BACKGROUND
Hypothyroidism is a common medical condition and occurs in about 11% of the US population. Symptoms of hypothyroidism include fatigue, lack of concentration and muscle weakness. Hypothyroidism is diagnosed with an increased TSH and low FT4 levels. Subclinical, or mild, hypothyroidism occurs when only the TSH is abnormal. Treatment may not be necessary for subclinical hypothyroidism. American Thyroid Association guidelines suggests starting treatment for patients who have TSH higher than 10 uIU/mL or selected patients with TSH higher than 5 uIU/mL. Hypothyroidism is treated by replacing the thyroid hormone with levothyroxine taken on a daily basis. The goal of treating hypothyroidism is resolution of symptoms related to the hypothyroidism along with returning the TSH and FT4 level into the normal range.

Unfortunately, many patients on thyroid hormone are not adequately treated and TSH levels may remain abnormal despite being on treatment. It is not clear whether inadequately treated hypothyroidism may cause any complications for patients admitted to the hospital. The current study tries to answer this question. Because TSH and T4 levels may change during hospitalization from reasons other than hypothyroidism (like administered medications or the patient’s sickness), in this study, the TSH and Free T4 levels before admission (when patient was not sick) were used.

THE FULL ARTICLE TITLE
Ettleson MD et al. 2022 Suboptimal thyroid hormone replacement is associated with worse hospital outcomes. J Clin Endocrinol Metab. Epub 2022 Apr 26. PMID: 35472082.

SUMMARY OF THE STUDY
The authors reviewed the medical records of patients who were admitted to their hospital and compared the outcomes between patients with hypothyroidism and without hypothyroidism.

To identify the patient who had hypothyroidism they used the medication list in medical record and diagnostic codes used for ordering laboratory tests. Individuals who were 18 to 64 without a history of thyroid cancer, hyperthyroidism or pituitary problems were included. Patients were divided to groups based on the level of their TSH (low, normal, mildly elevated, and elevated). About 10,000 patients were included in the study. A control group of about 21,000 patients was added.

The low TSH group (over-treated) had no differences in hospital outcomes, as compared with the control group. In the normal TSH group, there was a lower risk of both death during the hospitalization and readmission after discharge. The intermediate TSH group demonstrated no differences in hospital outcomes. However, the high TSH (> 10 uIU/ml, under-treated) group had a higher hospital stay (about 1.2 days) and also had a higher rate of readmission in 30 and 90 days.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study suggests that under-treatment of hypothyroidism resulting in a continued increase in TSH levels may result in a longer hospital stay or even possibly higher rate of readmission. Interestingly, over-treatment or mild under-treatment did not appear to have any differences compared to those patients with normal thyroid function. There results should lead to additional studies to confirm the findings. However, this study provides a preliminary information regarding the importance of adequately treating hypothyroidism.

— Shirin Haddady, MD

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