Background: Defects in thyroid hormone synthesis at birth lead to congenital hypothyroidism (CH). Recently, pathogenic variants in the SLC26A7 gene have been linked to dyshormonogenetic goitrous CH. This anion transporter is highly expressed in the thyroid and is involved in thyroid hormone synthesis; however, its exact function and cellular localization remain unclear. In this study, we investigated SLC26A7 variants in Finnish patients with CH, characterized the phenotypes, and analyzed thyroid-specific gene expression.Methods: SLC26A7 variants were identified from a clinical CH cohort (n = 139) using exome sequencing, and the FinnGen database (R12 release) was screened for disease associations. Thyroid histology and thyroid-specific gene expression were analyzed in six human samples (including two homozygous SLC26A7 pathogenic variant carriers, patients with goitrous and hyperactive thyroids, and normal controls) and in thyroids from different mouse models (including hypo- and hyperthyroid mice, thyroid-specific G-protein deficient, and Slc26a7-knockout mice).Results: Four CH patients from four novel families carried the homozygous SLC26A7 (c.1893delT, p.F631Lfs*8) pathogenic variant. Two had large trachea-compressing goiters, requiring thyroidectomy already at birth. In addition, one homozygous participant with normal CH screening results developed hypothyroidism at age 16, and one patient with heterozygous SLC26A7 pathogenic variant had permanent CH at birth. Dentofacial abnormalities were frequently noted, including enamel hypoplasia (in four carriers), pro- or retrognathia, and malocclusion requiring orthodontic treatment (in 8/24 carriers). Thyrocyte hypertrophy with large colloid aggregates was a hallmark of homozygous patients. FinnGen screening revealed a 75-fold enrichment of the variant in the Finnish population, identifying a few other homozygous and seven heterozygous cases with early-onset hypothyroidism and dentofacial abnormalities. In human thyrocytes, SLC26A7 was localized to the basolateral membrane, with intense staining in hyperthyroid samples, while in mouse thyroid models, its expression pattern depended on dietary iodide levels, thyrotropin signaling, and GNAS activity.Conclusions: We describe variable phenotypes associated with the SLC26A7 pathogenic variant, ranging from severe CH with large congenital goiters to delayed onset hypothyroidism and dentofacial abnormalities. SLC26A7 shows thyrotropin-, GNAS-, and dietary iodine-dependent basolateral localization, suggesting their role in phenotypic variations.

The high prevalence (>5%) of autoimmune hypothyroidism (AIHT) provides a unique opportunity to dissect genetic contributions to systemic and organ-specific autoimmunity. Here we performed a genome-wide association meta-analysis of 81,718 AIHT cases in FinnGen and the UK Biobank, identifying 418 independent signals (P < 5 × 10-8). At 48 of these loci, a protein-coding variant is, or is highly correlated (r2 > 0.95) with, the lead variant, including Finnish-enriched coding variants in LAG3, ZAP70 and TG. We demonstrated that ZAP70:T155M reduces T cell activation and broadly compare large-scale scans of nonthyroid autoimmunity and thyroid-stimulating hormone levels with a Bayesian classifier to assign loci into distinct groupings, estimating that 38% are involved in general autoimmunity whereas 20% are thyroid specific. We further identified substantial antagonistic pleiotropy, with 10% of AIHT loci showing a consistent protective effect against skin cancer. The AIHT results, including numerous genes encoding checkpoint proteins, support the causal role of natural immune variation influencing cancer outcomes.

CONTEXT:Autoimmune destruction of β cells and their functional decline precedes the clinical onset of type 1 diabetes. However, altered α-cell function and hyperglucagonemia may contribute to the development of hyperglycemia and ketoacidosis at onset. OBJECTIVE:In this cross-sectional study, we analyzed glucagon concentrations during an oral glucose tolerance test (OGTT) in individuals at the early stages of type 1 diabetes to understand the role of α-cell function in the disease process. METHODS:We recruited 47 participants, aged 4 to 25 years, from the Finnish Diabetes Prediction and Prevention (DIPP) study, and categorized them into the following groups: islet autoantibody (IAb) negative, single IAb positive, and stages 1 to 3 of type 1 diabetes. Glucagon levels were measured during a 6-point OGTT using a conventional radioimmunoassay, alongside insulin, C-peptide, glucose, and glucagon-like peptide-1 (GLP-1). RESULTS:Fasting plasma glucagon levels increased with disease progression. The longitudinal patterns of glucagon concentrations during the OGTT differed significantly between groups, with a paradoxical 15-minute glucagon increase observed only in individuals at early stage 3 of type 1 diabetes. CONCLUSION:These findings highlight the need for prospective studies to further elucidate the role of α cells in disease progression and support testing pharmacotherapies aimed at improving both α- and β-cell functions during disease development.

