Inherited Disorders of Thyroid Hormone Metabolism Defect Caused by the Dysregulation of Selenoprotein Expression

Serum klotho associated with thyroid hormone in adults: A population-based cross-sectional research

BACKGROUND AND STUDY AIM

The klotho protein, a multifunctional protein, has been shown to be associated with a wide range of endocrine diseases and has been linked to thyroid tumourigenesis. However, the relationship between serum klotho levels and thyroid hormones remains poorly understood. This study aimed to explore the correlation between serum klotho levels and thyroid hormones.

METHODS

Data was obtained from the NHANES cycles 2007-2008, 2009-2010, and 2011-2012. A total of 4674 participants were recruited for this study. Statistical analysis was using multiple linear regression analyses, and restricted cubic spline plots (RCS) to investigate the association between serum klotho levels and serum levels of thyroid hormones.

RESULTS

In the unadjusted covariate model, ln(klotho) significantly positively correlated with tT3, tT4, fT3, tT4/fT4, and tT3/fT3 (all P<0.01) and negatively correlated with TSH, tT4/tT3, and fT4/fT3 (all P<0.05). Furthermore, tT3, tT4, fT3and tT3/fT3 (P < 0.05) were still significant in the adjusted model. And it is worth noting that there is an approximately L-shaped nonlinear relationship between ln(klotho) and fT3,tT3 with a cut-off point of 6.697 (P-non-linear < 0.05). The stratification analysis showed gender and iodine level differences in the relationship between serum Klotho levels and thyroid hormones.

CONCLUSION

There is an L-shaped nonlinear relationship between ln(klotho) and fT3, tT3, suggesting that klotho could be involved in the physiological regulation of thyroid function.

Genetic Determinants of Selenium Availability, Selenium-Response, and Risk of Polycystic Ovary Syndrome

Selenium is a trace element and its deficiency has been associated with the risk of PCOS, a multifactorial syndrome that affects a large number of women worldwide. Several databases and literature were searched to find out genetic variants of the genes involved in selenium uptake, metabolism, and regulation which may be significantly associated with the risk of PCOS through Se-related pathways. Genes that require selenium for their biological actions to perform were also shortlisted. A total of eighteen significantly associated genes with forty-four variants were identified as candidate variants that could play a potential role in the modulation of PCOS risk among the study population. The genetic variant distribution data was available in-house and was obtained through a GWAS study of the North India population. In silico tools were applied to understand the functional impact of these variants. Three variants namely LDLR (rs2228671), TNF (rs1041981), and SAA2 (rs2468844) are strongly associated with PCOS risk and have a functional impact on encoded protein. Certain variants of Se uptake genes such as DIO1, GPX2, TXNRD1, DIO2 and GPX3 are also significantly associated with the risk of PCOS development. "C" allele of the Se transporter gene SELENOP (rs9686343) significantly increases PCOS risk. Other potential genes require selenium for their biological actions and are involved in the inflammatory, antioxidant response, and energy homeostasis signaling pathways. Thus, genetic variants of the population may affect the Se availability in the body. Also, deficiency of Se effects may get modulated due to underlying genetic polymorphism of Se-associated genes. This information may be helpful in dosage adjustment of Se supplementation for a population in order to get maximum benefits.

Effects of SARS-CoV-2 infection on hypothyroidism and subclinical hypothyroidism: a meta-analysis

Background

In recent years, the outbreak of COVID-19 caused by SARS-CoV-2 has been witnessed globally. However, the impact of SARS-CoV-2 infection on thyroid dysfunction and subclinical thyroid dysfunction remains unclear. Therefore, this meta-analysis aimed to assess the effects of SARS-CoV-2 infection on thyroid dysfunction and its relationship with the severity of COVID-19.

Methods

We systematically searched databases including PubMed, Willey Library, Embase, Web of Science, CNKI, Wanfang, and VIP. We focused on randomized controlled trials, case-control studies, and cohort studies published between December 2019 and August 2023, examining the association between SARS-CoV-2 infection and hypothyroidism, with a specific emphasis on the severity of the infection. The quality of the research was assessed using the Newcastle-Ottawa Scale (NOS), while statistical analysis was conducted using the meta and metafor packages in R 4.2.1 software.

