Mild subclinical hypothyroidism is associated with paediatric dyslipidaemia

Efficacy of Thyroid Hormone Replacement Therapy in Nasopharyngeal Carcinoma Patients with Radiation-Induced Subclinical Hypothyroidism

AIMS

Hypothyroidism is a common side effect of radiotherapy for nasopharyngeal carcinoma. However, the impact of thyroid hormone replacement therapy on patients with radiation-induced subclinical hypothyroidism has not been extensively explored. This study aimed to analyze the efficacy of thyroid hormone replacement therapy in nasopharyngeal carcinoma patients with subclinical hypothyroidism.

METHODS

Patients diagnosed with nasopharyngeal carcinoma who developed subclinical hypothyroidism after definitive radiotherapy between September 2019 and December 2020 were selected for inclusion in this study. Prior to thyroid hormone replacement therapy and after maintaining euthyroidism for 6-12 months through thyroid hormone replacement therapy, assessments using the SF36 Brief Health Status Scale and the Hypothyroidism-related Symptom Questionnaire were conducted via trained questionnaires. Lipid profiles were assessed at baseline and after 6-12 months of thyroid hormone replacement therapy. Statistical analyses were performed using matched samples T-test or Mann-Whitney U test.

RESULTS

The median follow-up period was 14.5 months. The median score of hypothyroid symptoms was 5.5 out of 19 points, with the most common symptoms being chills (65.0%), fatigue (50.0%), weight gain (45.0%), and limb numbness (40.0%). Thyroid hormone replacement therapy did not significantly improve the quality of life, hypothyroidism-related symptoms, or blood lipid profile in patients. However, there was an observed downward trend in serum cholesterol levels following treatment (P=0.052).

CONCLUSION

Thyroid hormone replacement therapy did not have a significant impact on alleviating hypothyroid symptoms, improving quality of life, or enhancing lipid profiles in patients with radiation-induced subclinical hypothyroidism. Nevertheless, a potential decrease in serum cholesterol levels was noted after thyroid hormone replacement therapy.

Update on dyslipidemia in hypothyroidism: the mechanism of dyslipidemia in hypothyroidism

Hypothyroidism is often associated with elevated serum levels of total cholesterol, LDL-C and triglycerides. Thyroid hormone (TH) affects the production, clearance and transformation of cholesterol, but current research shows that thyroid-stimulating hormone (TSH) also participates in lipid metabolism independently of TH. Therefore, the mechanism of hypothyroidism-related dyslipidemia is associated with the decrease of TH and the increase of TSH levels. Some newly identified regulatory factors, such as proprotein convertase subtilisin/kexin type 9, angiogenin-like proteins and fibroblast growth factors are the underlying causes of dyslipidemia in hypothyroidism. HDL serum concentration changes were not consistent, and its function was reportedly impaired. The current review focuses on the updated understanding of the mechanism of hypothyroidism-related dyslipidemia.

No association between subclinical hypothyroidism and dyslipidemia in children and adolescents

Background

There are controversies about the correlation between higher levels of thyroid stimulating hormone (TSH) and dyslipidemia in children. This study was designed to assess the relation between lipid profile components and TSH levels in children.

Method

This cross-sectional study was performed in a pediatric endocrinology growth assessment clinic in Shiraz, southern Iran. Children aged 2–18 years who referred to the clinic from January until April 2018 were included. TSH levels equal or above 5 mIU/L and lower than 10 mIU/L with normal free T4 (FT4) were considered as having subclinical hypothyroidism (SH).

Results

Six hundred sixty-six children were euthyroid while 181 had SH. No significant difference was found between the mean serum total cholesterol (P = 0.713), LDL-C (P = 0.369), HDL-C (P = 0.211), non-HDL-C (P = 0.929), and triglyceride (P = 0.215) levels between euthyroid children and subjects with SH. There was also no significant difference in the prevalence of dyslipidemias in any lipid profile components between the two groups. The adjusted correlation was not significant between TSH levels and any lipid profile component.

Conclusion

Based on the results of our study, we found no correlation between SH and dyslipidemia in children. The association between dyslipidemia and SH in children still seems to be inconsistent based on the results of this and previous studies. We recommend a meta-analysis or a significantly larger retrospective study on this subject.

