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.

Objective: We evaluated correlations of occupational physical activity (OPA) and recreational exercise (RE), respectively, with thyroid function in patients with Hashimoto’s thyroiditis (HT). Methods: We included 438 individuals with clinically diagnosed HT. Information on OPA and RE were collected through a self-report questionnaire. We assessed correlations between clinical phenotypes (TSH, T3, T4, fT4, TgAb, TPOAb, thyroid volume, vitamin D) and physical activities (OPA and RE) in all HT patients (ALL) and in two severity-based subgroups of patients (MILD and OVERT). Results: The main novel findings are significant correlations between increase in OPA and (i) a decrease in fT4 (OVERT, r = −0.265, p = 0.0002 and ALL, r = −0.138, p = 0.006); (ii) an increase in TSH (ALL, r = 0.124, p = 0.014 and OVERT, r = 0.183, p = 0.013) and (iii) an increase in TPOAb antibodies (ALL, r = 0.101, p = 0.045). In contrast, we observed correlations between increase in RE and: (i) a decrease in TSH (OVERT, r = −0.238, p = 0.001); (ii) a decrease in TgAb antibodies (OVERT, r = −0.194, p = 0.01) and (iii) an increase in vitamin D levels (ALL, r = 0.146, p = 0.005 and OVERT, r = 0.173, p = 0.023). Conclusions: Our results suggest that, unlike RE, OPA correlates with decreased thyroid function and increased thyroid autoimmunity. Our study proposes that the PA health paradox also applies for the thyroid health.

Thyroid cancer is the predominant endocrine-related malignancy. ST6 β-galactoside α2,6-sialyltransferase 1 (ST6GAL1) has been studied in various types of cancers; however, the expression and function of ST6GAL1 in thyroid cancer has not been investigated so far. Previously, we conducted two genome-wide association studies and have identified the association of the ST6GAL1 gene with plasma thyroglobulin (Tg) levels. Since Tg levels are altered in thyroid pathologies, in the current study, we wanted to evaluate the expression of ST6GAL1 in thyroid cancer tissues. We performed an immunohistochemical analysis using human thyroid tissue from 89 patients and analyzed ST6GAL1 protein expression in papillary thyroid cancer (including follicular variant and microcarcinoma) and follicular thyroid cancer in comparison to normal thyroid tissue. Additionally, ST6GAL1 mRNA levels from The Cancer Genome Atlas (TCGA, n = 572) and the Genotype-Tissue Expression (GTEx) project (n = 279) were examined. The immunohistochemical analysis revealed higher ST6GAL1 protein expression in all thyroid tumors compared to normal thyroid tissue. TCGA data revealed increased ST6GAL1 mRNA levels in both primary and metastatic tumors versus controls. Notably, the follicular variant of papillary thyroid cancer exhibited significantly higher ST6GAL1 mRNA levels than classic papillary thyroid cancer. High ST6GAL1 mRNA levels significantly correlated with lymph node metastasis status, clinical stage, and reduced survival rate. ST6GAL1 emerges as a potential cancer-associated glycosyltransferase in thyroid malignancies, offering valuable insights into its diagnostic and prognostic significance.

Background: Hashimoto’s thyroiditis (HT) is a chronic autoimmune disease of the thyroid gland and is also the main cause of hypothyroidism. A recent genome-wide association study (GWAS) suggested an association of three novel genetic variants with HT in a population of Caucasian origin (Croatian). A case-control study was performed to investigate the association of these three newly suggested genetic variants with HT in a non-Caucasian ethnic group, an Arab-Berber from Algeria. Three variants (rs12944194 located 206 kb from SDK2, rs791903 inside IP6K3, and rs75201096 inside GNA14) were genotyped using real-time PCR. Results: There were no significant differences in allele frequencies of the three genetic variants between HT cases and controls. However, the present study showed nominal significance in the genotype distribution of rs791903 (IP6K3 gene) between HT patients and the control group (P = 0.024); we observed a decrease in the frequency of rs791903 recessive homozygotes (CC) in HT cases versus controls (OR = 0.476, P = 0.025). Conclusion: This is the first study that showed the genotypic association of IP6K3 intronic variant with decreased risk for HT in non-Caucasian, Algerian, population, whereas we did not confirm the association of SDK2 and GNA14 genetic variants with HT. The IP6K3 gene (inositol hexaphosphate kinase 3), located near major histocompatibility complex (MHC), has previously been associated with other common autoimmune diseases beside HT, such as Graves’s disease and rheumatoid arthritis, which is providing more evidence of a good candidacy for the genetic contribution to the development of HT and autoimmunity.