Background: Constitutively active mutations (CAMs) in the thyrotropin receptor (TSHR) are the major cause of nonautoimmune hyperthyroidism. TSHR is a key regulator of thyroid hormone synthesis, which is essential for skeletal formation, bone turnover, and craniofacial development. In addition to its role in thyroid hormone regulation, thyrotropin and its receptor have been proposed to independently influence bone formation and resorption. However, the specific effects of constitutively active TSHR mutations on cranial and skeletal development have not been investigated in mouse models. Methods: Cranial morphometry, micro-computed tomography, and three-point bending tests were performed in established TSHR knock-in mouse models carrying patient-derived TSHR D633H or M453T CAMs. Homozygous TSHR D633H mice exhibit mild, transient hyperthyroidism at 2 months of age, more pronounced in females, whereas homozygous TSHR M453T mice develop a more severe, iodine-dependent hyperthyroid phenotype. Results: Both TSHR CAM lines showed altered craniofacial morphology, particularly in nasal bone dimensions, resulting in a shorter snout compared with wild-type (WT) controls. The incidence of malocclusion was significantly increased in both homozygous and heterozygous mice, regardless of sex. TSHR D633H mice displayed no significant changes in femoral or tibial bone structure or biomechanical properties. In contrast, TSHR M453T mice exhibited hyperthyroidism-dependent alterations in trabecular bone mineral density (BMD) and architecture, while cortical bone was unaffected. Body and tail lengths were unchanged in TSHR D633H mice. M453T homozygous mice had reduced tail length at weaning in an iodine-dependent manner, which normalized with age. Conclusions: This in vivo study demonstrates that TSHR CAM-induced hyperthyroidism alters craniofacial morphology and increases the incidence of malocclusion in mice. Structural changes and altered BMD in M453T mice were dependent on the severity of hyperthyroidism. These findings highlight the role of TSHR signaling and thyroid status in craniofacial and skeletal development, warranting further mechanistic investigation.

Beyond well-known genetic drivers, microRNA dysregulation has emerged as a key contributor to thyroid tumorigenesis. Central to this process is Dicer1, a ribonuclease essential for microRNA maturation, whose expression is often reduced in papillary thyroid carcinoma (PTC). Evidence from previous studies suggest Dicer1 functions as a context-dependent haplo-insufficient tumor suppressor gene: partial loss may promote tumor development, whereas complete loss may disrupt essential cellular functions, causing cell death and tumor suppression. However, the effects of partial or complete Dicer1 loss in thyroid cancer remain unclear. To explore this, we genetically inactivated one (heterozygous) or both (homozygous) Dicer1 alleles specifically in thyroid follicular cells of a RET/PTC3 transgenic mouse model using an inducible Cre-Lox system. Our findings deepen the current understanding of the RET/PTC3-driven PTC model by revealing an increased number of vimentin-positive cells and disruption in redox homeostasis. Additionally, whereas heterozygous Dicer1 loss did not alter tumor progression in RET/PTC3 mice, total loss reduced tumor growth and led to accumulated DNA damage and cell death. These findings highlight the crucial role of Dicer1 dosage in thyroid cancer progression and underscore its potential as a therapeutic target for aggressive PTC and other malignancies characterized by aberrant Dicer1 expression.

