Identification of deletions in children with congenital hypothyroidism and thyroid dysgenesis with the use of multiplex ligation-dependent probe amplification

Relationship between TSHR, BRAF and PIK3CA gene copy number variations and thyroid nodules

PURPOSE

This study aims to investigate the relationship between the TSHR, BRAF, and PIK3CA gene copy number variations (CNVs) and thyroid nodules by analyzing gene CNVs, and to explore the interaction between iodine status and the above genes CNVs in the occurrence of thyroid nodules.

METHODS

Three hundred and ninety-five subjects were selected from 3 regions with different iodine status in Shanxi Province of China, including 192 patients with thyroid nodules and 203 healthy controls. The basic information about subjects had been obtained through a questionnaire. B ultrasound was utilized to check thyroid nodules. Blood and urine samples were harvested to detect the thyroid function and urinary iodine concentration. Real-time quantitative polymerase chains reaction (RT-PCR) served to detect CNVs in DNA from human blood.

RESULTS

There was an association between TSHR gene CNV and thyroid nodules (χ² = 8.403, P = 0.004). The prevalence of BRAF and PIK3CA gene CNVs was not statistically significant between the case group and the control group. Differences in the TSHR gene CNV rates for cases of the 3 areas were statistically significant (χ² = 10.072, P = 0.007). No statistical difference in the prevalence rates of the 3 genes CNVs between diverse characteristics of thyroid nodules was observed. UIC > 300 μg/L (OR = 1.74, 95% CI: 1.02-2.96, P = 0.041) and TSHR gene CNV (OR = 3.53, 95% CI: 1.40-8.92, P = 0.008) were risk factors for thyroid nodules. There was no significant interaction between the UIC and the examined genes CNVs.

CONCLUSIONS

TSHR gene CNV and high urinary iodine levels can increase the risk of thyroid nodules. But the interactions between the 3 above genes CNVs and iodine nutrition were not found in the occurrence of thyroid nodules.

Further Evidence That Defects in Main Thyroid Dysgenesis-Related Genes Are an Uncommon Etiology for Primary Congenital Hypothyroidism in Mexican Patients: Report of Rare Variants in FOXE1, NKX2-5 and TSHR

Mexico shows a high birth prevalence of congenital hypothyroidism (CH) due to thyroid dysgenesis (TD). PAX8 defects underlie only 1% of these cases and NKX2-1 does not seem to be involved. Here, we analyzed other TD-related genes in 128 non-related Mexican patients (females 77.3%; 6 months to 16.6 years) with non-syndromic CH-TD diagnosis established by clinical evaluation, thyroid hormone serum profiling, and scintigraphy (74%) or ultrasonography (26%). We performed Sanger sequencing of FOXE1, NKX2-5, and TSHR and evaluated copy number variations (CNVs) in TSHR, FOXE1, PAX8, and NKX2-1 by multiplex ligation-dependent probe amplification. Odds ratios for TD risk were explored for FOXE1 polyalanine stretches [polyAla-rs71369530] in cases and controls (N = 116). Five rare missense changes cataloged as benign (NKX2-5:p.(Ala119Ser)-rs137852684), of unknown significance (FOXE1:p.(Ala335Gly)-rs543372757; TSHR:p.(Asp118Asn)-rs1414102266), and likely pathogenic (FOXE1:p.(Gly124Arg)-rs774035532; TSHR:p.(Trp422Arg)-rs746029360) accounted for 1.5% (N = 2/128) of clinically relevant genotypes (supported in part by protein modeling) in CH-TD. No CNVs were identified, nor did polyAla > 14 alanines in FOXE1 significantly protect against TD. The present and previously published data collectively show that small clinically relevant germline variants in PAX8, FOXE1, and TSHR are found in only a very small proportion (2.5%) of isolated CH-TD Mexican patients.

Congenital Hypothyroidism Patients With Thyroid Hormone Receptor Variants Are Not Rare: A Systematic Review

Background

Primary congenital hypothyroidism (CH) is a common endocrine and metabolic disease. Various genetic factors, including the thyroid hormone receptor (TSHR), play an important role in CH.

Aim

To explore the occurrence of pathogenic TSHR variants in CH.

Methods

We searched published articles in PubMed, Web of Science, and Cochrane Library databases, from the establishment of the database to September 26, 2021. Studies with sequencing partial or full exons of TSHR in CH patients were included. Gene polymorphism was excluded.

Results

A total of 66 articles (44 case-control studies and 22 case reports) were selected from the database. Though case-control studies, we found the incidence of pathogenic TSHR variants were not rare (range from 0% to 30.6%) and varied greatly in different countries and race. The pathogenic genotypes varied in different regions. All the variants were “loss-of-function” mutations, in which the p.(Arg450His) variant was the most common variant. In addition, we analyzed the case reports and found that CH patients with a family genetic background expressed homozygous genotypes. Homozygotes had more obvious symptoms of hypothyroidism and higher risk of comorbidities than heterozygotes.

Conclusion

Pathogenic TSHR variants are not uncommon cause of the CH, especially in the Arabs. The role of TSHR gene detection in the treatment of children with CH needs to be further studied.

Gene Variants in NKX2-1 Do Not Represent a Major Etiological Factor of Primary Congenital Hypothyroidism in Mexican Population

Congenital hypothyroidism (CH), attributable to thyroid dysgenesis (TD), has an unusually high prevalence in Mexican population but the causes are unknown. NKX2-1 , as a candidate gene, was subjected to automated Sanger sequencing in 122 unrelated Mexican patients with CH/TD. Although this study includes the largest number of TD-related CH patients in whom NKX2-1 has been analyzed, no pathogenic variants were detected; only three benign polymorphic changes were identified. These results suggest that NKX2-1 is not a major contributor to the etiology of CH or its high prevalence in Mexicans. Our work identifies misannotations of NKX2-1 variants in three previous published reports.

Resistance to thyrotropin

Resistance to thyrotropin (RTSH) is broadly defined as reduced sensitivity of thyroid follicle cells to stimulation by biologically active TSH due to genetic defects. Affected individuals have elevated serum TSH in the absence of goiter, with the severity ranging from nongoitrous isolated hyperthyrotropinemia to severe congenital hypothyroidism with thyroid hypoplasia. Conceptually, defects leading to RTSH impair both aspects of TSH-mediated action, namely thyroid hormone synthesis and gland growth. These include inactivating mutations in the genes encoding the TSH receptor and the PAX8 transcription factor. A common third cause has been genetically mapped to a locus on chromosome 15, but the underlying pathophysiology has not yet been elucidated. This review provides a succinct overview of currently defined causes of nonsyndromic RTSH, their differential diagnoses (autoimmune; partial iodine organification defects; syndromic forms of RTSH) and implications for the clinical approach to patients with RTSH.