square test and Kruskal-Wallis test were used. Spearman's correlation was done to determine the association between variables.

RESULTS

Out of 60 participants, the majority of the population between 25 and 44 years were diagnosed with thyroid dysfunction with female preponderance. Among all, 40% (n = 24) had subclinical hyperthyroid states while, 60% (n = 36) had subclinical hypothyroid states, and 75% (n = 45) of the total exhibited positive thyroid antibodies. In subclinical hypothyroid patients with TSH above 10 µIU/ml, anti TPO (58.5%) and TGA (66.7%) positivity were highly prevalent. On the other hand, TRAb was exclusively positive in hyperthyroid condition (50% among the group) which is by far the first of its kind reported in Nepal.

CONCLUSION

The rise in autoimmune thyroid disease among the Nepalese population infers that addressing iodine deficiency simply through salt iodinization may not be adequate to deal with the rising burden of thyroid disorders, especially in iodine-depleted areas. Also, the increasing prevalence of thyroid autoantibodies positivity in subclinical hypothyroidism in the Nepalese population accounts for the arduous screening and monitoring of autoimmune thyroid disorders in Nepal.

EFFECT OF THE C-TERMINUS OF TSHR ON T4 AND TRAB EXPRESSION IN BALB/C MICE

Context

The expression of TSHR-C on the serum tetraiodothyronine (T4) and TSH receptor antibody (TRAb) levels are rarely studied.

Objective

The effect of TSHR-c on T4 and TRAb levels and concomitant thyroid histological changes in mice was investigated.

Design

Animal experimental study.

Subjects and methods

Female BALB/c mice at 6-8 weeks of age were immunized with the thyroid stimulating hormone receptor antigen C-terminus (TSHR-C), and randomly divided into control group (treated with the corresponding concentrations of normal saline) and four experimental subgroups: TSHR-c1 subgroup (4 µg), TSHR-c2 subgroup (6 µg), TSHR-c3 subgroup (8 µg) and TSHR-c4 subgroup (10 µg). Serum T4 and TRAb levels were determined.

Results

The serum T4 level decreased significantly in the experimental mice as the concentration increased. All the experimental mice were positive for serum TRAb (experimental groups: 40 positive/40, 100% vs. control group: 3 positive/10, 30%) compared to the control group (P =0.000). HE staining showed that the follicles in the control mice were composed of small to medium-sized round follicles, whereas the follicles in the experimental mice were irregularly enlarged under light microscope.

Conclusions

TSHR-c immunization resulted in thyroid hormone changes like those observed in hypothyroidism, probably due to the induction of TRAb generation.

Thyroid autoantibodies

Thyroid-stimulating hormone (TSH) receptor antibody (TSH-R-Ab or TRAb) testing plays a pivotal role in arriving at the aetiological diagnosis in patients with thyrotoxicosis. A positive test establishes the diagnosis of Graves' disease (GD) while a negative result in conjunction with imaging studies supports other possible aetiologies. In patients with GD, TRAb levels at diagnosis and at the time of withdrawal of antithyroid drugs can identify patients who are unlikely to achieve remission and guide clinical management decisions. We provide an algorithm that incorporates TRAb in the decision-making process for the management of thyrotoxicosis. The utility of TRAb in predicting the risk of fetal and neonatal thyroid dysfunction is established and widely accepted in guidelines. TRAb may also help in the diagnosis of Graves' orbitopathy, especially in euthyroid or hypothyroid patients and its role in guiding its management is evolving as a useful adjunct to the clinical parameters used in making therapeutic decisions.Anti-thyroid peroxidase antibodies (TPOAb) and anti-thyroglobulin antibodies (TgAb) indicate thyroid autoimmunity. The most common use of TPOAb is to identify patients at a higher risk of progression to treatment-requiring hypothyroidism. They also aid the diagnosis of immune thyroiditis and Hashimoto's encephalopathy. Thyroglobulin measurement is used to help guide differentiated thyroid cancer treatment. TgAb is used as an accompanying test with thyroglobulin measurement as its presence can interfere with the thyroglobulin assay. A negative TgAb result reduces the likelihood of, but does not exclude, interference with thyroglobulin assay.

