Impact of phosphodiesterase 8B gene rs4704397 variation on thyroid homeostasis in childhood obesity

Association between non-alcoholic fatty liver disease and subclinical hypothyroidism in children with obesity

PURPOSE

We aimed (i) evaluating the relationship between non-alcoholic fatty liver disease (NAFLD) and thyroid function tests, (ii) testing if the relationship between NAFLD and thyroid dysfunction could be driven by the obesity and the IR degree, and (iii) exploring the influence of the patatin-like phospholipase domain-containing protein-3 (PNPLA3) I148M and the transmembrane 6 superfamily member 2 (TM6SF2) E167K polymorphisms on the association between NAFLD and thyroid function in children.

METHODS

We examined 2275 children and adolescents with obesity. Subclinical hypothyroidism (SH) was defined by thyroid-stimulating hormone (TSH) > 4.2 μUI/ml with normal fT3 and fT4.

RESULTS

Children with NAFLD showed higher SH prevalence than those without NAFLD (15.7% Vs 7.4%;p = 0.001) and showed an adjusted odds ratio (aOR) to have SH of 1.68 (95% CI:1.01-2.80;p = 0.04) while patients with SH had an aOR to show NAFLD of 2.13(95% CI:1.22-3.73;p = 0.008). Patients having severe obesity and IR degree presented an aOR to show both NAFLD and SH of 3.61 (95% CI:1.78-7.33;p < 0.0001). Subjects with NAFLD carrying the TM6SF2 167 K allele had lower TSH levels than non-carriers (p = 0.03) and showed an aOR to have SH of 0.10 (95% CI: 0.01-0.79;p = 0.02). No differences were found in carriers of the PNPLA3 148 M allele. A general linear model for TSH variance showed a significant association of TSH with TM6SF2 genotypes only in the NAFLD group (p = 0.001).

CONCLUSION

Children with obesity and NAFLD presented increase risk of SH and vice versa likely due to the adverse effect of duration of obesity, obesity degree, and IR. The TM6SF2 E167K exerts a protective role against SH in children with obesity and NAFLD.

A genome-wide association study of thyroid stimulating hormone and free thyroxine in Danish children and adolescents

Background

Hypothyroidism is associated with obesity, and thyroid hormones are involved in the regulation of body composition, including fat mass. Genome-wide association studies (GWAS) in adults have identified 19 and 6 loci associated with plasma concentrations of thyroid stimulating hormone (TSH) and free thyroxine (fT4), respectively.

Objective

This study aimed to identify and characterize genetic variants associated with circulating TSH and fT4 in Danish children and adolescents and to examine whether these variants associate with obesity.

Methods

Genome-wide association analyses of imputed genotype data with fasting plasma concentrations of TSH and fT4 from a population-based sample of Danish children, adolescents, and young adults, and a group of children, adolescents, and young adults with overweight and obesity were performed (N = 1,764, mean age = 12.0 years [range 2.5−24.7]). Replication was performed in additional comparable samples (N = 2,097, mean age = 11.8 years [1.2−22.8]). Meta-analyses, using linear additive fixed-effect models, were performed on the results of the discovery and replication analyses.

Results

No novel loci associated with TSH or fT4 were identified. Four loci previously associated with TSH in adults were confirmed in this study population (PDE10A (rs2983511: β = 0.112SD, p = 4.8 ∙ 10⁻¹⁶), FOXE1 (rs7847663: β = 0.223SD, p = 1.5 ∙ 10⁻²⁰), NR3C2 (rs9968300: β = 0.194SD), p = 2.4 ∙ 10⁻¹¹), VEGFA (rs2396083: β = 0.088SD, p = 2.2 ∙ 10⁻¹⁰)). Effect sizes of variants known to associate with TSH or fT4 in adults showed a similar direction of effect in our cohort of children and adolescents, 11 of which were associated with TSH or fT4 in our study (p<0.0002). None of the TSH or fT4 associated SNPs were associated with obesity in our cohort, indicating no pleiotropic effects of these variants on obesity.

Conclusion

In a group of Danish children and adolescents, four loci previously associated with plasma TSH concentrations in adults, were associated with plasma TSH concentrations in children, suggesting comparable genetic determinants of thyroid function in adults and children.

