Associations between vitamin D levels and dietary patterns in patients with Hashimoto's thyroiditis.

Introduction: Vitamin D insufficiency is a global health problem affecting healthy and diseased individuals, including patients with Hashimoto's thyroiditis (HT). Identifying dietary factors that may affect vitamin D levels and providing dietary guidelines accordingly can alleviate this problem. We therefore aimed to identify still unknown associations of dietary patterns, assessed through the Food Frequency Questionnaire (FFQ) with vitamin D blood levels. Materials and methods: FFQ was collected from 459 patients from Croatian Biobank of Patients with Hashimoto's thyroiditis (CROHT), while total 25(OH)D was measured from their stored serum samples. We performed linear regression analysis between vitamin D levels and weekly intake of 24 food groups in 459 patients with HT (ALL), and in two disease-severity groups (MILD and OVERT). Results: The main results of our study are observations of: (1) an inverse association between vitamin D levels and coffee consumption (ALL: ß = -0.433, p = 0.005; OVERT: ß = -0.62, p = 0.008); (2) an inverse association between vitamin D levels and sweets consumption (ALL: ß = -0.195, p = 0.034; OVERT: ß = -0.431, p = 0.006); (3) positive association between vitamin D levels and vegetable consumption (ALL: ß = 0.182, p = 0.019; OVERT, ß = 0.311, p = 0.009). Importantly, effect sizes of all three associations were more prominent in HT patients with prolonged and more severe disease (OVERT). Conclusion: Further research into the functional and causal relationships of the observed associations is important to provide guidance regarding coffee/sugar intake on vitamin D status. A well-balanced diet can help prevent vitamin D deficiency and improve the quality of life of patients with HT, especially those in later stages of disease characterized by greater metabolic imbalance.

Vitamin D and Hashimoto's Thyroiditis: Observations from CROHT Biobank.

The aims of this study were to evaluate: (1) associations of vitamin D with the presence/severity of Hashimoto's thyroiditis (HT) and (2) correlations of vitamin D with thyroid-related phenotypes. Total 25(OH)D (vitamin D in the text) was measured from stored serum samples of 461 HT patients and 176 controls from a Croatian Biobank of HT patients (CROHT). (1) Vitamin D levels, and proportions of vitamin D deficiency, were compared between HT cases and controls. HT patients were additionally divided into two groups (MILD and OVERT) to take into account HT severity. (2) Correlations between vitamin D and 10 clinical phenotypes in all HT patients and two subgroups of HT patients were tested using the Spearman correlation test. Our analyses were adjusted for age, gender, BMI, smoking status and seasonality of blood sampling. (1) No significant differences in vitamin D levels, or proportions of vitamin D deficiency, were detected between HT patients of all disease stages and controls. However, a nominally significant difference in vitamin D levels between MILD and OVERT subgroups (OR = 1.038, p = 0.023) was observed. Proportions of individuals with vitamin D deficiency during winter-spring were high: all HT cases (64.69%), MILD (60.64%), OVERT (68.7%), controls (60.79%). (2) A nominally significant negative correlation between vitamin D and TSH in all HT patients (r = -0.113, p = 0.029) and a positive correlation between vitamin D and systolic blood pressure in OVERT HT patients (r = 0.205, p = 0.025) were identified. Our study indicates that there is no association between vitamin D and HT; however, there may be a subtle decrease in vitamin D levels associated with overt hypothyroidism.

Shared genetic risk between eating disorder- and substance-use-related phenotypes: Evidence from genome-wide association studies.