Regulatory mechanisms of microRNAs in endocrine disorders and their therapeutic potential

MicroRNAs (miRNAs) are small endogenous non-coding RNA molecules capable of regulating gene expression at the post-transcriptional level either by translational inhibition or mRNA degradation and have recently been importantly related to the diagnosis and prognosis of the most relevant endocrine disorders. The endocrine system comprises various highly vascularized ductless organs regulating metabolism, growth and development, and sexual function. Endocrine disorders constitute the fifth principal cause of death worldwide, and they are considered a significant public health problem due to their long-term effects and negative impact on the patient's quality of life. Over the last few years, miRNAs have been discovered to regulate various biological processes associated with endocrine disorders, which could be advantageous in developing new diagnostic and therapeutic tools. The present review aims to provide an overview of the most recent and significant information regarding the regulatory mechanism of miRNAs during the development of the most relevant endocrine disorders, including diabetes mellitus, thyroid diseases, osteoporosis, pituitary tumors, Cushing's syndrome, adrenal insufficiency and multiple endocrine neoplasia, and their potential implications as disease biomarkers.

Anti-TSH receptor antibodies (TRAb): Comparison of two third generation automated immunoassays broadly used in clinical laboratories and results interpretation

Graves’ disease (GD) is the most common cause of hyperthyroidism in iodine-replete populations. It is an autoimmune disease caused by autoantibodies to the TSHR (TRAb). Although the diagnostic is mainly clinical, measuring TRAb improves accuracy and provides valuable prognostic information. The aim of this study was to compare the performance of two of the most widely used immunoassays i.e., EliA™ anti-TSH-R and Elecsys^® anti-TSH-R. We have carried out a comparative study measuring TRAb by the two immunoassays in consecutive sera samples referred to the laboratory for TRAb measurement. Autoantibodies were measured in all samples in parallel by the two techniques. The two techniques were highly concordant as demonstrated by a Cohen’s kappa of 0.82. At the manufacturer recommended cut-off, sensitivity of Elecsys^® TRAb test was higher (100% vs. 96.6%), while specificity of the EliA™ TRAb test was higher (99.4% vs. 95.3%). In most patients TRAb are detected by any of two tests which are both well suited for Clinical Laboratories use. However, a higher specificity may constitute an advantage for measurement used not for screening but for diagnostic purposes, as anti-TSH-R is.

Alemtuzumab-Induced Autoimmune Thyroid Dysfunction

Alemtuzumab, a humanized monoclonal antibody used as a disease-modifying treatment in relapsing-remitting multiple sclerosis (RRMS), frequently causes autoimmunity as its principal adverse effect. We describe a typical case of a young man treated with two courses of alemtuzumab presenting 18 months later with initial hyperthyroidism due to Graves’ disease (GD) followed by persistent hypothyroidism. We discuss the pathophysiological role of stimulating and blocking thyrotropin receptor antibodies in the development of alemtuzumab-induced autoimmune thyroid dysfunction and clinical challenges posed by spontaneous, bidirectional switching between hyperthyroidism and hypothyroidism. Guidelines recommend monitoring thyroid function pre-treatment and every three months for four years following alemtuzumab treatment. Patient education is crucial for maintaining adherence to monitoring programs.

Evaluation of analytic and clinical performance of two immunoassays for detecting thyroid-stimulating receptor antibody in the diagnosis of Graves' disease

Objective

To evaluate the analytical and clinical performance of two immunoassays for diagnosis of Graves’ disease (GD), the Immulite thyroid‐stimulating immunoglobulin (TSI), and Elecsys Anti‐TSH receptor (TSHR) assay.

Methods

Precision and analytical measurement range were assessed using pooled samples of patients. The comparison between the two methods was evaluated using 579 clinical samples, and receiver operating characteristic (ROC) curves were drawn using the final diagnosis as reference. Clinical sensitivity and specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the two tests.

