Thyroid hormones are critical for early neurocognitive development as well as growth and development throughout childhood. Prompt recognition and treatment of hypothyroidism is, therefore, of utmost importance to optimize physical and neurodevelopmental outcomes. A PubMed search was completed in Clinical Queries using the key terms “hypothyroidism”. Hypothyroidism may be present at birth (congenital hypothyroidism) or develop later in life (acquired hypothyroidism). Thyroid dysgenesis and dyshormonogenesis account for approximately 85% and 15% of permanent cases of congenital primary hypothyroidism, respectively. More than 95% of infants with congenital hypothyroidism have few, if any, clinical manifestations of hypothyroidism. Newborn screening programs allow early detection of congenital hypothyroidism. In developed countries, Hashimoto thyroiditis is the most common cause of goiter and acquired hypothyroidism in children and adolescents. Globally, iodine deficiency associated with goiter is the most common cause of hypothyroidism. Central hypothyroidism is uncommon and may be associated with other congenital syndromes and deficiencies of other pituitary hormones. Familiarity of the clinical features would allow prompt diagnosis and institution of treatment. To optimize neurocognitive outcome in infants with congenital hypothyroidism, treatment with levothyroxine should be started as soon as possible, preferably within the first 2 weeks of life. Children with acquired hypothyroidism should also be treated early to ensure normal growth and development as well as cognitive outcome. The target is to keep serum TSH < 5 mIU/L and to maintain serum free T4 or total T4 within the upper half of the age-specific reference range, with elimination of all symptoms and signs of hypothyroidism.

Evaluation and management of the child with hypothyroidism

Context: The DUOX/DUOXA systems play a key role in H2O2 generation in thyroid cells, which is required for iodine organification and thyroid hormone synthesis. DUOX2/DUOXA2 defects can cause congenital hypothyroidism (CH), but it is unknown whether DUOX1/DUOXA1 mutations can also cause CH. Objective: We aimed to identify DUOX1/DUOXA1 mutations and explore their role in the development of CH by investigating their functional impacts on H2O2 generation. Patients and Methods: Forty-three children with CH with goiter were enrolled, in whom all exons and flanking intronic regions of DUOX1/DUOXA1 were directly sequenced. We characterized the functional effects of identified mutations on the expression of DUOX1 and DUOXA1 and H2O2 generation. Results: We identified a heterozygous DUOX1 missense mutation (G > A base substitution at nucleotide 3920 in exon 31) that changed a highly conserved arginine to glutamine at residual 1307 (p.R1307Q) in patient 1. A heterozygous-missense mutation (c.166 C>T; p.R56W) was identified in DUOXA1 in patient 2. Functional studies demonstrated that both p.R1307Q mutant or p.R56W mutant decreased the DUOX1 expression at mRNA and protein levels, with a corresponding impairment in H2O2 generation (P < 0.01). The results also showed that intact DUOXA1 was required for full activity of DUOX1 and H2O2 generation. Conclusions: We have identified two heterozygous missense mutations in DUOX1 and DUOXA1 in two patients that can cause CH through disrupting the coordination of DUOX1 and DUOXA1 in the generation of H2O2. This study for the first time demonstrates that the DUOX1/DUOXA1 system, if genetically defective, can cause CH.

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Identification of Two Missense Mutations in DUOX1 (p.R1307Q) and DUOXA1 (p.R56W) That Can Cause Congenital Hypothyroidism Through Impairing H2O2 Generation

Levothyroxine treatment is associated with an increased relative risk of overall and organ specific incident cancers - a cohort study of the Swedish population.

The possible adverse or positive effects of levothyroxine treatment among patients with atrial fibrillation have been debated. Atrial fibrillation, levothyroxine treatment, and dementia are common among older adults, yet little is known about the effects of levothyroxine on the development of dementia. The study population included all adults (n = 12,057) aged ≥ 45 years with a diagnosis of atrial fibrillation at 75 primary care centers in Sweden during 2001–2007 without an earlier recorded dementia diagnosis. Patients with a diagnosis of hypothyroidism and levothyroxine prescription (n = 756; 180 men and 576 women), or with a prescription without this diagnosis (n = 415, 100 men and 315 women), were compared to patients without a diagnosis and prescription (n = 10,886). Cox regression was performed, with hazard ratios and 95% confidence intervals, with outcome defined as dementia of all causes until 31 December, 2010. During a mean 5.7 years (standard deviation 2.4 years) of follow-up, a total of 749 patients with atrial fibrillation (6.2%) were diagnosed with dementia. Women with hypothyroidism and a levothyroxine prescription showed lower hazard ratios (0.61; 0.41–0.90) in adjusted Cox regression models (age, socioeconomic factors, co-morbidity, and warfarin treatment). Levothyroxine prescription without hypothyroidism was non-significant. We found that women with atrial fibrillation with levothyroxine treatment and hypothyroidism have a lower risk of incident dementia than women with atrial fibrillation without levothyroxine treatment and no hypothyroidism. The results should be confirmed in larger studies.