Eating disorders and substance use disorders frequently co-occur. Twin studies reveal shared genetic variance between liabilities to eating disorders and substance use, with the strongest associations between symptoms of bulimia nervosa and problem alcohol use (genetic correlation [rg ], twin-based = 0.23-0.53). We estimated the genetic correlation between eating disorder and substance use and disorder phenotypes using data from genome-wide association studies (GWAS). Four eating disorder phenotypes (anorexia nervosa [AN], AN with binge eating, AN without binge eating, and a bulimia nervosa factor score), and eight substance-use-related phenotypes (drinks per week, alcohol use disorder [AUD], smoking initiation, current smoking, cigarettes per day, nicotine dependence, cannabis initiation, and cannabis use disorder) from eight studies were included. Significant genetic correlations were adjusted for variants associated with major depressive disorder and schizophrenia. Total study sample sizes per phenotype ranged from ~2400 to ~537 000 individuals. We used linkage disequilibrium score regression to calculate single nucleotide polymorphism-based genetic correlations between eating disorder- and substance-use-related phenotypes. Significant positive genetic associations emerged between AUD and AN (rg = 0.18; false discovery rate q = 0.0006), cannabis initiation and AN (rg = 0.23; q < 0.0001), and cannabis initiation and AN with binge eating (rg = 0.27; q = 0.0016). Conversely, significant negative genetic correlations were observed between three nondiagnostic smoking phenotypes (smoking initiation, current smoking, and cigarettes per day) and AN without binge eating (rgs = -0.19 to -0.23; qs < 0.04). The genetic correlation between AUD and AN was no longer significant after co-varying for major depressive disorder loci. The patterns of association between eating disorder- and substance-use-related phenotypes highlights the potentially complex and substance-specific relationships among these behaviors.

Thyroid hormone levels are associated with metabolic components: a cross-sectional study.

AIM: To analyze the association of thyroid function and hormone levels with metabolic syndrome (MetS) and its components. METHODS: This cross-sectional population-based study involved 2183 Croatian individuals with no history of thyroid disease, hypertension, diabetes, and hyperlipidemia. MetS was diagnosed according to the National Cholesterol Education Program's Adult Treatment Panel III criteria. RESULTS: We found no association between thyroid function groups and the prevalence of MetS and its components. Clinically hypothyroid participants showed significantly higher triceps skinfold measurements than subclinically hypothyroid and euthyroid participants. Furthermore, clinically hypothyroid participants had higher abdominal skinfold thickness than subclinically hypothyroid participants. Otherwise, suprailiac and abdominal skinfold measurements were higher in the subclinically and clinically hyperthyroid group of participants compared with euthyroid and subclinically hypothyroid participants. A strong positive association of thyroid-stimulating hormone (TSH) and strong negative association of free triiodothyronine (fT3) and free thyroxine (fT4) levels with HOMA-IR and cholesterol levels were found. Furthermore, the fT4 level also showed a strong negative association with HDL and triceps skinfold thickness. CONCLUSIONS: This study supports the standing that TSH, fT3, and fT4 levels are important variables to determine the association of thyroid function with MetS.

Differences in food consumption between patients with Hashimoto's thyroiditis and healthy individuals.

Food is considered as important environmental factor that plays a role in development of Hashimoto's thyroiditis (HT). The goal of our study was to identify food groups, assessed by food frequency questionnaire, that differ in consumption frequency between 491 patients with HT and 433 controls. We also analysed association of food groups with the wealth of HT-related clinical traits and symptoms. We found significantly increased consumption of animal fat (OR 1.55, p < 0.0001) and processed meat (OR 1.16, p = 0.0012) in HT cases, whereas controls consumed significantly more frequently red meat (OR 0.80, p < 0.0001), non-alcoholic beverages (OR 0.82, p < 0.0001), whole grains (OR 0.82, p < 0.0001) and plant oil (OR 0.87, p < 0.0001). We also observed association of plant oil consumption with increased triiodothyronine levels in HT patients (ß = 0.07, p < 0.0001), and, association of olive oil consumption with decreased systolic blood pressure (ß = - 0.16, p = 0.001) in HT patients on levothyroxine (LT4) therapy. Analysis of food consumption between HT patients with and without LT4 therapy suggest that patients do not tend to modify their diet upon HT diagnosis in our population. Our study may be of relevance to nutritionists, nutritional therapists and clinicians involved in developing dietary recommendations for HT patients.

AATF and SMARCA2 are associated with thyroid volume in Hashimoto's thyroiditis patients.

