The change in thyroid function categories with time in patients with subclinical hypothyroidism: a systematic review and meta-analysis.

Xueqi Zhang, Guofeng Zhang, Songwen Wang, Jing Jin, Shimiao Zhang, Xiaochun Teng

Journal: BMC endocrine disorders 2024;24(1):224

PMID: 39456045

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Plain Language Summary

Subclinical hypothyroidism (SCH) is a form of thyroid dysfunction where the serum levels of thyroxine and/or triiodothyronine are within the reference range, while the level of thyroid-stimulating hormone (TSH) is slightly elevated. The primary aim of this study was to evaluate the changes in thyroid function categories over time in patients with SCH, assessing the rates of progression to overt hypothyroidism and remission. This research is a systematic review of 8 studies involving 1,859 participants, synthesising data from multiple longitudinal studies that tracked thyroid function in patients with SCH over varying periods. Results showed that many patients maintained persistent SCH (45.4%) or returned to euthyroidism [normal thyroid function] (44.4%) during the study period, while 10.1% of patients progressed to hypothyroidism. Authors concluded that the vast majority of SCH patients can maintain their disease status or return to the normal range of TSH during follow-up. TSH≥10mU/L and TPOAb-positive were risk factors for disease progression in SCH patients, while gender was not related to the natural outcome of SCH patients.

Abstract

BACKGROUND

Subclinical hypothyroidism (SCH) is characterized by elevated levels of thyroid hormone (TSH) and normal levels of free thyroxine (FT4). The outcomes of SCH patients are crucial for determining treatment plans; therefore, our aim is to summarize the existing prospective studies to understand the changes in thyroid function over time in SCH patients and the factors influencing these changes, providing references for clinical diagnosis and treatment.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science for prospective follow-up studies on natural outcomes of SCH published until September 2024. Results are presented as the overall risk ratio (RR) and 95% confidence intervals (CI).

RESULTS

We reviewed 8 prospective follow-up studies involving 1,859 individuals and extracted data from them for a meta-analysis. We found that when TSH levels are ≥ 10 mU/L, patients with SCH are more likely to progress to overt hypothyroidism (OH) (RR11.38, 95%CI 4.98-26.03, P<0.001) and were less likely to return to normal TSH levels (RR 0.20, 95%CI 0.09-0.42, P<0.001) compared to patients with TSH between 4.5 and 9.9 mU/L. In addition, patients who test positive for thyroid peroxidase antibodies (TPOAb) are more likely to progress to OH (RR 2.53, 95% CI 1.86-3.44, P < 0.001) and less likely to return to euthyroidism (RR 0.68, 95% CI 0.60-0.76, P < 0.001) compared to TPOAb-negative patients.

CONCLUSION

The results indicated that a large proportion of patients diagnosed with SCH will return to normal TSH levels or maintain SCH. Additionally, patients with TSH levels ≥ 10 mU/L or positive for TPOAb are more likely to experience progression and should be closely monitored. However, we did not find any gender differences in the natural outcome of SCH.

Address: Department of Endocrinology and Metabolism, Institute of Endocrine, NHC Key Laboratory of Diagnosis and Treatment of Thyroid Diseases, The First Hospital of China Medical University, Shenyang, 110001, People's Republic of China.; Department of Endocrinology and Metabolism, Institute of Endocrine, NHC Key Laboratory of Diagnosis and Treatment of Thyroid Diseases, The First Hospital of China Medical University, Shenyang, 110001, People's Republic of China. [email protected].

DOI: 10.1186/s12902-024-01754-7