The relative importance of genetic and environmental factors in the aetiology of thyroid nodularity: a study of healthy Danish twins

Exome sequencing to explore the possibility of predicting genetic susceptibility to the joint occurrence of polycystic ovary syndrome and Hashimoto's thyroiditis

A large body of evidence indicates that women with polycystic ovary syndrome (PCOS) have a higher risk of developing Hashimoto's thyroiditis (HT) than healthy individuals. Given the strong genetic impact on both diseases, common predisposing genetic factors are possibly involved but are not fully understood. Here, we performed whole-exome sequencing (WES) for 250 women with sporadic PCOS, HT, combined PCOS and HT (PCOS+HT), and healthy controls to explore the genetic background of the joint occurrence of PCOS and HT. Based on relevant comparative analyses, multivariate logistic regression prediction modeling, and the most informative feature selection using the Monte Carlo feature selection and interdependency discovery algorithm, 77 variants were selected for further validation by TaqMan genotyping in a group of 533 patients. In the allele frequency test, variants in RAB6A, GBP3, and FNDC7 genes were found to significantly (padjusted < 0.05) differentiated the PCOS+HT and PCOS groups, variant in HIF3A differentiated the PCOS+HT and HT groups, whereas variants in CDK20 and CCDC71 differentiated the PCOS+HT and both single disorder groups. TaqMan genotyping data were used to create final prediction models, which differentiated between PCOS+HT and PCOS or HT with a prediction accuracy of AUC = 0.78. Using a 70% cutoff of the prediction score improved the model parameters, increasing the AUC value to 0.87. In summary, we demonstrated the polygenic burden of both PCOS and HT, and many common and intersecting signaling pathways and biological processes whose disorders mutually predispose patients to the development of both diseases.

Genetic susceptibility to hereditary non-medullary thyroid cancer

Non-medullary thyroid cancer (NMTC) is the most common type of thyroid cancer. With the increasing incidence of NMTC in recent years, the familial form of the disease has also become more common than previously reported, accounting for 5-15% of NMTC cases. Familial NMTC is further classified as non-syndromic and the less common syndromic FNMTC. Although syndromic NMTC has well-known genetic risk factors, the gene(s) responsible for the vast majority of non-syndromic FNMTC cases are yet to be identified. To date, several candidate genes have been identified as susceptibility genes in hereditary NMTC. This review summarizes genetic predisposition to non-medullary thyroid cancer and expands on the role of genetic variants in thyroid cancer tumorigenesis and the level of penetrance of NMTC-susceptibility genes.

An overview of retrosternal goiter

Goiters tend to grow slowly and steadily over many years, occasionally reaching the mediastinum and extending through the thoracic inlet into the visceral compartment. In most cases, retrosternal goiters originate from the cervical portion of the thyroid. The incidence of retrosternal goiters varies considerably, ranging from 0.2 to 45% of all thyroidectomies, depending on the criteria used to define this type of goiter. Symptoms are generally related to the compressive nature of the mass on the adjacent structures, and most patients report some form of respiratory manifestation associated with the goiter. A diagnostic assessment usually includes an evaluation of thyroid function, chest radiography, and computed tomography. Fine-needle aspiration biopsy should be avoided in substernal areas of the goiter due to limited visibility and location of vital structures in this region. Treatment of retrosternal goiters is surgical, as medical therapy is generally unsuccessful in these cases.

Genetic Susceptibility to Joint Occurrence of Polycystic Ovary Syndrome and Hashimoto's Thyroiditis: How Far Is Our Understanding?

Polycystic ovary syndrome (PCOS) and Hashimoto’s thyroiditis (HT) are endocrine disorders that commonly occur among young women. A higher prevalence of HT in women with PCOS, relative to healthy individuals, is observed consistently. Combined occurrence of both diseases is associated with a higher risk of severe metabolic and reproductive complications. Genetic factors strongly impact the pathogenesis of both PCOS and HT and several susceptibility loci associated with a higher risk of both disorders have been identified. Furthermore, some candidate gene polymorphisms are thought to be functionally relevant; however, few genetic variants are proposed to be causally associated with the incidence of both disorders together.