Thyroid volume of Hashimoto's thyroiditis (HT) patients varies in size over the course of disease and it may reflect changes in biological function of thyroid gland. Patients with subclinical hypothyroidism predominantly have increased thyroid volume whereas patients with more pronounced hypothyroidism have smaller thyroid volumes. Suggested mechanism for thyroid atrophy is thyrocyte death due to apoptosis. We performed the first genome-wide association study (GWAS) of thyroid volume in two groups of HT patients, depending on levothyroxine (LT4) therapy, and then meta-analysed across. Study included 345 HT patients in total and 6 007 322 common autosomal genetic variants. Underlying hypothesis was that genetic components that are involved in regulation of thyroid volume display their effect in specific pathophysiologic conditions of thyroid gland of HT patients. We additionally performed immunohistochemical analysis using thyroid tissues and analysed differences in expression levels of identified proteins and apoptotic marker between HT patients and controls. We found genome-wide significant association of two loci, both involved in apoptosis, with thyroid volume of HT patients: rs7212416 inside apoptosis-antagonizing transcription factor AATF (P = 8.95 × 10-9) and rs10738556 near chromatin-remodeling SMARCA2 (P = 2.83 × 10-8). In immunohistochemical analysis we observed that HT patients with homozygous AATF risk genotypes have decreased AATF expression (0.46-fold, P < 0.0001) and increased apoptosis (3.99-fold, P = 0.0001) in comparison to controls. HT patients with heterozygous SMARCA2 genotypes have decreased SMARCA2 expression, albeit without reaching statistical significance (1.07-fold, P = 0.5876), and significantly increased apoptosis (4.11-fold, P < 0.0001). By two lines of evidence we show that two highly plausible genetic loci, AATF and SMARCA2, may be involved in determining the thyroid volume of HT patients. The results of our study significantly add to the current knowledge of disturbed biological mechanisms in thyroid gland of HT patients.

Genome-Wide Analysis Identifies Two Susceptibility Loci for Positive Thyroid Peroxidase and Thyroglobulin Antibodies.

INTRODUCTION: Thyroid peroxidase (TPO) and thyroglobulin (Tg) are main components of the thyroid gland and play an essential role in thyroid hormone synthesis. The development of antibodies to thyroid peroxidase (TPOAb) and thyroglobulin (TgAb) is the major diagnostic hallmark and early indicator of autoimmune thyroid disease. TPOAb and TgAb are under strong genetic influence; however, genetic factors that determine thyroid antibody positivity are largely unknown. MATERIALS AND METHODS: To identify novel loci associated with TPOAb and/or TgAb positivity, we performed a genome-wide meta-analysis in a total of 2613 individuals from Croatia. Participants with elevated plasma TPOAb and/or TgAb were defined as cases (N = 619) and those with TPOAb and TgAb within reference values were defined as controls (N = 1994). RESULTS: We identified 2 novel loci, of which 1 is located within the YES1 gene (rs77284350, P = 1.50 × 10-8), and the other resides within the IRF8 gene (rs16939945, P = 5.04 × 10-8). CONCLUSIONS: Although the observed variants were associated with TPOAb and TgAb positivity for the first time, both YES1 and IRF8 were previously linked to susceptibility to other autoimmune diseases, and represent plausible biological candidates. This study adds to the knowledge of genetics underlying thyroid antibodies and provides a good basis for further research.

Genetic Variants in the ST6GAL1 Gene Are Associated with Thyroglobulin Plasma Level in Healthy Individuals.

Background: Thyroglobulin (Tg) is a 660 kDa iodoglycoprotein that serves as a scaffold for thyroid hormone synthesis. Although a twin study showed that variability of serum Tg levels has a substantial genetic basis, no genome-wide association study (GWAS) of serum/plasma Tg levels has been performed to date. The aim of this study was to identify genetic variants associated with plasma Tg levels among healthy individuals. Methods: A GWAS was conducted on two Croatian cohorts, and a combined analysis was performed. The analyses included 1094 individuals. A total of 7,597,379 variants, imputed using the 1000 Genomes reference panel, were analyzed for association. GWAS was performed under an additive model, controlling for age, sex, and relatedness within each data set. Combined analysis was conducted using the inverse-variance fixed-effects method. Results: Sixteen variants located on chromosome 3, within the ST6GAL1 gene, reached genome-wide significance. The lead SNP was rs4012172 ( \documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\usepackage{upgreek}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document} $$p = 1.29 \times {10^{ - 10}}$$ \end{document} ), which explained 3.19% of the variance in Tg levels. ST6GAL1 belongs to the sialyltransferase protein family, which has a fundamental role in the synthesis of specific sialylated structures on various glycoproteins, including Tg. It is known that only immature Tg (poorly sialylated or desialylated) can be transferred to the bloodstream. Conclusions: A highly biologically plausible locus was identified that could have a role in the regulation of plasma Tg levels in healthy individuals.