Results

The repeatability and intermediate imprecision coefficient of variation (CV%) of the TSI assay were 3.8% and 4.1% at 0.95 IU/L, and 3.5% and3.6% at 19.5 IU/L, respectively. The assays were linear over a range 0.27–38.5 IU/L. There was a high correlation between the quantitative results of the two methods (correlation coefficient r = 0.930). The cut‐off value obtained by ROC analysis for TSI assay was 0.7 IU/L with sensitivity of 93.7% and specificity of 85.1%. An overall qualitative agreement of 91.5% between two methods was observed. Among 44 patients with discordant qualitative results, the TSI assay provided more satisfactory results consistent with clinical diagnoses.

Conclusion

The TSI assay showed excellent analytical performance and provided a high PPV for GD.

Graves' disease in a patient with Down syndrome: a shift from hyperthyroidism to hypothyroidism

Down syndrome (DS) is associated with an increased risk of multisystemic dysfunction, namely endocrine abnormalities. Thyroid dysfunction is the most common endocrinological disorder, and it can manifest as either hypothyroidism or hyperthyroidism. A 16-year-old patient with DS developed hyperthyroidism after a lifetime of alternating between subclinical hypothyroidism and euthyroidism. He presented new onset weight loss, agitation and diarrhoea. Laboratory studies were compatible with hyperthyroidism. Thyroid receptor antibodies (TRAbs) were positive, antithyroid peroxidase antibodies and thyroglobulin antibodies were negative. Antithyroid medication (methimazole) was prescribed and, despite therapy adjustments, laboratory evaluation revealed new onset hypothyroidism with persistently positive TRAbs. He experienced weight gain and remained in a hypothyroid state even with withdrawal of methimazole and administration of levothyroxine. This case illustrates an example of Graves' disease with coexisting stimulating and inhibiting TRAbs that led to a shift from hyperthyroidism to hypothyroidism, a rare condition in patients with DS.

Evaluation of the application of TSH receptor stimulating autoantibodies and the optimization of detection strategy in Graves' disease

BACKGROUND

We evaluated the use of thyroid stimulating immunoglobulin (TSI) assay to optimize the detection strategy for Graves' disease.

METHODS

Five hundred and forty-four well characterized serum samples from the Clinical Laboratory of Shanghai Tongren Hospital were collected from August 2019 to April 2020. The serum samples were obtained from 52 untreated GD patients, 155 treated GD patients, 83 patients with Hashimoto's thyroiditis, 70 patients with thyroid nodules, 83 patients with thyroid cancer, and 101 healthy subjects. All samples were evaluated by both TSI assay and TSH receptor autoantibodies (TRAb) assay. Moreover, 23 patients without a distinct thyroid disease diagnosis at the first visit were monitored for 6 months to make a final diagnosis.

RESULTS

The clinical sensitivity of the TSI and TRAb assays was 98.10% and 94.20% respectively, while the clinical specificity was 92.30% and 96.70% respectively. ROC plot analysis based on sera of UT-GD (newly diagnosed GD patients) revealed an area under the curve (AUC) of 0.974 for the TSI assay. The best cutoff value was 0.58 IU/l (98.0% of sensitivity, 92.8% of specificity). The AUC for the TRAb assay was 0.961. Furthermore, combining TSI and TRAb results, the area under the curve was 0.981. In a pilot study of 23 patients with an uncertain initial diagnosis, the follow-up results showed the clinical diagnosis of 22 out of 23 cases were resolved in agreement with the results obtained by the TSI assay, and one case matched the result obtained by TRAb assay.

CONCLUSION

The TSI assay presents very promising analytical characteristics and could be adopted in clinical practice to improve GD diagnosis. The TSI assay might be better than TRAb assay in initial differential diagnosis of GD from other thyroid diseases.