Background: Under sufficient iodine supply, dual oxidase (DUOX)-dependent H2O2 production constitutes the limiting factor for thyroid hormone (TH) synthesis. Inherited loss-of-function mutations in related genes can trigger congenital hypothyroidism (CH). TH supplementation is not always well-tolerated and requires dose adjustments throughout life. Regenerative medicine directed at thyroid follicular cells (TFCs) could offer an alternative therapy; however, the minimal number of TFCs to be corrected remains unknown. Methods: Thyroid dyshormonogenesis in Duoxa-/- deficient mice was rescued by conditional thyroid-specific expression of DUOXA2/DUOX2 subunits. In order to restrict reactivation in a subset of TFCs, low doses of tamoxifen (0.1-2 mg) were injected. Thyroid function was assessed by immunostaining of iodinated-thyroglobulin (iTG). Circulating serum thyrotropin (TSH) and total thyroxin (T4) were quantified, and thyroidal expression of TSH-responsive genes (Nis, Tpo, Tshr) and hepatic deiodinase type-1 (Dio1) was measured. Last, combining iTG immunostaining with Duox2 in situ hybridization, we estimated the fraction of rescued TFCs required to restore follicular TG iodination. Results: Colloidal iTG+ staining in more than 90% of follicles demonstrated the successful rescue of TH biogenesis in doxycycline-induced Tet:Da2D2+/-;mTg:CreERT2+/-;Duoxa-/- animals (3TA). In contrast, reducing tamoxifen doses to 0.1 mg resulted in unresolved primary CH with thyroid enlargement, induction of Nis, Tpo, and Tshr, decrease of Dio1, and growth delay. Corresponding thyroid sections revealed scattered iTG+ colloidal lumens dispersed in histologically altered parenchyma. Nevertheless, we determined that only 11-15% of TFCs need to be reactivated within the follicle to functionally restore iodide organification. Goiter involution was also studied in 3TA following functional oxidase recovery or levothyroxine supplementation. Although thyroid enlargement was similarly reduced in both groups, expression of Nis, Tpo, Tshr, and Dio1 more rapidly normalized in genetically rescued 3TA. In these pathological conditions, around 50-70% of iTG+ follicles would seem sufficient to recover a healthy thyroid function until two weeks. Conclusions: Our data in Duoxa-/- mice suggest that the percentage of TFCs to be corrected is limited to 10-15% per follicle, which could be compatible with future somatic gene therapies. Furthermore, the reconstitution of hormonogenic-competent TFCs successfully results in goiter resolution, to an extent comparable to that of gold-standard TH replacement therapy.

Purpose:A randomized clinical trial was conducted to evaluate the impact of a gluten-free diet (GFD) on β-cell function and glucose tolerance in persons with multiple islet autoantibodies. Methods:Individuals (n = 59; median age 11 years) with multiple islet autoantibodies were recruited to a randomized clinical trial between April 2016 and April 2021. The participants were randomized to a GFD (n = 30; female n = 14) or a normal diet (ND) (n = 29; female n = 16). The study was conducted at 6 clinical research centers in Finland and Sweden, with a dietary intervention for 17 months followed by a 6-month washout on a ND. The primary outcomes were (1) the proportion of participants going from normal glucose tolerance at the time of the randomization to abnormal glucose tolerance by 18 months, (2) a change in first-phase insulin response in IV glucose tolerance tests between randomization and 18 months, and (3) a change in C-peptide area under the curve in oral glucose tolerance test between randomization and 18 months. Results:We did not find differences between participants randomized to GFD and ND in any of the glucose tolerance outcomes. No serious adverse events or adverse events related to a GFD were noted. Conclusion:Being on a GFD was not found to differ from being on a ND in preserving β-cell function or maintaining normal glucose tolerance in persons with multiple islet autoantibodies.

Autoimmune hypothyroidism occurs rarely before 3 years of age. Two siblings were diagnosed with autoimmune hypothyroidism at age 5 and 16 months, presenting with classic symptoms of hypothyroidism, abnormal thyroid function tests (TSH: 200 and 660 mU/L; reference range (RR): 0.73–8.4 mU/L; Free T4: 5.9 and <1.3 pmol/L; RR: 11.9–25.6 pmol/L), and high thyroid peroxidase antibody levels. Thyroxine medication alleviated their symptoms. Apart from mild infections, the siblings exhibited no other major disorders. Whole exome sequencing identified a pathogenic STAT3 gain-of-function variant, most commonly associated with infantile-onset multi-organ autoimmune disorder. Genetic testing for early-onset hypothyroidism may reveal specific etiologies, impacting follow-up and treatment.