Genome-wide association analysis suggests novel loci underlying thyroid antibodies in Hashimoto's thyroiditis.

Thyroid antibodies against thyroglobulin (TgAb) and thyroid peroxidase (TPOAb) are key markers of Hashimoto's thyroiditis (HT), the most common autoimmune thyroid disorder. Genetic determinants of thyroid antibodies are still poorly known, especially as they were not studied in patients with thyroid diseases. We performed the first genome-wide association analysis of thyroid antibodies in 430 HT patients that may be considered as population extremes for thyroid antibodies distribution. We detected two suggestively associated genetic variants with TgAb, rs6972286 close to ANKRD7 and LSM8 (P = 2.34 × 10-7) and rs756763 inside CA10 (P = 6.05 × 10-7), and one with TPOAb, rs12507813 positioned between TRIM61 and TRIM60 (P = 4.95 × 10-7). Bivariate analysis resulted with three suggestively associated genetic variants that predispose to both antibodies: rs13190616 inside RP11-138J23.1 (P = 2.01 × 10-6), rs561030786 close to DUBR (P = 7.33 × 10-6) and rs12713034 inside FSHR (P = 7.66 × 10-6). All identified genomic regions have a substantial literature record of involvement with female-related traits, immune-mediated diseases and personality traits that are all characterized by increased thyroid antibody levels. Our findings demonstrate the existence of genetic overlap between thyroid autoimmunity in HT and different non-thyroid diseases characterized by the presence of thyroid antibodies. We also suggest that genetic variants that regulate antibody levels may differ between HT patients and individuals with normal thyroid function.

Genome-wide association meta-analysis for total thyroid hormone levels in Croatian population.

Thyroid hormones (THs) are key regulators of cellular growth, development, and metabolism. The thyroid gland secretes two THs, thyroxine (T4) and triiodothyronine (T3), into the plasma where they are almost all bound reversibly to plasma proteins. Free forms of THs are metabolically active, however, they represent a very small fraction of total TH levels. No genome-wide studies have been performed to date on total TH levels, comprising of protein-bound and free forms of THs. To detect genetic variants associated with total TH levels, we carried out the first GWAS meta-analysis of total T4 levels in 1121 individuals from two Croatian cohorts (Split and Korcula). We also performed GWAS analyses of total T3 levels in 577 individuals and T3/T4 ratio in 571 individuals from the Split cohort. The top association in GWAS meta-analysis of total T4 was detected for an intronic variant within SLC22A9 gene (rs12282281, P = 4.00 × 10-7). Within the same region, a genome-wide significant variant (rs11822642, P = 2.50 × 10-8) for the T3/T4 ratio was identified. SLC22A9 encodes for an organic anion transporter protein expressed predominantly in the liver and belongs to the superfamily of solute carriers (SLC), a large group of transport membrane proteins. The transport of THs across the plasma membrane in peripheral tissues is facilitated by the membrane proteins, and all TH transport proteins known to date belong to the same SLC superfamily as SLC22A9. These results suggest a potential role for SLC22A9 as a novel transporter protein of THs.

The effect of multiple nutrients on plasma parathyroid hormone level in healthy individuals.

Although the effect of isolated nutrients on plasma parathyroid hormone (PTH) is somewhat familiar, the effect of multiple nutrients on plasma PTH level has not yet been studied. The aim of this study was to identify groups of food items that are associated with the plasma PTH level in healthy individuals. This cross-sectional study enrolled 1180 healthy individuals from Croatia with plasma PTH levels inside the referent values. A food frequency questionnaire containing 58 food items was completed to evaluate the dietary intake. We used principal component analysis to reduce food items into dietary groups, followed by linear regression analysis to test the association between dietary groups and the level of PTH. The results indicate that different sorts of vegetables (p = .006), sausages, salami, mushrooms, eggs (p = .033), as well as white bread (p = .009) are associated with the increase, while bran bread (p = .009) is associated with the decreased plasma PTH level.

