1. There was no significant improvement of symptoms associated with subclinical hypothyroidism when subjects aged 80 year or older were given levothyroxine versus the placebo.
Evidence rating: 1 (Excellent)
Study Rundown: Levothyroxine is a known treatment for hypothyroid-related symptoms such as fatigue, constipation, depression and others. However, little is known about the effects of this treatment in adults 80 years and older with subclinical hypothyroidism. In this study, two randomized control trials, namely Institute for Evidence Based Medicine in Old Age (IEMO) and Thyroid Hormone Replacement for Untreated Older Adults With Subclinical Hypothyroidism Trial (TRUST), were pooled together for a comprehensive analysis of the association between levothyroxine and thyroid-related symptoms. The study followed adults aged 80 and over who are found to have elevated levels of thyrotropin upon routine examination but normal free T4 levels. The study demonstrated that levothyroxine is not an effective treatment of subclinical hypothyroidism symptoms in adults aged 80 years and older. Of note, levothyroxine was not linked to any adverse events or secondary outcomes. The study is limited in that the results cannot be applied to all ethnicities almost all participants identified as white. The study also had a small percentage of the participants that stopped complying with the medication regimen, which may have led to some bias in their questionnaire responses.
In Depth [prospective cohort]: In this prospective analysis of two randomized double-blind, placebo controlled parallel-group controlled trials that were conducted between April 2013 and May 2018, a total of 251 participants aged 80 or above were randomized to receive levothyroxine or a placebo. Both trials recruited participants in the Netherlands, Switzerland, Ireland, and/or the United Kingdom, where participants aged 80 and above were recruited based on persistent subclinical presentation of hypothyroidism (elevated thyrotropin level of 4.6 – 19.9 mIU/L). Participants with current medication use of levothyroxine, amiodarone, lithium, or antithyroid medication were excluded from the study. Furthermore, participants with a history of heart failure (as classified by New York Heart Association class IV), dementia, recent acute coronary syndrome, acute myocarditis, or pancarditis and/or a terminal illness were also excluded along with those with a recent hospitalization for major illness or recent thyroid surgery or radioiodine therapy. The participants were followed up for a total of 12 months, for a maximum of 36 months where lab results and surveys were used to compare baseline to the follow up visits. The study had an 84% completion rate, 212 participants completed the trials successfully. The levothyroxine group revealed a total decline of 2.4 (21.7 to 19.3) in hypothyroidism symptoms score taken at baseline compared to 12-months. The placebo group also had a total decline of 2.4 (19.8 to 17.4) in symptom scoring, with an adjusted between-group difference of 1.3 [95% CI, −2.7 to 5.2]; P = 0.53. Overall, the study shows no significant association between levothyroxine treatment and improvement of symptoms related to subclinical hypothyroidism in adults aged 80 years and older.
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