BACKGROUND:Anaplastic thyroid cancer (ATC) is the most aggressive thyroid cancer with a median survival of less than six months. So far, no therapies offering a survival benefit are established. Thus, new therapeutic approaches are urgently needed. In general, genetic alterations leading to ATC increase PI3K and MAPK/ERK signaling and include mutations in receptor tyrosine kinases and tumor suppressor genes. They often occur together with the loss of p53, the most prevalent mutation in human ATC. Among such alterations are mutations and rearrangements of the anaplastic lymphoma kinase (ALK) gene. METHODS:To study ATC and potential treatment options, we generated a mouse model with inducible thyrocyte-specific expression of constitutively active mutant ALKF1174L and homozygous deletion of Trp53 due to a Cre recombinase under control of the thyroglobulin promoter (thyroglobulin [Tg]-CreERT2+/0;lox-stop-lox (LSL)-ALKF1174L/+;Trp53LoxP/LoxP mice, here referred to as Trp53KO/ALKF1174L mice). Moreover, we established several primary thyroid cancer cell lines harboring ALKF1174L and Trp53KO and investigated the effects of ALK inhibition in vitro and in vivo. RESULTS:Median survival of Trp53KO/ALKF1174L mice was severely reduced, and the mice showed massively enlarged thyroids. Histopathology confirmed the development of locally invasive and metastatic ATC. Treatment of primary Trp53KO/ALKF1174L ATC cells with the ALK inhibitor TAE-684 decreased AKT and ERK phosphorylation and induced a dose-dependent cytotoxicity. Trp53KO/ALKF1174L mice treated with TAE-684 showed significantly extended median survival compared with the solvent group (66 days vs. 18 days, p < 0.0001). CONCLUSIONS:Our data demonstrate that the combination of ALKF1174L mutation with Trp53 loss leads to the development of ATC. This study provides the first functional data supporting the use of ALK inhibitors in patients with ALK-driven ATC. Our novel ATC mouse model and the derived cell lines offer valuable tools to explore the molecular characteristics of ATC, especially signaling pathway activation and tumor microenvironment, and to test novel therapeutics for the treatment of advanced thyroid cancers.

The high prevalence of autoimmune hypothyroidism (AIHT) - more than 5% in human populations - provides a unique opportunity to unlock the most complete picture to date of genetic loci that underlie systemic and organ-specific autoimmunity. Using a meta-analysis of 81,718 AIHT cases in FinnGen and the UK Biobank, we dissect associations along axes of thyroid dysfunction and autoimmunity. This largest-to-date scan of hypothyroidism identifies 418 independent associations (p < 5×10- 8), more than half of which have not previously been documented in thyroid disease. In 48 of these, a protein-coding variant is the lead SNP or is highly correlated (r2 > 0.95) with the lead SNP at the locus, including low-frequency coding variants at LAG3, ZAP70, TG, TNFSF11, IRF3, S1PR4, HABP2, ZNF429 as well as established variants at ADCY7, IFIH1 and TYK2. The variants at LAG3 (P67T), ZAP70 (T155M), and TG (Q655X) are highly enriched in Finland and functional experiments in T-cells demonstrate that the ZAP70:T155M allele reduces T-cell activation. By employing a large-scale scan of non-thyroid autoimmunity and a published meta-analysis of TSH levels, we use a Bayesian classifier to dissect the associated loci into distinct groupings and from this estimate, a significant proportion are involved in systemic (i.e., general to multiple autoimmune conditions) autoimmunity (34%) and another subset in thyroid-specific dysfunction (17%). By comparing these association results further to other common disease endpoints, we identify a noteworthy overlap with skin cancer, with 10% of AIHT loci showing a consistent but opposite pattern of association where alleles that increase the risk of hypothyroidism have protective effects for skin cancer. The association results, including genes encoding checkpoint inhibitors and other genes affecting protein levels of PD1, bolster the causal role of natural variation in autoimmunity influencing cancer outcomes.