The role of laboratory medicine in the diagnosis of the hyperthyroidism

Hyperthyroidism is a clinical condition characterized by inappropriately high synthesis and secretion of thyroid hormones by the thyroid gland. It has multiple aetiologies, manifestations and potential therapies. Graves' disease is the most common form of hyperthyroidism, due to the production of autoantibodies against thyrotropin receptor, capable of over-stimulating thyroid function. A reliable diagnosis of hyperthyroidism can be established on clinical grounds, followed by the evaluation of serum thyroid function tests (thyrotropin first and then free thyroxine, adding the measurement of free triiodothyronine in selected specific situations). The recent guidelines of both the American and European Thyroid Associations have strongly recommended the measurement of thyrotropin receptor autoantibodies for the accurate diagnosis and management of Graves' disease. If autoantibody test is negative, a radioiodine uptake should be performed. Considering the most recent laboratory improvements, binding assays can be considered the best first solution for the measurement of thyrotropin receptor autoantibodies in diagnosis and management of overt cases of Graves' disease. In fact, they have a satisfactory clinical sensitivity and specificity (97.4% and 99.2%, respectively) being performed in clinical laboratories on automated platforms together with the other thyroid function tests. In this setting, the bioassays should be reserved for fine and complex diagnoses and for particular clinical conditions where it is essential to document the transition from stimulating to blocking activity or vice versa (e.g. pregnancy and post-partum, related thyroid eye disease, Hashimoto's thyroiditis with extrathyroidal manifestations, unusual cases after LT4 therapy for hypothyroidism or after antithyroid drug treatment for Graves' disease). Undoubtedly, technological advances will help improve laboratory diagnostics of hyperthyroidism. Nevertheless, despite future progress, the dialogue between clinicians and laboratory will continue to be crucial for an adequate knowledge and interpretation of the laboratory tests and, therefore, for an accurate diagnosis and correct management of the patient.

Thyrotropin receptor antibody immunoassays may not be reliable in confirming diagnosis of Painless Thyroiditis

BACKGROUND

Scintigraphy using 99mTc-pertechnetate (TS) is the diagnostic test to differentiate thyroiditis following Graves' disease (GD) from painless thyroiditis (PT). However, TS may be contraindicated or unavailable.

OBJECTIVE

We compared the diagnostic effectiveness of two TSH receptor antibody (TRAb) immunoassays in untreated PT, already confirmed by qualitative and quantitative(99m) Tc-pertechnetate thyroid uptake (TCTU).

METHOD

TRAb assay and TS were performed in suspected PT patients. All 67 subjects (27 males) with confirmed diagnosis of PT based on qualitative (subjective) low uptake and quantitative uptake below 0.4% (Normal TcTU: 0.4-4%). During the period of study, we used two 2^nd generation TRAb assays.

RESULT

Mean age, TSH, free T4 and TcTU were 40.5± 12.7 years, 0.066±0.089 mIU/L, 2.46±2.18 ng/mL and 0.188±0.0503% respectively. Fifteen (22.39%) of our PT patients were TRAb positive. Sensitivity, specificity, accuracy, PPV and NPV of TRAb in predicting thyroiditis were 81%, 75%, 78.2%, 83.6% and 74.4% in Assay 1. The same parameters were 74%, 64%, 71.2%, 76.8% and 62.7% respectively in TRAb Assay 2. However, ROC curve did not reveal any difference between the two assays.

CONCLUSION

Negative TRAb value does not reliably distinguish PT from mild GD, in situations where TS is contraindicated or unavailable.