The effect of subclinical hypothyroidism on body composition parameters in children

BACKGROUND

It's known that overt hypothyroidism increases body fat content and weight. There's limited research about the effect of subclinical hypothyroidism (SH) on body composition in children and the effect of LT4 treatment. We aimed to evaluate body composition parameters in healthy subjects and in children with mild SH (MSH) and determine the effect of LT4 treatment.

METHODS

Sixty-four healthy children and 32 children with MSH were included. Anthropometric measurements and hormonal parameters were evaluated. Body composition was evaluated using bioelectric impedance analysis (BIA). Patients were put on LT4 treatment. BIA was performed again after 12 months of therapy.

RESULTS

There was no significant difference between the anthropometric parameters and basal metabolic rate of the healthy children and the MSH group. The percentage of trunk muscle mass (TMM) in the MSH group was lower than in the control group (P < .05). After 12 months of LT4 treatment, the percentage of total fat-free mass (FFM), TMM and trunk fat-free mass (TFFM) were increased and percentage of total body fat mass and trunk fat mass were decreased (P < .05). The difference between the percentage of TMM in the MSH group and control group was insignificant after LT4 treatment (P > .05).

CONCLUSIONS

The percentage of TMM in children with MSH was found lower than healthy control group. After LT4 treatment, the percentage of the FFM, TMM and TFFM were increased and the difference between percentage of TMM in children with MSH and healthy controls was insignificant. Our data indicated that MSH might be associated with early changes in body composition parameters.

Less Favorable Lipid Profile and Higher Prevalence of Thyroid Antibodies in Women of Reproductive Age with High-Normal TSH-Retrospective Study

High-normal TSH can be associated with metabolic abnormalities and infertility. Aims of this study are to analyze retrospectively if routinely measured blood laboratory and anthropometric parameters differ between women of reproductive age with TSH < 2.5 mIU/L and with TSH ≥ 2.5 mIU/L. Retrospective analysis was performed in 466 female inpatients, aged 13–51, hospitalized in an endocrine department. The group of 280 patients with normal thyroid tests (TSH 0.27-4.2 mIU/L; normal FT3 and FT4) was selected and it was divided into two subgroups, i.e., with TSH < 2.5 mIU/L and TSH ≥ 2.5 mIU/L (n = 66; 23.6%). After excluding patients on L-thyroxine treatment (n = 240), those with TSH ≥ 2.5 mIU/L constituted 22.92% (n = 55). In the group of 280 patients with normal thyroid tests, an abnormally high concentration of triglycerides and an abnormally low HDLC/cholesterol ratio occurred more frequently in women with TSH ≥ 2.5 mIU/L than those with TSH < 2.5 mIU/L (17% vs. 7%, p = 0.017; 14% vs. 5%, p = 0.015, respectively). Increased concentration of thyroid antibodies, i.e., TPOAb, occurred more frequently in patients with TSH ≥ 2.5 mIU/L than those with TSH < 2.5 mIU/L (27% vs. 9%, p = 0.001). The same differences were found in the group of 240 patients after excluding those on L-thyroxine treatment. Blood lymphocyte concentration was the only independent linear parameter associated with TSH ≥ 2.5 mIU/L (OR = 1.551, p = 0.024) but only in the group of 280 patients with normal thyroid tests. TSH concentration correlated positively with blood lymphocyte (r = 0.129, p = 0.031) and TPOAb (r = 0.177, p = 0.005) concentrations but only in the group of 280 patients with normal thyroid tests. Less favorable lipid profiles and a higher prevalence of thyroid antibodies in women of reproductive age with high-normal TSH suggests that L-thyroxine treatment should be considered in such patients. The significance of a positive association between high-normal TSH and blood lymphocytes requires further evaluation.

Patterns of amiodarone-induced thyroid dysfunction in infants and children

BACKGROUND

Heart Rhythm Society guidelines recommend obtaining thyroid function tests (TFTs) at amiodarone initiation and every 6 months thereafter in adults, with no specific pediatric recommendations. Untreated hypothyroidism in young children negatively affects brain development and somatic growth, yet the optimal screening frequency for pediatric patients remains unclear, and limited data exist on pediatric amiodarone-induced thyroid dysfunction.