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

AIM:This study aimed to assess the cognitive development of individuals with congenital hypothyroidism. METHODS:Using hospital records, we identified 180 patients with congenital hypothyroidism born between 1980 and 2018 in Turku and Kuopio University Hospital catchment areas. Cognitive development was evaluated in 22 adults (7 males and 15 females) and 20 children (8 males and 12 females) using age-specific Wechsler Intelligence Scales. Full-scale IQ (FSIQ) and the four indices were compared to standardisation samples. Simple linear regression was used to test whether treatment-related variables predicted FSIQ. RESULTS:FSIQ and its four indices differed significantly from the standardisation sample in adults with congenital hypothyroidism (FSIQ 87.64, SD 13.70, p < 0.001) but not in children (FSIQ 97.90, SD 15.12). Adults had received a lower initial levothyroxine dose than children (8.1 mg/kg, 95% CI 7.2-9.0 vs. 10.2 mg/kg 9.7-10.7, p < 0.001), and their treatment was initiated later (4.8 days, 95% CI 4.0-5.6 vs. 3.6 days, 2.9-4.2, p = 0.018). CONCLUSION:Adults with congenital hypothyroidism had a significantly lower FSIQ compared to the population standard, while children's FSIQ did not differ. Our findings suggest that a higher initial levothyroxine dose together with very early treatment start may lead to better cognitive outcomes.

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

The clinical spectrum of thyrotropin receptor-mediated (TSHR-mediated) diseases varies from loss-of-function mutations causing congenital hypothyroidism to constitutively active mutations (CAMs) leading to nonautoimmune hyperthyroidism (NAH). Variation at the TSHR locus has also been associated with altered lipid and bone metabolism and autoimmune thyroid diseases. However, the extrathyroidal roles of TSHR and the mechanisms underlying phenotypic variability among TSHR-mediated diseases remain unclear. Here we identified and characterized TSHR variants and factors involved in phenotypic variability in different patient cohorts, the FinnGen database, and a mouse model. TSHR CAMs were found in all 16 patients with NAH, with 1 CAM in an unexpected location in the extracellular leucine-rich repeat domain (p.S237N) and another in the transmembrane domain (p.I640V) in 2 families with distinct hyperthyroid phenotypes. In addition, screening of the FinnGen database revealed rare functional variants as well as distinct common noncoding TSHR SNPs significantly associated with thyroid phenotypes, but there was no other significant association between TSHR variants and more than 2,000 nonthyroid disease endpoints. Finally, our TSHR M453T-knockin model revealed that the phenotype was dependent on the mutation's signaling properties and was ameliorated by increased iodine intake. In summary, our data show that TSHR-mediated disease risk can be modified by variants at the TSHR locus both inside and outside the coding region as well as by altered TSHR-signaling and dietary iodine, supporting the need for personalized treatment strategies.

Background: Gluten-free diet (GFD) has been advocated to preserve glucose metabolism and beta-cell function in newly diagnosed stage 3 type 1 diabetes. There is a gap in knowledge if GFD affect b-cell function or glucose metabolism in individuals with two or more islet autoantibodies with normoglycemic stage 1 or abnormal glucose tolerance stage 2 type 1 diabetes. A community-based, randomised, controlled open-label superiority trial was therefore conducted at six sites in Finland and Sweden.Methods: A total of 59 individuals, 2-49·99 years of age, in stage 1 or stage 2 type 1 diabetes were randomised to either GFD (n=30) or normal diet (ND, n=29) followed by 6-month washout on ND. Primary outcomes were 1) proportion of participants changing from normal glucose tolerance (NGT) at baseline to abnormal glucose tolerance (AGT) in serial oral glucose tolerance tests (OGTT); 2) mean difference in change in first-phase insulin response (FPIR) between baseline and 17 months in serial intravenous glucose tolerance tests (IVGTT), and 3) mean difference in change in C-peptide area under the curve in serial OGTT between baseline and 17 months on GFD. This study was registered with ClinicalTrials.gov number NCT02605148. Findings: Individuals were recruited between April 2016 and April 2020 and thirty participants (female n=14) were randomised to GFD and 29 (female n=16) to ND. Thirteen participants (7 in GFD and 6 in ND) developed stage 3 type 1 diabetes and six participants dropped out from the study. There was no differences between participants randomised to GFD and ND in the three primary outcomes. No serious adverse events or adverse events causally related to GFD were noted.Interpretation: GFD was not superior to ND in preserving b-cell function and normal glucose tolerance in individuals with stage 1 and stage 2 type 1 diabetes.Funding: Funded by JDRF International (grant 2-SRA-2014-309-M-R), the Swedish Foundation for Strategic Research (Dnr IRC15-0067), the Swedish Research Council, Strategic Research Area (Dnr 2009-1039), and Special Research Funds for University Hospitals in Finland.Declaration of Interest: None to declare. Ethical Approval: The study was approved by the Regional Ethical Committee in Lund as well as by the Swedish Ethical Review Authority and by the Ethics Committee of the Hospital District of Southwest Finland in Turku, Finland.

