BACKGROUND
Subclinical, or mild, hypothyroidism is a common condition where the TSH level is increased but the thyroid hormone levels are normal. Patients with subclinical hypothyroidism often have multiple symptoms, including fatigue and decreased energy. It is unclear whether there are any benefits to treating patients with subclinical hypothyroidism, as often symptoms are not changed with thyroid hormone treatment. This is especially true in the elderly, where some studies have shown that a mildly increased TSH may be beneficial. Further, symptoms attributed to subclinical hypothyroidism can also be caused by other medical problems. One such medical problem is anemia, a condition where red blood cells and/ or hemoglobin are low. Symptoms of anemia often include fatigue, weakness, and decreased energy.

Both subclinical hypothyroidism and anemia are common in the elderly. In addition, prior studies have shown that patients with subclinical hypothyroidism may have lower hemoglobin levels compared to persons with normal thyroid function. It is unclear whether the lower hemoglobin levels are caused by the subclinical hypothyroidism. The aim of this study was to assess whether hemoglobin levels improved after treating subclinical hypothyroidism with levothyroxine in older adults.

THE FULL ARTICLE TITLE
Du Puy RS et al 2022 No effect of levothyroxine on hemoglobin in older adults with subclinical hypothyroidism: Pooled results from two RCTs. J Clin Endocrinol Metab. Epub 2022 Feb 26. PMID: 35218666.

SUMMARY OF THE STUDY
Data for this study were collected from two previously completed clinical trials that were done to explore the effects of treating subclinical hypothyroidism in older adults; the Thyroid hormone Replacement for Untreated older adults with Subclinical hypothyroidism Trial (TRUST) and the Institute for Evidence-Based Medicine in Old Age (IEMO) 80-plus Thyroid Trial. The study included 669 patients with subclinical hypothyroidism divided into 332 patients that were treated with levothyroxine and 337 patients that received a placebo (a dummy pill with no hormone/medication). All participants were ≥ 65 years of age and the average hemoglobin level was 13.8 g/dl. Only 69 participants had anemia at baseline, which was defined as hemoglobin <12 g/dl for women and <13 g/dl for men. As expected, the patients that received levothyroxine had a TSH in the normal range while the placebo group continued to have an increased TSH. The study found that the change in the hemoglobin level was no different between the levothyroxine and placebo groups after 12 months of follow-up. This was true even for patients who had anemia at baseline.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study showed that treatment of subclinical hypothyroidism with levothyroxine in those ≥ 65 years of age did not lead to an increase in hemoglobin levels, regardless of the presence of anemia. These findings have implications for clinical practice as oftentimes patients present with nonspecific symptoms and may incidentally be found to have subclinical hypothyroidism and/or anemia. These results suggest that anemia is not an indication to treat subclinical hypothyroidism. This is particularly important for the older adult population for whom risks of treating mild (subclinical) hypothyroidism can often outweigh the benefits.

— Abdul Karim Arida, MD, and Maria Papaleontiou, MD

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