Familial Aggregation and Heritability of Nonmedullary Thyroid Cancer in an Asian Population: A Nationwide Cohort Study

PURPOSE

The purpose of this work is to assess the extent of familial aggregation of nonmedullary thyroid cancer (NMTC) and the relative risks (RRs) of chronic thyroid diseases and common malignancies in first-degree relatives of NMTC patients.

METHODS

In the National Health Insurance Research database of Taiwan, all eligible individuals in 2016 were analyzed (n = 23 696 659) and the family structures of 38 686 patients diagnosed with NMTC between 1997 and 2016 were identified. The prevalence and RRs of NMTC, chronic thyroid diseases, and common malignancies in individuals with first-degree relatives with NMTC were examined. The accountability of heritability and environmental factors to NMTC susceptibility was estimated using the polygenic liability model.

RESULTS

The prevalence of NMTC was 0.16% in the general population and 0.64% in individuals with first-degree relatives with NMTC. Regarding affected relatives, the RR (95% CI) for NMTC was 20.12 (4.86-83.29) for twins, 6.43 (4.80-8.62) for siblings, 5.24 (4.55-6.03) for offspring, 5.07 (4.41-5.81) for parents, and 2.07 (1.53-2.81) for spouses. The estimated genetic, common environmental, and nonshared environmental contributions to NMTC were 28.0%, 14.3%, and 57.7%, respectively. A family history of NMTC was associated with higher risks of thyroid nodules (RR, 2.26; 95% CI, 2.18-2.35), Hashimoto thyroiditis (2.11; 1.89-2.36), Graves disease (1.49; 1.42-1.57), lung cancer (1.56; 1.32-1.85), and leukemia and lymphoma (1.24; 1.03-1.50).

CONCLUSION

Our findings demonstrate the importance of genetic and environmental contributions to NMTC susceptibility and highlight the coaggregation of chronic thyroid diseases and multiple malignancies with NMTC.

Decreased Immunoglobulin G Core Fucosylation, A Player in Antibody-dependent Cell-mediated Cytotoxicity, is Associated with Autoimmune Thyroid Diseases

Autoimmune thyroid diseases (AITD) are the most common group of autoimmune diseases, associated with lymphocyte infiltration and the production of thyroid autoantibodies, like thyroid peroxidase antibodies (TPOAb), in the thyroid gland. Immunoglobulins and cell-surface receptors are glycoproteins with distinctive glycosylation patterns that play a structural role in maintaining and modulating their functions. We investigated associations of total circulating IgG and peripheral blood mononuclear cells glycosylation with AITD and the influence of genetic background in a case-control study with several independent cohorts and over 3,000 individuals in total. The study revealed an inverse association of IgG core fucosylation with TPOAb and AITD, as well as decreased peripheral blood mononuclear cells antennary α1,2 fucosylation in AITD, but no shared genetic variance between AITD and glycosylation. These data suggest that the decreased level of IgG core fucosylation is a risk factor for AITD that promotes antibody-dependent cell-mediated cytotoxicity previously associated with TPOAb levels.

Dysregulated Antibody, Natural Killer Cell and Immune Mediator Profiles in Autoimmune Thyroid Diseases

The pathogenesis of autoimmune thyroid diseases (AITD) is poorly understood and the association between different immune features and the germline variants involved in AITD are yet unclear. We previously observed systemic depletion of IgG core fucosylation and antennary α1,2 fucosylation in peripheral blood mononuclear cells in AITD, correlated with anti-thyroid peroxidase antibody (TPOAb) levels. Fucose depletion is known to potentiate strong antibody-mediated NK cell activation and enhanced target antigen-expressing cell killing. In autoimmunity, this may translate to autoantibody-mediated immune cell recruitment and attack of self-antigen expressing normal tissues. Hence, we investigated the crosstalk between immune cell traits, secreted proteins, genetic variants and the glycosylation patterns of serum IgG, in a multi-omic and cross-sectional study of 622 individuals from the TwinsUK cohort, 172 of whom were diagnosed with AITD. We observed associations between two genetic variants (rs505922 and rs687621), AITD status, the secretion of Desmoglein-2 protein, and the profile of two IgG N-glycan traits in AITD, but further studies need to be performed to better understand their crosstalk in AITD. On the other side, enhanced afucosylated IgG was positively associated with activatory CD335- CD314+ CD158b+ NK cell subsets. Increased levels of the apoptosis and inflammation markers Caspase-2 and Interleukin-1α positively associated with AITD. Two genetic variants associated with AITD, rs1521 and rs3094228, were also associated with altered expression of the thyrocyte-expressed ligands known to recognize the NK cell immunoreceptors CD314 and CD158b. Our analyses reveal a combination of heightened Fc-active IgG antibodies, effector cells, cytokines and apoptotic signals in AITD, and AITD genetic variants associated with altered expression of thyrocyte-expressed ligands to NK cell immunoreceptors. Together, TPOAb responses, dysregulated immune features, germline variants associated with immunoactivity profiles, are consistent with a positive autoreactive antibody-dependent NK cell-mediated immune response likely drawn to the thyroid gland in AITD.

