Subclinical Hypothyroidism Balancing Act: Knowing When to Treat

Tyler C. Drake, MD


October 03, 2019

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We have an older man with subclinical hypothyroidism of at least 2 years' duration (likely longer) with a stable TSH level and no obvious symptoms of hypothyroidism. Although such patients are often treated with levothyroxine, a 2017 study showed no apparent benefit from treatment with levothyroxine in adults aged 65 years and older.[2] Participants in this study were required to have two separate elevated TSH values at least 3 months and less than 3 years apart. Of 2647 patients with biochemical subclinical hypothyroidism who were screened for inclusion, 62% had reversion of TSH levels to the normal range on repeat testing.

Our patient is similar to this study population, and there is no expected clinical benefit with levothyroxine treatment. A repeat TSH level test in 1-2 years should be considered to monitor the patient for progression to overt hypothyroidism, but it is not required any earlier. TPO antibodies could be checked, but the results would not change the clinical decision in an older patient with stable subclinical hypothyroidism. Of importance, the TSH level upper limit of normal naturally rises with age,[3] and it has been suggested that the upper limit of normal for patients aged 70 and older should be 7.0 mU/L.

Case #2: A Young Woman With a Family History

A 25-year-old woman is concerned that she may have a problem with her thyroid and is requesting laboratory testing. She reports fatigue, dry skin, and cold intolerance, which have all been present for years but worsened over the past 4 months. Her only medication is an oral contraceptive, and she would like to begin having children in the next 3-5 years. Her mother and sister are taking levothyroxine, and she wonders if she should also be receiving the medication. Her blood work reveals an elevated TSH level of 8.5 mU/L (normal range, 0.4-4.5 mU/L) and a normal free T4 result.


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