Objective: Nonautoimmune hyperthyroidism (NAH) is rare and occurs due to a constitutively activating thyroid stimulating hormone receptor (TSHR) mutation. In contrast to other thyroid nodules, no further evaluation for malignancy is recommended for hot thyroid nodules. In the first model for NAH in mice nearly all homozygous mice had developed papillary thyroid cancer by 12 months of age. Methods: To further evaluate these mice, whole exome sequencing and phosphoproteome analysis were employed in a further generation of mice to identify any other mutations potentially responsible and to identify the pathways involved in thyroid carcinoma development. Results: Only three genes (Nrg1, Rrs1, Rasal2) were mutated in all mice examined, none of which were known primary drivers of papillary thyroid cancer development. Wild-type and homozygous TSHR D633H knockin mice showed distinct phosphoproteome profiles with an enrichment of altered phosphosites found in ERK/mitogen-activated protein kinase (MAPK) signaling. Most importantly, phosphosites with known downstream effects included BRAF p.S766, which forms an inhibitory site: a decrease of phosphorylation at this site suggests an increase in MEK/ERK pathway activation. The decreased phosphorylation at BRAF p.S766 would suggest decreased AMP-activated protein kinase (AMPK) signaling, which is supported by the decreased phosphorylation of STIM1 p.S257, a downstream AMPK target. Conclusion: The modified phosphoproteome profile of the homozygous mice in combination with human literature suggests a potential signaling pathway from constitutive TSHR signaling and cAMP activation to the activation of ERK/MAPK signaling. This is the first time that a specific mechanism has been identified for a possible involvement of TSH signaling in thyroid carcinoma development.

CONTEXT:Patients with congenital hypothyroidism (CH) are affected more often than the general population by other chronic diseases and neurological difficulties. OBJECTIVE:The aim of this nationwide population-based register study was to investigate the incidence of congenital malformations, comorbidities, and the use of prescribed drugs in patients with primary CH. METHODS:The study cohort and matched controls were identified from national population-based registers in Finland. All diagnoses from birth until the end of 2018 were collected from the Care Register, and subject-specific prescription drug purchases were identified from The Prescription Register from birth until the end of 2017. RESULTS:Diagnoses of neonatal and chronic diseases were collected for 438 full-term patients and 835 controls (median follow-up time 11.6 years; range, 0-23 years). Newborns with CH were more often found to have neonatal jaundice (11.2% and 2.0%; P < .001), hypoglycemia (8.9% and 2.8%; P < .001), metabolic acidemia (3.2% and 1.1%; P = .007), and respiratory distress (3.9% and 1.3%; P < .003) as compared to their matched controls.Congenital malformations were diagnosed in 66 of 438 (15.1%) CH patients and in 62 of 835 (7.4%) controls (P < .001). The most commonly affected extrathyroidal systems were the circulatory and musculoskeletal systems. The cumulative incidence of hearing loss and specific developmental disorders was higher among CH patients than controls. The use of antidepressant and antipsychotic drugs was similar in CH patients and their controls. CONCLUSION:CH patients have more neonatal morbidity and congenital malformations than their matched controls. The cumulative incidence of neurological disorders is higher in CH patients. However, our results do not support the existence of severe psychiatric comorbidity.

The modified phosphoproteome profile of the homozygous mice in combination with human literature suggests a potential signaling pathway from constitutive TSHR signaling and cAMP activation, to the activation of ERK/MAPK signaling. This is the first time that a specific mechanism has been identified for a possible involvement of TSH signaling in thyroid carcinoma development.