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Effect of Levothyroxine Treatment on Incident Dementia in Adults with Atrial Fibrillation and Hypothyroidism.

The incidence of congenital hypothyroidism (CH) in newborn infants ranges from 1 in 3,000 to 1 in 4,000. Previous studies have indicated the neuroprotective role of microRNA (miR)-124-3p, however the expression and role of miR-124-3p in CH remain unclear. Therefore, the present study was performed to investigate the role and precise molecular mechanism of miR-124-3p in CH. Propylthiouracil (50 mg/day) was injected into the stomach of pregnant rats from gestational day 15 until parturition in order to establish a thyroid hypofunction model. Newborn rats were divided into the following four groups: The control group; the thyroid hypofunction group; the miR-124-3p mimic group; and the miR-124-3p negative control group. Reverse transcription-quantitative polymerase chain reaction indicated that miR-124-3p was significantly decreased in the hippocampus of the thyroid hypofunction group compared with the control group. Bioinformatics software was used to predict mRNA targets recognized by miR-124-3p and the programmed cell death protein 6 (PDCD6) 3' untranslated region (UTR) was demonstrated to exhibit the seed sequence of miR-124-3p. The interaction between miRNA-124-3p and PDCD6 was then verified using a dual-luciferase reporter assay system. PDCD6 expression was significantly increased in the hippocampus of rats with CH compared with the control group. Flow cytometry was performed to investigate the effects of miR-124-3p on neuronal cell apoptosis and the results indicated that the apoptosis rate in the thyroid hypofunction group was significantly increased compared with the control group; this increase was reversed by transfection with miR-124-3p mimics. Western blot analysis was used to detect the levels of cleaved poly [ADP-ribose] polymerase (PARP), full-length PARP, caspase-3, B cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax) proteins. The results indicated that the expression of cleaved PARP, caspase-3 and Bax protein were significantly increased and the expression of full-length PARP and Bcl-2 protein was significantly decreased compared with the control group. These effects were reversed by miRNA-124-3p mimic transfection. Taken together, the results of the present study demonstrate that miRNA-124-3p serves a protective role in CH via targeting PDCD6.

/pdf/microrna-124-3p-inhibits-the-progression-of-congenital-1tuv1i8203.pdf

microRNA‑124‑3p inhibits the progression of congenital hypothyroidism via targeting programmed cell death protein 6

Background: Thyroid hormone (T3) is essential for normal development of children enabling braindevelopment and somatic growth. However, certain individuals are genetically predisposed with insufficient or nothyroid hormones. Such a condition is termed congenital hypothyroidism (CH).Objective: In the present review, a brief back ground about congenital hypothyroidism, factors associated withCH leading to thyroid dysgenesis and thyroid dyshormonogenesis is elaborated. Additionally, the guidelines foravailable treatment options, management and follow-up required for patients diagnosed with CH are discussed.Treatment options in terms of treatment initiation and dosage of hormone replacement are discussed.Conclusion: Though CH is considered as the most common neonatal metabolic disorder, it is also easily treatablecompared to other metabolic or hereditary diseases. The outcome of CH treatment depends on the compliance ofparents early in life and by patients themselves during later part of life.

Congenital Hypothyroidism: Facts, Facets & Therapy.

The objective of the current study is to explore the association of thyroid-stimulating hormone receptor (TSHR) rs1991517 polymorphism (c.2337 C > G, p.D727E) with congenital hypothyroidism (CH) through a case–control study followed by a meta-analysis. The case–control study was based on 45 CH subjects and 700 healthy controls. Meta-analysis comprised of seven published studies and our current findings (1044 CH cases and 1649 healthy controls). The allele contrast model showed that the presence of G- allele increased CH risk by 45% (OR: 1.45, 95% CI 1.20–1.76) and 41% (OR: 1.41, 95% CI 1.03–1.93) in fixed effect and random effect models, respectively. The GG- genotype is associated with 2.3-fold (95% CI 1.32–3.99) increased risk for CH in the fixed-effect model. I2 (0.58) and Cochran’s Q test (Q: 16.72, p = 0.02) revealed evidence of heterogeneity in the association. No publication bias was observed by Egger’s test (p = 0.70). Sensitivity analysis revealed that even after excluding any study this polymorphism is associated with risk for CH. The rs1991517 mutation alters the binding affinity to cAMP (ΔG of 727D vs.727E: − 7.27 vs. − 7.34 kcal/mol). In conclusion, rs1991517 is a genetic risk factor for CH and exerts its impact by altering cAMP-mediated signal transduction.