Natural History of Contralateral Nodules After Lobectomy in Patients With Papillary Thyroid Carcinoma

BACKGROUND

Bilateral thyroid nodularity is considered an indication for total thyroidectomy in papillary thyroid carcinoma (PTC). However, the natural history and outcome of contralateral nodules have never been studied.

OBJECTIVE

To investigate the natural history of nonsuspicious contralateral nodules after lobectomy for PTC.

METHODS

We included patients who had one or more solid nodules (≥3 mm) in the contralateral lobe with benign cytology before surgery or small nonsuspicious nodules per ultrasonography.

RESULTS

One hundred and twelve patients were included. Median age was 57 years, and median size of the PTC (initial lobectomy) was 8 mm (range, 0.5 to 28 mm). On the contralateral side, the median size of nodules was 7 mm (range, 3 to 30 mm). Thirty-three nodules (29%) had fine-needle aspiration (FNA) before surgery, and all were benign. After a median follow-up of 6 years, median growth was zero (range, -20 to 19 mm). Twenty-six nodules (23%) increased ≥3 mm in size (median, 6 mm; range, 4 to 19 mm). Twenty patients (18%) developed new nodules. Twelve patients (11%) underwent completion thyroidectomy for growth (three), suspicious FNA (seven; Bethesda III to V), malignancy (one), or unknown reason (one). Overall, according to the completion thyroidectomy specimen, six patients (5%) were diagnosed with contralateral PTC (five micro-PTCs, one 20 mm), and all were without evidence of disease at the end of follow-up. There were no surgical difficulties or local complications during completion surgery.

CONCLUSIONS

Lobectomy for low-risk patients with a small PTC and nonsuspicious contralateral thyroid nodule(s) is a reliable and safe initial treatment option. In the few patients who required completion thyroidectomy, treatment with surgery and radioiodine was effective.

Human Exposures to Bisphenol A, Bisphenol F and Chlorinated Bisphenol A Derivatives and Thyroid Function

Although the increasing prevalence of thyroid nodular disease (TND) has been partially attributed to the more frequent usage of improved diagnostics, environmental factors, such as exposures to thyroid-disrupting chemicals may contribute to TND and altered thyroid function. We investigated the association between exposures to bisphenol A (BPA), its chlorinated derivatives (ClxBPA), and bisphenol F (BPF) with TND and thyroid measures in adult women. A case-control study in Cyprus and Romania (n = 212) was conducted, where cases were those with thyroid nodules (diameter >3mm), and controls without nodules. Serum TSH and free thyroxine and urinary levels of BPA, BPF and ClxBPA were measured using immunoassays and tandem mass spectrometry, respectively. The association between exposures to BPA compounds and TND, adjusting for age, BMI, thyroid hormones and urinary iodine was assessed using logistic regression. Linear regression was used to explore associations between urinary BPA, BPF and ClxBPA and serum thyroid hormones. With the exception of a chlorinated BPA compound (30%), the rest of bisphenols were quantified in 100% of urine samples. A positive and significant (p<0.05) association was observed between urinary BPA and serum TSH that remained after adjusting for urinary creatinine, age, BMI, study site and disease status; there was no significant association between BPF or ClxBPA with TSH. None of the BPA compounds were associated with higher odds of TND. Our study found associations of urinary BPA with TSH but not with BPF or ClxBPA. A larger study would be justified.