Results

For the meta-analysis, a total of eight articles were identified based on strict inclusion and exclusion criteria. For the association between SARS-CoV-2 infection and hypothyroidism, three studies (266 samples) comparing TSH levels of COVID-19 and control groups showed no difference in TSH levels [SMD=-0.04,95%CI(-1.22,1.15),P=0.95]. Additionally, two studies examining TT3 (a sample of 176 cases) and two studies examining TT4 (a sample of 176 cases) also showed no difference in TT3 and TT4 between the COVID-19 group and the control group, respectively. However, when evaluating the severity of COVID-19, six studies (565 samples) showed that TSH in the severe group was significantly lower than in the mild group [SMD = -0.55, 95% CI (-0.96, -0.14)], while FT3 was also lower in the severe group [SMD = -0.96, 95% CI (-1.24, -0.67)]. No noticeable differences were observed between the severe and mild groups in their TT3, FT4, and TT4 levels.

Conclusion

SARS-CoV-2 infection may have detrimental effects on thyroid function in individuals with severe symptoms. More research is needed to confirm and explore this relationship.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42023486042.

Insights Obtained from the Nontumorous Glandular Tissue in Patients with Endocrine Tumors

The pathology of neoplasia tends to focus on the tumor that requires characterization, grading, and staging. However, nontumorous tissue surrounding the lesion can also provide information, particularly about pathogenetic mechanisms. In endocrine tissues, this takes the form of precursor lesions that characterize several genetic predisposition syndromes. In addition, because of the unique functional aspects of endocrine neoplasia, the nontumorous tissue provides evidence of hormone excess, with hyperplasia and/or atrophy and other involutional changes allowing the pathologist to confirm both hormone function by the tumor and the effects of medical therapies. In this article, we review the various clinically relevant features that should be assessed and reported to enhance clinical management of patients with endocrine neoplasms. For example, in thyroid there may be inflammatory thyroiditis or goiter of various etiologies; there may be C-cell hyperplasia either as a preneoplastic lesion in patients with genetic predisposition to medullary thyroid carcinoma or as a reactive phenomenon. Drug-induced changes can be seen in thyroid and adrenal cortex. In neuroendocrine tissues, the nontumorous tissues may show precursor lesions such as endocrine cell hyperplasia/dysplasia; there may be related or unrelated hyperplastic or neoplastic lesions. Some tissues, such as pituitary corticotrophs and adrenal cortex, develop changes that reflect feedback suppression by hormone excess that can serve as biomarkers of tumor functionality and provide enhanced clinicopathologic correlates.

Selenium, Iodine and Iron-Essential Trace Elements for Thyroid Hormone Synthesis and Metabolism

The adequate availability and metabolism of three essential trace elements, iodine, selenium and iron, provide the basic requirements for the function and action of the thyroid hormone system in humans, vertebrate animals and their evolutionary precursors. Selenocysteine-containing proteins convey both cellular protection along with H₂O₂-dependent biosynthesis and the deiodinase-mediated (in-)activation of thyroid hormones, which is critical for their receptor-mediated mechanism of cellular action. Disbalances between the thyroidal content of these elements challenge the negative feedback regulation of the hypothalamus-pituitary-thyroid periphery axis, causing or facilitating common diseases related to disturbed thyroid hormone status such as autoimmune thyroid disease and metabolic disorders. Iodide is accumulated by the sodium-iodide-symporter NIS, and oxidized and incorporated into thyroglobulin by the hemoprotein thyroperoxidase, which requires local H₂O₂ as cofactor. The latter is generated by the dual oxidase system organized as 'thyroxisome' at the surface of the apical membrane facing the colloidal lumen of the thyroid follicles. Various selenoproteins expressed in thyrocytes defend the follicular structure and function against life-long exposure to H₂O₂ and reactive oxygen species derived therefrom. The pituitary hormone thyrotropin (TSH) stimulates all processes required for thyroid hormone synthesis and secretion and regulates thyrocyte growth, differentiation and function. Worldwide deficiencies of nutritional iodine, selenium and iron supply and the resulting endemic diseases are preventable with educational, societal and political measures.