TSH, the pituitary hormone that signals the thyroid, is the test we use to check whether thyroid replacement is at the right dose. A number alone does not give the whole picture, and the evidence on treating mildly abnormal results in older adults is more mixed than many people expect. This article explains what we measure, what the TRUST trial found, and why we recheck after each change.
TSH is the test we use
For patients on levothyroxine, we use TSH to see whether the dose matches what the body needs. In the 2021 crossover trial, TSH stayed within the reference range on all three treatments, which is how that comparison was kept fair (Shakir 2021).
Decisions also use the patient’s history and symptoms. TSH is a measurement, not a complete diagnosis on its own.
Subclinical hypothyroidism in older adults
Subclinical hypothyroidism means a raised TSH with a normal free T4. In the TRUST trial, 737 adults aged 65 and older with subclinical hypothyroidism took levothyroxine or placebo for one year. The between-group difference in the hypothyroid symptom score was 0.0 points (95% confidence interval -2.0 to 2.1), and the authors concluded that levothyroxine provided no apparent benefit (Stott 2017).
Recheck after every dose change
We recheck TSH about six to eight weeks after any change in dose, because levothyroxine takes weeks to settle in the blood. We do not judge a dose by one early result, and we do not change it again until the next recheck shows the effect.
What TSH cannot tell you
- A normal TSH does not guarantee that you feel well. Persistent symptoms are a reason to look at other causes too.
- A raised TSH in an older adult without symptoms may not need treatment, as the TRUST result suggests.
- Taking more thyroid hormone than you need can cause symptoms of an overactive thyroid, and we do not adjust doses to lose weight. Thyroid hormone is not a weight-loss treatment.
Desiccated thyroid and T3 change the picture
Even when TSH stays in range on T3 or desiccated thyroid, as it did in the 2021 trial, symptoms and preference still need checking. A normal TSH alone does not show how a patient feels on a given product.
How we use this
Our physicians confirm the diagnosis with labs, recheck TSH after each dose change, and do not treat a borderline number in an older adult without symptoms on the number alone. We do not use thyroid hormone for weight loss.
Explore weight loss treatmentsSources
- 1.Guidelines for the Treatment of Hypothyroidism: prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement Jonklaas J et al., Thyroid, 2014
- 2.Thyroid Hormone Therapy for Older Adults with Subclinical Hypothyroidism (TRUST) Stott DJ et al., N Engl J Med, 2017
- 3.Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism Shakir MKM et al., J Clin Endocrinol Metab, 2021