Genetic and non-iodine-related factors in the aetiology of nodular goitre

Genetic and a large number of environmental non-iodine-related factors play a role in the cause of nodular goitre. Most evidence for the influence of genetic and environmental factors in the cause of goitre is from cross-sectional, population-based studies. Only a few studies have included prospective data on risk factors for nodular goitre, although few prospective data are available on the effect of iodine and tobacco smoking on goitre development. Goitre is not one single phenotype. Many epidemiological studies do not distinguish diffuse from nodular goitre, as the investigated parameter is often thyroid volume or frequency with increased thyroid volume. Moreover, information on the presence and effect of gene-environment, gene-gene, and environment-environment effect modifications is limited. Thus, firm conclusions about the relative contributions and causality of the investigated risk factors should be made with caution. Smoking seems to be an established risk factor for nodular goitre, possibly with effect modification from iodine intake, as the risk associated with smoking is smaller or absent in areas with sufficient iodine intake. The use of oral contraceptives might have protective effects against goitre, and childbirth is an increased risk factor for goitre in areas with non-optimal iodine intake. Insulin resistance is a recently investigated risk factor, and the risk of goitre may be reversible with metformin treatment. Iodine remains the major environmental risk factor for nodular goitre.

Relationship between metabolic syndrome and multinodular non-toxic goiter in an inpatient population from a geographic area with moderate iodine deficiency

BACKGROUND

Obesity and insulin resistance predispose individuals to the development of both metabolic syndrome and non-toxic nodular thyroid diseases.

AIM

The aim of this observational, cross-sectional study is to evaluate the relationship between metabolic syndrome and multinodular nontoxic goiter in an inpatient population from a geographic area with moderate iodine deficiency.

SUBJECTS AND METHODS

We examined 1422 Caucasian euthyroid inpatients. Thyroid volume was determined by ultrasound of the neck. A fine-needle aspiration biopsy was performed to evaluate single thyroid nodules and dominant nodules ≥15 mm in euthyroid multinodular goiter. The diagnosis of metabolic syndrome was made according to the criteria of the American Heart Association/ National Heart, Lung, and Blood Institute.

RESULTS

Of the sample, 277 patients had clinical evidence of multinodular nontoxic goiter, 461 met the criteria for the diagnosis of metabolic syndrome, and 132 were found to have both conditions. After adjusting for age, gender, body mass index, nicotinism, parity, alcohol intake, thyroid function, and metabolic syndrome- related pharmacological treatment, metabolic syndrome was found to be an independent risk factor for the occurrence of multinodular non-toxic goiter. The relationship between metabolic syndrome and multi nodular non-toxic goiter was apparent in both men and women.

CONCLUSIONS

In this study of euthyroid inpatients, we demonstrate that metabolic syndrome is an independent risk factor for the occurrence of multinodular non-toxic goiter in a geographic area with moderate iodine deficiency. We propose that patients meeting the criteria for metabolic syndrome should be screened for the presence of multinodular non-toxic goiter.

Guidelines of the French society of endocrinology for the management of thyroid nodules

The present document is a follow-up of the clinical practice guidelines of the French Society of Endocrinology, which were established for the use of its members and made available to scientific communities and physicians. Based on a critical analysis of data from the literature, consensuses and guidelines that have already been published internationally, it constitutes an update of the report on the diagnostic management of thyroid nodules that was proposed in France, in 1995, under the auspices of the French National Agency for Medical Evaluation (l'Agence nationale d'évaluation médicale). The current guidelines were deliberated beforehand by a number of physicians that are recognised for their expertise on the subject, coming from the specialities of endocrinology (the French Thyroid Research Group) and surgery (the French Association for Endocrine Surgery), as well as representatives from the fields of biology, ultrasonography, cytology and nuclear medicine. The guidelines were presented and submitted for the opinion of the members of the Society at its annual conference, which was held in Nice from 7-10 October 2009. The amended document was posted on the website of the Society and benefited from additional remarks of its members. The final version that is presented here was not subjected to methodological validation. It does not claim to be universal in its scope and will need to be revised in concert with progress made in technical and developmental concepts. It constitutes a document that the Society deems useful for distribution concerning the management of thyroid nodules, which is current, efficient and cost effective.