Subclinical hypothyroidism in children

NEED AND PURPOSE OF REVIEW

Subclinical hypothyroidism is a biochemical diagnosis characterized by raised thyroid stimulating hormone and normal free T4, without clinical features of hypothyroidism. This review analyzes the current evidence to arrive at a consensus and algorithm to manage this condition.

METHODS

We searched Pubmed, Cochrane and Embase for articles published between 1990 to 2014, and identified 13 relevant articles dealing with pediatric subclinical hypothyroidism which were suitable to include in our review.

CONCLUSIONS

Subclinical hypothyroidism is often a benign problem which requires expectant management with periodic monitoring of thyroid function tests and natural progression to overt hypothyroidism occur lot less frequently than expected. There is a paucity of robust randomized intervention studies, especially studies focusing on clinical outcomes. Thyroid replacement therapy is not justified in children with subclinical hypothyroidism when Thyroid stimulating hormone is <10 mIU/L. The main risk factors for progression to overt hypothyroidism are female sex, goiter, family history of thyroid disorder, strongly positive thyroid peroxidase antibodies and symptoms suggesting hypothyroidism. An algorithm for managing this condition is suggested.

The phosphodiesterase 8B gene rs4704397 is associated with thyroid function, risk of myocardial infarction, and body height: the Tromsø study

OBJECTIVE

High serum thyrotropin (TSH) levels predict cardiovascular disease (CVD). Recently several single nucleotide polymorphisms (SNPs) associated with TSH levels have been identified, one of them being the rs4704397 SNP in the phosphodiesterase 8B (PDE8B) gene. If the relation between thyroid function and CVD is causal, one could also expect rs4704397 genotypes to predict CVD and possibly health in general.

METHODS

DNA was prepared and genotyping performed for rs4704397 in subjects who participated in the fourth survey of the Tromsø Study in 1994-1995 and who were registered with the endpoints myocardial infarction (MI), type 2 diabetes (T2DM), cancer, or death, as well as a randomly selected control group. Similarly, genotyping was performed in subjects who had participated in clinical trials where serum TSH, free T4 (fT4), and free T3 (fT3) were measured.

RESULTS

From the Tromsø Study, 8938 subjects without thyroid disease or thyroid medication were successfully genotyped for rs4704397. Among these, 2098 were registered with MI, 1025 with T2DM, 2748 with cancer, and 3592 had died. The minor homozygote genotype (A:A) had a median serum TSH level that was 0.29 mIU/L higher than in the major homozygote genotype (G:G). The A:A genotype had a significantly increased risk of MI as compared to the G:G genotype (1.14 [1.00-1.29], hazard ratio [confidence interval], Cox regression with adjustment for age, sex, and body mass index). No significant associations were seen with the other endpoints or CVD risk factors. Furthermore, subjects with the G:G genotype were significantly taller than subjects with the A:A genotype (mean difference 1.5 cm). In 584 subjects with serum TSH, fT4, and fT3 measurements, the subjects with the A:A genotype had significantly higher serum TSH and nonsignificantly lower serum fT3 (mean difference 0.15 pmol/L) levels than subjects with the G:G genotype.

CONCLUSION

rs4704397 is associated with thyroid function, risk of MI, and body height. However, confirmation in other cohorts is needed before firm conclusions can be drawn.

Frequency and effect on serum TSH of phosphodiesterase 8B (PDE8B) gene polymorphisms in patients with sporadic nonautoimmune subclinical hypothyroidism

BACKGROUND

Nonautoimmune subclinical hypothyroidism (NSH) is characterized by elevated serum TSH in presence of normal thyroid hormone levels and absence of anti-thyroid antibodies. As result of a genomic-wide study, a strong association between three polymorphic variants in intron 1 of human PDE8B gene (rs4704397, rs6885099, rs2046045) and serum TSH has been reported in euthyroid subjects.

AIM

The aim of this study was to evaluate frequency and effects on serum TSH of PDE8B gene polymorphisms in patients with sporadic NSH and verify if differences in serum TSH levels are associated to these polymorphic variants.

SUBJECTS AND METHODS

A total of 58 Italian selected patients affected by NSH, with elevated serum TSH, normal FT3 and FT4 and without TSHr gene mutations, were subjected to genotyping for specific single nucleotide polymorphism of PDE8B gene.