OBJECTIVE

The purpose of this study was to describe the patterns of amiodarone-induced thyroid dysfunction in pediatric patients.

METHODS

We established a retrospective cohort of 527 pediatric patients who received amiodarone between 1997 and 2017. We defined amiodarone therapy lasting 3-30 days as "short term" and >30 days as "long term."

RESULTS

The final cohort (n = 150) consisted of 27 neonates (18%), 25 infants (16%), 27 young children (18%), and 71 children (47%). Of the children in whom TFTs were checked, half (50.8%) developed a thyroid-stimulating hormone (TSH) value above the reference for age. Neonates had the highest median peak TSH values in both short- and long-term groups: 23.5 mIU/L (interquartile range 11.4-63.1) and 28.8 mIU/L (interquartile range 11.4-34.4), respectively. Although concurrent use of inotropic support was significantly associated with lower initial TSH values, no variable related to cardiac illness or type of heart disease was associated with peak TSH values.

CONCLUSION

Neonates and infants receiving amiodarone had more thyroid dysfunction with greater degrees of TSH elevation than older children. TSH elevations occurred early, even with short-term exposure. Given the concern for brain development and growth in hypothyroid children, our results suggest the need for more rigorous pediatric-specific thyroid monitoring guidelines.

Exercise training-induced changes in metabolic syndrome parameters, carotid wall thickness, and thyroid function in middle-aged women with subclinical hypothyroidism

This study analyzed the differences in effects of a 12-week combination of exercise training program with resistance training and aerobic exercises on the risk factors of metabolic syndrome, carotid wall thickness, and thyroid function, between subclinical hypothyroidism patients and obese groups, in middle-aged women. Subjects consisted of either 20 middle-aged women in the subclinical hypothyroidism (SCH) group or 20 obese (body mass indices [BMI], ≥ 25 kg/m²) women without hypothyroidism in the obese (OB) group. The body composition, blood lipid factors, hormones associated with thyroid functions, blood pressure (BP), and carotid intima-media thickness were measured, while physical fitness was ascertained. In the SCH group, waist circumference (WC) and high-density lipoprotein cholesterol values were outside the normal ranges, while WC and systolic BP (SBP) were outside the normal ranges in the OB group. Following the 12-week training program, significantly positive changes occurred in body fat percentage, sit and reach test results, and SBP (p < 0.05) in the SCH group, while in the OB group, significantly positive changes in BMI, WC, sit and reach test results, SBP, and diastolic BP (DBP, p < 0.05) were observed. In addition, both groups showed significant decreases in intima-media thickness of the right carotid bifurcation (p < 0.05). However, in the two groups, the 12-week exercise training program did not have similar significant impact on the hormones related to thyroid functions and blood lipids. Therefore, further research on exercise training that can effectively induce changes in the hormones associated with thyroid functions in patients with subclinical hypothyroidism is necessary.

Hashimoto Thyroiditis and Dyslipidemia in Childhood: A Review

Hashimoto autoimmune thyroiditis (AIT) is the most common cause of acquired hypothyroidism in the pediatric population. Development of AIT is mediated mainly by cellular immune response directed toward thyroid autoantigens, leading to inflammation and impaired function of thyroid gland. Both thyroid dysfunction and inflammation affect the metabolism of plasma lipoproteins. The alterations in lipid profile worsen with the advancement of hypothyroidism, ranging from discrete changes in euthyroid AIT patients, to atherogenic dyslipidemia in the overt hypothyroidism. In this review, characteristics of dyslipidemia in pediatric AIT patients, and the consequences in respect to the risk for cardiovascular disease (CVD) development are discussed. Additionally, benefit of L-thyroxine treatment on serum lipid profile in pediatric AIT patients is addressed. Finally, potential usefulness of novel lipid biomarkers, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), non-cholesterol sterols, low-density lipoprotein particle size and number, and high-density lipoprotein structure and functionality in AIT patients is also covered. Further longitudinal studies are needed in order to elucidate the long-term cardiovascular outcomes of dyslipidemia in pediatric patients with Hashimoto AIT.