Genome-wide meta-analysis identifies novel gender specific loci associated with thyroid antibodies level in Croatians.

Autoimmune thyroid diseases (AITD) are multifactorial endocrine diseases most frequently accompanied by Tg and TPO autoantibodies. Both antibodies have a higher prevalence in females and act under a strong genetic influence. To identify novel variants underlying thyroid antibody levels, we performed GWAS meta-analysis on the plasma levels of TgAb and TPOAb in three Croatian cohorts, as well as gender specific GWAS and a bivariate analysis. No significant association was detected with the level of TgAb and TPOAb in the meta-analysis of GWAS or bivariate results for all individuals. The bivariate analysis in females only revealed a genome-wide significant association for the locus near GRIN3A (rs4457391, P = 7.76 × 10-9). The same locus had borderline association with TPOAb levels in females (rs1935377, P = 8.58 × 10-8). In conclusion, we identified a novel gender specific locus associated with TgAb and TPOAb levels. Our findings provide a novel insight into genetic and gender differences associated with thyroid antibodies.

Thyroglobulin Antibodies are Associated with Symptom Burden in Patients with Hashimoto's Thyroiditis: A Cross-Sectional Study.

BACKGROUND: Hashimoto's thyroiditis (HT) is the most common form of autoimmune thyroid disorders characterized by lower production of thyroid hormones and positivity to autoantibodies to thyroglobulin (TgAb) and/or thyroid peroxidase (TPOAb). We performed a comprehensive phenotypic characterization of patients with HT, with specific focus on thyroid autoimmunity, to get better understanding of disease manifestation. METHODS: We collected information on thyroid-specific phenotypes (TSH, T3, T4, fT4, TgAb, TPOAb, thyroid volume) and other clinical phenotypes (age, body surface area, number of hypothyroidism symptoms, blood pressure) from 290 patients with HT without levothyroxine (LT4) therapy with the aim to test for correlations between thyroid-specific and clinical phenotypes. RESULTS: Our key and novel finding is the existence of significant positive correlation between TgAb levels and the number of symptoms (r = 0.25, p = 0.0001) in HT patients without LT4 therapy that remained significant after adjustment for TPOAb, T3, TSH levels and thyroid volume (ß = 0.66, SE = 0.3, p = 0.0299). Increased TgAb levels are significantly associated with fragile hair (p = 0.0043), face edema (p = 0.0061), edema of the eyes (p = 0.0293) and harsh voice (p = 0.0349). CONCLUSIONS: Elevated TgAb levels are associated with symptom burden in HT patients, suggesting a role of thyroid autoimmunity in clinical manifestations of HT. Based on these results, we recommend screening for TgAb antibodies in HT patients with symptom burden. We also suggest that further work on understandings of symptoms appearance due to their autoimmune or hypothyroid causation is needed.

Evaluation of Correlations Between Food-Specific Antibodies and Clinical Aspects of Hashimoto's Thyroiditis.

OBJECTIVE: We have comprehensively evaluated an immunologic response to food antigens, mediated by immunoglobulin G (IgG) antibodies, on clinical aspects of Hashimoto's thyroiditis (HT). METHODS: IgG antibodies to 125 food antigens were measured in serum samples of 74 HT patients and 245 controls using microarray-based enzyme-linked immunosorbent assay (ELISA) test. We analyzed differences in IgG levels between two groups and evaluated correlations between food-specific IgG levels and HT-related clinical phenotypes (thyroid hormones/antibodies, symptoms of hypothyroidism, measures of body size and blood pressure) and food consumption in HT patients. RESULTS: We observed increased IgG levels to 12 different food antigens in either HT cases or controls, of which plum-specific IgG antibodies were significantly higher (p = 1.70 × 10-8), and almond-specific IgG antibodies were significantly lower (p = 8.11 × 10-5) in HT patients in comparison to controls, suggesting their possible roles in HT etiology or symptomatology. There was no significant correlation between any of 12 increased food-specific IgG antibodies, along with gluten-specific IgG, with clinically important phenotypes, such as thyroid hormones/antibodies or symptoms. Among other tested correlations, the most interesting is the negative correlation between coffee and tea combined IgG levels and number of symptoms, suggesting possible beneficial effect of tea and coffee on disease symptoms. We also found that food consumption is not correlated with IgG levels. CONCLUSIONS: Distribution of food-specific IgG antibodies is comparable between HT patients and controls, with the exception of plum and almond. There is no evidence that increased food-specific IgG antibodies are associated with clinical aspects of HT. Clarification of biology behind formation of these antibodies is needed.