Background: Hashimoto's thyroiditis (HT) is the most common form of autoimmune thyroid disease which leads, in most cases, to hypothyroidism. HT is also classified as a multifactorial disease, which is caused by an interaction between genetic and environmental factors. Current knowledge of HT genetics is still very limited, especially in Algerian population. Objective: We wanted to investigate the association of two single-nucleotide polymorphisms (SNPs) inside VAV3 and SEPS genes with HT in Algerian population. Methods: We conducted a case-control study that included 100 HT cases and 126 healthy controls that were recruited from three private endocrinology clinics. Two SNPs, rs7537605 and rs28665122 inside VAV3 and SEPS genes were genotyped using real-time polymerase chain reaction (real-time PCR). Binary logistic regression model was used to test the association of selected SNs with HT and linear regression model was used to test association of these SNPs with thyroid peroxidase antibodies (TPOAb) levels. Results: Binary logistic regression results revealed no allelic association of the minor allele A between Hashimoto's thyroiditis cases and healthy controls (P=0.896) for the rs7537606 in VAV3 gene. The same observation was reported for the AA (P=0.477), AG (P=0.752) genotypes and for the genotypic models: dominant (P=1.0) and recessive (P=0.555). Also, there was no significant difference in the TT (P=0.230), TC (P=0.717) and allelic distribution of the minor allele T (P=0.859), and the combined models: TT + TC (P=1.0), TC + CC (P=0.138) between patients and controls for the rs28665122 polymorphism of the SEPS1 gene. Conclusion: This is the first genetic study that investigated the genetic association of rs7537605 and rs28665122 inside VAV3 and SEPS genes in Algerian population. Our results suggest that these two SNPs may not be involved in the pathogeneses of HT since we found no association between them and HT/TPOAb levels. Further research that will include larger sample size is required. Keywords: Hashimoto’s thyroiditis; inflammation; hypothyroidism; rs7537605; rs28665122; Algerian population.

Background/Objectives: Vitamin D is an important regulator of immune and inflammatory processes, while its deficiency is frequently observed in Hashimoto’s thyroiditis (HT). The relationship between Vitamin D and systemic inflammation in HT remains insufficiently understood, particularly across different disease stages. Methods: We used the Olink Target 96 Inflammation panel to investigate this association. Inflammatory proteins and serum 25(OH)D levels were measured in 257 HT patients and 173 controls from the CROHT biobank. Participants were categorized as Vitamin D deficient (<20 ng/mL) or non-deficient (≥20 ng/mL), with HT patients further stratified as euthyroid, hypothyroid, or levothyroxine-treated. Associations between 25(OH)D and 92 inflammatory proteins were assessed using multivariable linear regression adjusted for age, sex, BMI, smoking, and season of blood sampling, followed by interaction testing and meta-analysis. Results: Vitamin D deficiency was prevalent in both HT patients and controls. Among Vitamin D-deficient HT patients, higher 25(OH)D levels showed nominal inverse associations with the previously reported HT-associated inflammatory proteins IL-17C, CCL20, and CCL11, as well as with GDNF. Among non-deficient HT patients, a nominal positive association with CD6 was observed. None of these associations or interaction terms remained statistically significant after false discovery rate correction. Conclusions: These findings should therefore be considered exploratory and hypothesis-generating. Nevertheless, the observed Vitamin D status-specific patterns suggest that the relationship with inflammatory profiles in HT may differ according to Vitamin D status and warrant validation in prospective and mechanistic studies.