The rs1991517 polymorphism is a genetic risk factor for congenital hypothyroidism

High prevalence of congenital hypothyroidism (CH) among Indian newborns prompted us to establish population-specific reference ranges of TSH and to explore the contribution of the common genetic variants in TSHR, TPO, TG and DUOX2 genes towards CH. A total of 1144 newborns (593 males and 551 females) were screened for CH. SNV profiling (n = 22) spanning three candidate genes, i.e. TSHR, TPO and TG was carried out in confirmed CH cases (n = 45). In screen negative cases (n = 700), ten TSHR variants were explored to establish association with CH. No mutation found in DUOX2. The 2.5th to 97.5th percentiles of TSH in these newborns were 0.5 to 12.2 mU/L. In newborns with optimal birth weight, the cut-off was 10 mU/L. Lower or higher birth weight resulted in slightly higher TSH. Two TSHR variants, i.e. rs7144481 and rs17630128 were associated with agenesis, hypoplasia and goiter. The rs2268477 was associated with agenesis and hypoplasia. The rs1991517, rs2075176 and rs2241119 were associated with agenesis only. The rs7144481, rs17630128, rs1991517 and rs2268477 were associated with 2.17, 4.62, 2.91 and 2.29-fold increased risk for CH, respectively. Among the TPO variants, rs867983 and rs2175977 were associated with agenesis and goiter, respectively. Among the TG variants, rs2076740 showed association with agenesis and goiter. Two rare variants i.e. TPO g.IVS14-19 G>C and TG c.1262 C>T were observed in CH cases. No genetic variant identified in the two exons of DUOX2. To conclude, the current study established Indian population-specific normative values for TSH and demonstrates specific genotype–phenotype correlations among three candidate genes.

Newborn screening and single nucleotide variation profiling of TSHR, TPO, TG and DUOX2 candidate genes for congenital hypothyroidism.

Valsartan in combination with metformin and gliclazide in diabetic rat model using developed RP-HPLC method

In our previous studies, we have demonstrated the association of certain variants of the thyroid-stimulating hormone receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (TG) genes with congenital hypothyroidism. Herein, we explored the mechanistic basis for this association using different in silico tools. The mRNA 3'-untranslated region (3'-UTR) plays key roles in gene expression at the post-transcriptional level. In TSHR variants (rs2268477, rs7144481, and rs17630128), the binding affinity of microRNAs (miRs) (hsa-miR-154-5p, hsa-miR-376a-2-5p, hsa-miR-3935, hsa-miR-4280, and hsa-miR-6858-3p) to the 3'-UTR is disrupted, affecting post-transcriptional gene regulation. TPO and TG are the two key proteins necessary for the biosynthesis of thyroid hormones in the presence of iodide and H2O2. Reduced stability of these proteins leads to aberrant biosynthesis of thyroid hormones. Compared to the wild-type TPO protein, the p.S398T variant was found to exhibit less stability and significant rearrangements of intra-atomic bonds affecting the stoichiometry and substrate binding (binding energies, ΔG of wild-type vs. mutant: ‒15 vs. ‒13.8 kcal/mol; and dissociation constant, Kd of wild-type vs. mutant: 7.2E-12 vs. 7.0E-11 M). The missense mutations p.G653D and p.R1999W on the TG protein showed altered ΔG (0.24 kcal/mol and 0.79 kcal/mol, respectively). In conclusion, an in silico analysis of TSHR genetic variants in the 3'-UTR showed that they alter the binding affinities of different miRs. The TPO protein structure and mutant protein complex (p.S398T) are less stable, with potentially deleterious effects. A structural and energy analysis showed that TG mutations (p.G653D and p.R1999W) reduce the stability of the TG protein and affect its structure-functional relationship.

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Yedukondalu Kollati

Papers

Congenital Hypothyroidism: Facts, Facets & Therapy.

The rs1991517 polymorphism is a genetic risk factor for congenital hypothyroidism

Newborn screening and single nucleotide variation profiling of TSHR, TPO, TG and DUOX2 candidate genes for congenital hypothyroidism.

Valsartan in combination with metformin and gliclazide in diabetic rat model using developed RP-HPLC method

Molecular insights into the role of genetic determinants of congenital hypothyroidism