Genome-wide meta-analysis identifies novel loci associated with parathyroid hormone level.

BACKGROUND: Parathyroid hormone (PTH) is one of the principal regulators of calcium homeostasis. Although serum PTH level is mostly accounted by genetic factors, genetic background underlying PTH level is insufficiently known. Therefore, the aim of this study was to identify novel genetic variants associated with PTH levels. METHODS: We performed GWAS meta-analysis within two genetically isolated Croatian populations followed by replication analysis in a Croatian mainland population and we also combined results across all three analyzed populations. The analyses included 2596 individuals. A total of 7,411,206 variants, imputed using the 1000 Genomes reference panel, were analysed for the association. In addition, a sex-specific GWAS meta-analyses were performed. RESULTS: Polymorphisms with the lowest P-values were located on chromosome 4 approximately 84 kb of the 5' of RASGEF1B gene. The most significant SNP was rs11099476 (P = 1.15 × 10-8). Sex-specific analysis identified genome-wide significant association of the variant rs77178854, located within DPP10 gene in females only (P = 2.21 × 10- 9). There were no genome-wide significant findings in the meta-analysis of males. CONCLUSIONS: We identified two biologically plausible novel loci associated with PTH levels, providing us with further insights into the genetics of this complex trait.

Environmental Risk Factors for Type 1 Diabetes Mellitus Development.

Background Although environmental factors induce development of type 1 diabetes mellitus (T1DM) in genetically susceptible individuals, many of those factors have been uncovered. Therefore, the aim of the present study was to analyze associations of T1DM with a wide range of environmental factors. Material and Methods A case-control study was conducted on 249 diabetic and 255 healthy individuals from the Dalmatian region of South Croatia. Data regarding risk factors during pregnancy and early life period of the child were evaluated. Results History of antihypertensive intake (p=0.04) and frequency of stressful life events during pregnancy (p=0.01) were associated with higher risk of T1DM, while hypertension was associated with lower risk of T1DM (p=0.01). Maternal age<25 years at delivery was associated with a higher risk of T1DM (p=0.01).Diabetic patients had a positive family history of T1DM or T2DM (p=0.002) more frequently than controls, while history of infectious diseases was inversely associated with the risk of T1DM (p=0.03). A higher risk of T1DM was significantly associated with earlier introduction of cow's milk (p=0.001), higher number of meals consumed per day (p=0.02), higher frequency of carbohydrate (p=0.001) and meat (p=0.01) consumption and stressful life events during childhood (p=0.02) while earlier introduction of fruit was associated with a lower risk of T1DM (p=0.03) Conclusion This case-control study confirmed associations of a large number of environmental factors with development of T1DM with emphasis on the association of mother's antihypertensive intake during pregnancy, which extends our knowledge about environmental factors related with development of T1DM.

Association of Established Thyroid-stimulating Hormone and Free Thyroxine Genetic Variants with Hashimoto's Thyroiditis.

Hashimoto's thyroiditis (HT), the most frequent autoimmune thyroid disease (AITD), is characterized by chronic inflammation of the thyroid gland that usually results in hypothyroidism. Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels are used as clinical determinants of thyroid function. The main aim of this study was to explore the association of established TSH and FT4 genetic variants with HT. We performed a case-control analysis using 23 genetic markers in 200 HT patients and 304 controls. Additionally, we tested the association of selected variants with several thyroid-related quantitative traits in HT cases only. Two genetic variants showed nominal association with HT: rs11935941 near NR3C2 gene (p = 0.0034, OR = 0.57, 95% CI = 0.39-0.83) and rs1537424 near MBIP gene (p = 0.0169, OR = 0.72, 95% CI = 0.55-0.94). Additionally, three SNPs showed nominal association with thyroglobulin antibody (TgAb) levels: rs4804416 in INSR gene (p = 0.0073, ß = -0.51), rs6435953 near IGFBP5 gene (p = 0.0081, ß = 0.75), and rs1537424 near MBIP gene (p = 0.0117, ß = 0.49). GLIS3 genetic variant rs10974423 showed nominal association with thyroid peroxidase antibody (TPOAb) levels (p = 0.0465, ß = -0.56) and NRG1 genetic variant rs7825175 was nominally associated with thyroid gland volume (p = 0.0272, ß = -0.18). All detected loci were previously related to thyroid function or pathology. Findings from our study suggest biological relevance of NR3C2 and MBIP with HT, although these loci require additional confirmation in a larger replication study.