Graves' disease

Graves' disease (GD) is an autoimmune disease that primarily affects the thyroid gland. It is the most common cause of hyperthyroidism and occurs at all ages but especially in women of reproductive age. Graves' hyperthyroidism is caused by autoantibodies to the thyroid-stimulating hormone receptor (TSHR) that act as agonists and induce excessive thyroid hormone secretion, releasing the thyroid gland from pituitary control. TSHR autoantibodies also underlie Graves' orbitopathy (GO) and pretibial myxoedema. Additionally, the pathophysiology of GO (and likely pretibial myxoedema) involves the synergism of insulin-like growth factor 1 receptor (IGF1R) with TSHR autoantibodies, causing retro-orbital tissue expansion and inflammation. Although the aetiology of GD remains unknown, evidence indicates a strong genetic component combined with random potential environmental insults in an immunologically susceptible individual. The treatment of GD has not changed substantially for many years and remains a choice between antithyroid drugs, radioiodine or surgery. However, antithyroid drug use can cause drug-induced embryopathy in pregnancy, radioiodine therapy can exacerbate GO and surgery can result in hypoparathyroidism or laryngeal nerve damage. Therefore, future studies should focus on improved drug management, and a number of important advances are on the horizon.

Effect of Graves' disease on the prognosis of differentiated thyroid carcinoma: a meta-analysis

PURPOSE

Several studies have reported different findings on the prognosis of differentiated thyroid carcinoma combined with Graves' disease. To assess the effect of Graves' disease on differentiated thyroid carcinoma, a meta-analysis was undertaken.

METHODS

PubMed, OVID and the Cochrane Library were systematically searched for trials published prior to Oct. 2018. Studies containing data on the outcomes of Graves' disease with differentiated thyroid carcinoma were included. Summary estimates of the prevalence of recurrence/disease progression/persistence and mortality as well as odds ratios and weighted mean differences were calculated with a random-effects model.

RESULTS

Of the 916 related articles found, 13 fulfilled the inclusion criteria. The recurrence/disease progression/persistent rate was not significantly different between the Graves' disease group and the non-Graves' disease group (P = 0.86). However, the analysis of three studies with K-M curves or HRs showed that there was a significant difference between the two groups (P = 0.04). Subgroup analysis showed that the contradictory results could be due to the location/race assessed in the studies. Graves' disease almost acted as a risk factor (OR = 1.77, 95%C.I. = 0.99-3.16) for differentiated thyroid carcinoma in European studies. When heterogeneous studies were excluded, the analyses show that GD was a risk factor for recurrence/disease progression/persistence (P = 0.03, OR = 1.75, 95%C.I. = 1.04-2.95). The overall mortality rate was significantly higher in the Graves' disease group than in the non-Graves' disease group (P = 0.02, OR = 2.93, 95%C.I. = 1.17-7.37).

CONCLUSIONS

Graves' disease acts as a risk factor for the prognosis of differentiated thyroid carcinoma. The recurrence/disease progression/persistent rate may be affected by TSAbs in a specific location/race and with a genetic immunization background. However, the histotypes and subtypes may play an important role in mortality rate.

Diagnostic testing for Graves' or non-Graves' hyperthyroidism: A comparison of two thyrotropin receptor antibody immunoassays with thyroid scintigraphy and ultrasonography

OBJECTIVE

Graves' disease (GD) is the most common cause of hyperthyroidism. In many cases, when the aetiological diagnosis of GD is not evident based on the clinical evaluation and thyroid function testing, it may become challenging to distinguish Graves' hyperthyroidism from other forms of thyrotoxicosis. The current study was primarly carried out to compare the diagnostic effectiveness of two TSH receptor antibody immunoassays (IMAs), ultrasonography and thyroid scintigraphy in hyperthyroidism scenario.

METHODS

We retrospectively analysed consecutive patients with newly diagnosed and untreated thyrotoxicosis who underwent thyroid functional tests, both TRAb and TSI measurements, thyroid scintigraphy and ultrasonography. TRAb assessment was carried out by Kryptor^® compact PLUS, while TSI by Immulite^® . Echo pattern 3 corresponded to 'thyroid inferno', and the final diagnosis of GD vs non-Graves' hyperthyroidism was made according to the thyroid scan (qualitative scintigraphy). Receiver operating characteristic (ROC) curves were drawn using the final diagnosis as reference. Clinical sensitivity and specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for all the tests.

