Echocardiographic evaluation of left ventricular diastolic dysfunction in subclinical hypothyroidism: A case-control study

Effect of thyroid hormone replacement treatment on cardiac diastolic function in adult patients with subclinical hypothyroidism: a meta-analysis

Background

Although subclinical hypothyroidism (SCH) is related to abnormalities in left ventricular diastolic function, the use of levothyroxine as a regular treatment remains debatable. This meta-analysis aimed to determine whether thyroid hormone replacement therapy affects cardiac diastolic function in patients with SCH as measured by echocardiography.

Methods

This meta-analysis included a search of the EMBASE, PubMed, Web of Science, and Cochrane Library databases from their inception to May 18, 2023, for studies analyzing cardiac morphology and functional changes in patients with SCH before and after thyroid hormone replacement. The outcome measures were cardiac morphology and diastolic and overall cardiac function, as assessed using ultrasound parameters (including ventricular wall thickness, chamber size, mitral wave flow, tissue Doppler, and speckle tracking). The quality of the studies was assessed using the Newcastle-Ottawa Scale. The standard mean differences (MDs) and 95% confidence intervals (CI) were calculated using fixed- or random-effects models.

Results

Seventeen studies met the inclusion criteria. A total of 568 patients participated and completed the follow-up. All studies specifically stated that serum thyrotropin levels returned to normal by the end of the study period. Compared with baseline levels, no significant morphological changes were observed in the heart. In terms of diastolic function, we discovered that the ratios of E-velocity to A-velocity (E/A) had greatly improved after thyroid hormone replacement therapy, whereas the ratios of the mitral inflow E wave to the tissue Doppler e' wave (E/e') had not. Global longitudinal strain (GLS) increased significantly after treatment with levothyroxine.

Conclusion

In adult patients with SCH, thyroid hormone supplementation can partially but not completely improve parameters of diastolic function during the observation period. This meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 statement, an updated guideline for reporting systematic reviews (11) and was registered with INPLASY (INPLASY202320083).

Systematic review registration

https://inplasy.com/inplasy-2023-2-0083.

Assessment of subclinical hypothyroidism for a clinical score and thyroid peroxidase antibody: a comparison with euthyroidism grouped by different thyroid-stimulating hormone levels

Background

Subclinical hypothyroidism (SCH) might have many symptoms of hypothyroidism. The controversy appears to lower the level of thyroid-stimulating hormone (TSH) and group subjects with TSH of more than 3 or even 2.5 mIU/L as SCH subjects.

Objectives

To assess SCH subjects both clinically using Zulewski clinical score and biochemically and to evaluate whether the euthyroid subjects with high-normal TSH (HNT) have any clinical symptom or subnormal biochemical finding.

Methods

A prospective cross-sectional study of 233 subjects, 67 with SCH and 166 euthyroidism, was conducted. Euthyroid subjects were divided according to the level of TSH as HNT (>2.5 mIU/L) and low-normal TSH (0.5–2.5 mIU/L). The subjects were examined for clinical feature including Zulewski clinical score and biochemical evaluations including thyroid peroxidase antibody (TPO-Ab) titer. The comparisons between groups were assessed using independent sample t test, and correlations between variables were evaluated using Pearson correlation.

Results

A significantly higher clinical score and higher frequencies of symptoms were found in the SCH group compared to the euthyroid group. The most frequent symptom was fatigue. Euthyroid subjects with HNT were found to have higher TPO-Ab titers than those with low-normal TSH, P < 0.05. The Zulewski clinical score was positively correlated with TSH and TPO-Ab titer but negatively correlated with the FT4 level, P < 0.05.

Conclusions

Zulewski clinical score is higher in SCH subjects compared to euthyroid subjects and can aid in assessing SCH subjects. A significant correlation exists between Zulewski clinical score and each of the TSH, FT4, and TPO-Ab titer levels. The frequency of TPO-Ab positivity is high in SCH. Additionally, euthyroid with higher TSH levels has higher level of TPO-Ab titer but not higher clinical score.

The Change of Left Ventricular Function in Rats with Subclinical Hypothyroid and the Effects of Thyroxine Replacement

OBJECTIVE

The main purpose of this study was to explore the relationships between serca2a, Ryr2, adipokines, and the left ventricular function in the subclinical hypothyroidism with different TSH levels and to determine the impact of L-T4 treatment on these indexes.

METHODS

Sixty-five male Wistar rats were randomly divided into five groups: control group; sHT A, B, and C group; and sHT + T4 group. The sHT rats were induced by methimazole (MMI), and the sHT + T4 rats were administered with L-T4 treatment after 8 weeks of MMI administration. Serum TT4, TSH, APN, chemerin, and TNF-α were detected by radioimmunoassay kits and ELISA kits; left ventricular function was measured by PowerLab system via subclavian artery catheter. The expression of Serca2a, Ryr2, APN, chemerin, and TNF-α were detected by RT-PCR, Western blot, and immunohistochemistry.

RESULTS

The sHT groups had significantly higher TSH, chemerin, and TNF-α and lower Serca2a, Ryr2, and APN. The left ventricular pressure and heart rate in sHT groups were significantly lower in control and sHT + T4 group. Histopathological examination revealed the pathological changes in the sHT rats' heart. L-T4 administration reduced TSH level and improved left ventricular function.

CONCLUSIONS

TSH can impair left ventricular function by regulating several factors, and L-T4 treatment ameliorates it in sHT rats.