Association of established thyroid peroxidase autoantibody (TPOAb) genetic variants with Hashimoto's thyroiditis.

Hashimoto's thyroiditis (HT) is the most common form of autoimmune thyroid diseases (AITD) characterized by progressive destruction of thyroid tissue that may lead to hypothyroidism. High thyroid autoantibodies against thyroid peroxidase (TPOAb) levels are present in 90% of patients with HT and serve as a clinical marker for the detection of early AITD/HT. The main aim of our study was to test whether recently identified genetic variants associated with TPOAb are also involved in HT development. A total of 504 unrelated individuals, including 200 patients with HT and 304 controls, were involved in this study. Diagnosis of HT cases was based on clinical examination, measurement of thyroid hormones (TSH and fT4) and antibodies (TgAb, TPOAb) and ultrasound examination. We selected and genotyped 14 known TPOAb-associated genetic variants. Case-control logistic regression model was used to test the association of selected genetic variants with HT. Additionally, we tested association of the same genetic variants with thyroid related quantitative traits (TPOAb levels, TgAb levels and thyroid gland volume) using linear regression. Three genetic variants showed nominal association with HT; rs10774625 in ATXN2 gene (p = 0.0149, OR = 0.73, CI = 0.56-0.94), rs7171171 near RASGRP1 gene (p = 0.0356, OR = 1.4, CI = 1.02-1.92) and rs11675434 in TPO gene (p = 0.041, OR = 1.31, CI = 1.01-1.69). Two of these SNPs (rs1077462, rs11675434) also showed association with TPOAb levels (p = 0.043, ß = -0.39; p = 0.042, ß = 0.40, respectively) and one (rs7171171) was associated with thyroid gland volume (p = 0.0226, ß = -0.21). Our findings suggest that variants inside or near TPO, ATXN2 and RASGRP1 genes are associated with HT. Identified loci are novel to HT and represent good basis for further exploration of HT susceptibility.

Whole-exome sequencing in an isolated population from the Dalmatian island of Vis.

We have whole-exome sequenced 176 individuals from the isolated population of the island of Vis in Croatia in order to describe exonic variation architecture. We found 290 577 single nucleotide variants (SNVs), 65% of which are singletons, low frequency or rare variants. A total of 25 430 (9%) SNVs are novel, previously not catalogued in NHLBI GO Exome Sequencing Project, UK10K-Generation Scotland, 1000Genomes Project, ExAC or NCBI Reference Assembly dbSNP. The majority of these variants (76%) are singletons. Comparable to data obtained from UK10K-Generation Scotland that were sequenced and analysed using the same protocols, we detected an enrichment of potentially damaging variants (non-synonymous and loss-of-function) in the low frequency and common variant categories. On average 115 (range 93-140) genotypes with loss-of-function variants, 23 (15-34) of which were homozygous, were identified per person. The landscape of loss-of-function variants across an exome revealed that variants mainly accumulated in genes on the xenobiotic-related pathways, of which majority coded for enzymes. The frequency of loss-of-function variants was additionally increased in Vis runs of homozygosity regions where variants mainly affected signalling pathways. This work confirms the isolate status of Vis population by means of whole-exome sequence and reveals the pattern of loss-of-function mutations, which resembles the trails of adaptive evolution that were found in other species. By cataloguing the exomic variants and describing the allelic structure of the Vis population, this study will serve as a valuable resource for future genetic studies of human diseases, population genetics and evolution in this population.