RESULTS

A total of 124 untreated hyperthyroid patients were included in our study (GD, n = 86 vs non-Graves' hyperthyroidism, n = 38). ROC curves showed that the optimal cut-off values associated with the highest diagnostic sensitivity and specificity was 0.7 IU/L for TRAb Kryptor^® (93 [85.4-97.4] and 86.8 [71.9-95.5]) and 0.1 IU/L for TSI Immulite^® (94.2 [86.9-98.1] and 84.2 [68.7-93.9]), respectively. For the echo pattern 3, we found a good sensitivity (92.1%) and a high PPV (95.2%) but a quite low specificity value (69.8%) and a relative low NPV (57.5%). For thyroid scintigraphy, the TcTU cut-off value of 1.3% corresponded to the best limit for sensitivity and specificity in our patients (95.3 [88.5-98.7] and 96.4 [81.6-99.4]). The Passing-Bablok regression equation and the Bland-Altman test showed a great degree of correlation and agreement existed between TRAb Kryptor^® and Immulite^® TSI results.

CONCLUSIONS

Thyroid scintigraphy remains the most accurate method to differentiate causes of thyrotoxicosis. However, TRAb assays can be alternatively adopted in this setting, limiting the use of thyroid scintigraphy (TcTU evaluation) to TRAb-negative patients. Thyoid US is less accurate than both TRAb/TSI and thyroid scintigraphy, but the 'thyroid inferno' pattern provides a high PPV for GD.

Thyro-entero-gastric autoimmunity: Pathophysiology and implications for patient management

The association between autoimmune atrophic gastritis and thyroid disorders has been observed since the early 1960s and the expression "thyrogastric syndrome" was coined to indicate the presence of thyroid autoantibodies or autoimmune thyroid disease in patients with pernicious anemia, a late clinical stage of autoimmune atrophic gastritis. More recently, it was confirmed that autoimmune thyroid disorders, in particular Hashimoto's thyroiditis, may be frequently associated with other organ-specific, immune-mediated disorders, such as autoimmune atrophic gastritis or celiac disease. The association of Hashimoto's thyroiditis with autoimmune atrophic gastritis or celiac disease in adult patients is currently considered part of the polyglandular autoimmune syndromes which include several autoimmune disorders associated with an autoaggressive impairment of endocrine glands. From a clinical point of view, the thyro-entero-gastric autoimmunity may lead to potentially serious consequences like anemia, micronutrients deficiencies, and drugs malabsorption, as well as to an increased risk for malignancies. These alterations may frequently present in an underhand manner, with consequent diagnostic and treatment delays. Many aspects of the association between thyroid, gastric and intestinal autoimmune diseases still await clarification. The present review focuses on the embryological, genetic and pathophysiological aspects of thyro-entero-gastric autoimmunity. In particular, the current diagnostic criteria of autoimmune thyroid disease, autoimmune atrophic gastritis, and celiac disease are reviewed, along with the evidences for their association in poly-autoimmunity syndromes. The benefits of proactive screening of autoimmune thyroid disorders in patients with autoimmune gastritis or enteropathy and viceversa are also discussed.

[Progress in the research of negative feedback effect of thyroglobulin]

Thyroglobulin is the most important and abundant protein in thyroid follicles and has been widely studied as a tumor marker of thyroid cancer recurrence and persistence. Tg is considered the material basis of thyroid hormone synthesis and does not participate in the regulation of thyroid hormone synthesis and secretion. This review summarizes the recent progress in the research of thyroid hormone synthesis and secretion regulation via a negative feedback regulation mechanism by the thyroid-hypothalamus-pituitary axis. Thyroglobulin can negatively regulate the synthesis of thyroid hormone by thyroid follicular cells and antagonize the positive regulation of thyrotropin TSH. The function of thyroid follicular cells is presumably a result of Tg and TSH interaction, and a follicular cycle model is proposed to explain the causes of follicular heterogeneity in glands. We also discuss the prospects and clinical significance of studies into the negative feedback regulation mechanism of the thyroid-hypothalamus-pituitary axis and compare two theories for this mechanism.