Thyroid nodules, polymorphic variants in DNA repair and RET-related genes, and interaction with ionizing radiation exposure from nuclear tests in Kazakhstan

Risk factors for thyroid cancer remain largely unknown except for ionizing radiation exposure during childhood and a history of benign thyroid nodules. Because thyroid nodules are more common than thyroid cancers and are associated with thyroid cancer risk, we evaluated several polymorphisms potentially relevant to thyroid tumors and assessed interaction with ionizing radiation exposure to the thyroid gland. Thyroid nodules were detected in 1998 by ultrasound screening of 2997 persons who lived near the Semipalatinsk nuclear test site in Kazakhstan when they were children (1949-1962). Cases with thyroid nodules (n = 907) were frequency matched (1:1) to those without nodules by ethnicity (Kazakh or Russian), gender and age at screening. Thyroid gland radiation doses were estimated from fallout deposition patterns, residence history and diet. We analyzed 23 polymorphisms in 13 genes and assessed interaction with ionizing radiation exposure using likelihood ratio tests (LRT). Elevated thyroid nodule risks were associated with the minor alleles of RET S836S (rs1800862, P = 0.03) and GFRA1 -193C>G (rs not assigned, P = 0.05) and decreased risk with XRCC1 R194W (rs1799782, P trend = 0.03) and TGFB1 T263I (rs1800472, P = 0.009). Similar patterns of association were observed for a small number of papillary thyroid cancers (n = 25). Ionizing radiation exposure to the thyroid gland was associated with significantly increased risk of thyroid nodules (age and gender adjusted excess odds ratio/Gy = 0.30, 95% CI 0.05-0.56), with evidence for interaction by genotype found for XRCC1 R194W (LRT P value = 0.02). Polymorphisms in RET signaling, DNA repair and proliferation genes may be related to risk of thyroid nodules, consistent with some previous reports on thyroid cancer. Borderline support for gene-radiation interaction was found for a variant in XRCC1, a key base excision repair protein. Other pathways such as genes in double-strand break repair, apoptosis and genes related to proliferation should also be pursued.

No link between X chromosome inactivation pattern and simple goiter in females: evidence from a twin study

BACKGROUND

Simple goiter (SG) comprises diffuse (DG) and nodular (NG) benign nonautoimmune nontoxic goiter. In nonendemic goiter areas, the ratio of females to males may exceed 5:1, indicating that gender and/or sex hormones may play a role in the etiology of SG in these areas. Theoretically, as shown for autoimmune thyroid disease, X chromosome inactivation (XCI) and resultant tissue chimerism could offer a novel explanation for the female preponderance of SG. To examine whether skewed XCI is associated with SG, we first compared XCI in 71 twin individuals with SG with that in 142 unrelated healthy control twin individuals, and then performed a within-pair comparison of XCI in 48 twin pairs discordant for SG.

METHODS

DNA was extracted from peripheral blood cells. XCI analysis was performed by predigestion of DNA using the methylation-sensitive enzyme Hpall, followed by polymerase chain reaction of the polymorphic CAG repeat of the androgen receptor gene. A polymerase chain reaction product is obtained from the inactive X chromosome only. The XCI pattern was classified as skewed when 80% or more of the cells preferentially inactivated the same X chromosome. Twin zygosity was established by DNA fingerprinting.

RESULTS

The frequency of skewed XCI in female twins with SG, DG, and NG was 11% (8/71), 13% (6/46), and 8% (2/25), respectively, which was not significantly different from the prevalences in the corresponding control populations, 14% (20/142, p = 0.56), 14% (13/92, p = 1.00), and 14% (7/50, p = 0.71), respectively. Essentially, similar results were obtained when comparing the prevalence of skewed XCI in twin pairs discordant for SG (48 pairs), DG (30 pairs), and NG (18 pairs).

CONCLUSION

In a sample of Danish female twins, we did not find evidence for involvement of skewed XCI in the etiology or the female preponderance of SG.