RESULTS

In all patients, the integrity of TSH receptor gene was attested. The ancestral allele associated with increased serum TSH was present in 42/58 patients (72.4 %) for rs4704397, in 42/58 patients (72.4 %) for rs6885099 and in 44/58 patients (75.9 %) for rs2046045. However, similar values of serum TSH were detected in patients with minor or major allele for each polymorphism.

CONCLUSIONS

A prevalence of the minor allele of PDE8B gene polymorphism associated with elevated serum levels of TSH was demonstrated in patients affected by sporadic NSH; however, significant differences in circulating TSH in patients with minor or major alleles for each polymorphism were not identified demonstrating the lack of association between the polymorphisms and serum TSH levels in these patients.

Genetic associations with neonatal thyroid-stimulating hormone levels

BACKGROUND

Elevations or deficits in thyroid hormone levels are responsible for a wide range of neonatal and adult phenotypes. Several genome-wide, candidate gene, and meta-analysis studies have examined thyroid hormones in adults; however, to our knowledge, no genetic association studies have been performed with neonatal thyroid levels.

METHODS

A population of Iowa neonates, term (n = 827) and preterm (n = 815), were genotyped for 45 single-nucleotide polymorphisms (SNPs). Thyroid-stimulating hormone (TSH) values were obtained from the Iowa Neonatal Metabolic Screening Program. ANOVA was performed to identify genetic associations with TSH concentrations.

RESULTS

The strongest association was rs4704397 in the PDE8B gene (P = 1.3 × 10(-4)), followed by rs965513 (P = 6.4 × 10(-4)) on chromosome 9 upstream of the FOXE1 gene. Both of these SNPs met statistical significance after correction for multiple testing. Six other SNPs were marginally significant (P < 0.05).

CONCLUSION

We demonstrated for the first time two genetic associations with neonatal TSH levels that replicate findings with adult TSH levels. These SNPs should be considered early predictors of risk for adult diseases and conditions associated with thyroid hormone levels. Furthermore, this study provides a better understanding of the thyroid profile and potential risk for thyroid disorders in newborns.

Endocrine disorders in childhood and adolescence. Natural history of subclinical hypothyroidism in children and adolescents and potential effects of replacement therapy: a review

OBJECTIVE

Subclinical hypothyroidism (SH) is quite common in children and adolescents. The natural history of this condition and the potential effects of replacement therapy need to be known to properly manage SH. The aim of this review is to analyze: i) the spontaneous evolution of SH, in terms of the rate of reversion to euthyroidism, the persistence of SH, or the progression to over hypothyroidism; and ii) the effects of replacement therapy, with respect to auxological data, thyroid volume, and neuropsychological functions.

METHODS

We systematically searched PubMed, Cochrane, and EMBASE (1990-2012) and identified 39 potentially relevant articles of which only 15 articles were suitable to be included.

RESULTS AND CONCLUSIONS

SH in children is a remitting process with a low risk of evolution toward overt hypothyroidism. Most of the subjects reverted to euthyroidism or remained SH, with a rate of evolution toward overt hypothyroidism ranging between 0 and 28.8%, being 50% in only one study (nine articles). The initial presence of goiter and elevated thyroglobulin antibodies, the presence of celiac disease, and a progressive increase in thyroperoxidase antibodies and TSH value predict a progression toward overt hypothyroidism. Replacement therapy is not justified in children with SH but with TSH 5-10 mIU/l, no goiter, and negative antithyroid antibodies. An increased growth velocity was observed in children treated with levothyroxine (l-T(4); two articles). l-T(4) reduced thyroid volume in 25-100% of children with SH and autoimmune thyroiditis (two studies). No effects on neuropsychological functions (one study) and posttreatment evolution of SH (one study) were reported.

Subclinical hypothyroidism in children

The prevalence of SH in the pediatric population is < 2%, the caveat being the limited number of studies addressing SCH in the pediatric population. congenital deveolopental anamolies. Mutations in the several proteins are important causes of this condition. Despite the limited data available, SCH in children and adolescents appears to be a benign and remitting disease with a low risk of evolution to OH. It appears that thyroid hormones appear to be functioning well despite elevated TSH. Predictors of progression include, goiter, celiac disease, and positive anti TPO.