With 123 million prescriptions in 2016, levothyroxine tops the charts as America’s most-prescribed drug. 1 But a growing stack of research suggests this super-popular thyroid medication could also be one of the nation’s most over-prescribed pills—particularly for older adults and women with subclinical hypothyroidism, a slightly sluggish thyroid that may or may not contribute to low energy, depression, weight gain and thinning hair.
Subclinical hypothyroidism is defined as a thyroid stimulating hormone (TSH) level of 4.6 to 10 mIU/L. A normal TSH level is 0.4 to 4.0 and full-blown hypothyroidism is 10 or higher. Researchers are finding that treating subclinical hypothyroidism— especially in people with no symptoms or without other indications that treatment may be a good idea (such as a high risk for heart disease)—isn’t helpful and could even be harmful. Yet prescriptions for this group are on the rise. In one 2014 study2 from the UK’s University of Cardiff, researchers found that 31% of people with mild hypothyroidism who got levothyroxine in the United Kingdom between 2001 and 2009 had no symptoms or other indications for a prescription.
“There is evidence of substantial overuse of levothyroxine,” Mayo Clinic endocrinologists note in the April 2017 issue of The Lancet Diabetes & Endocrinology. This could impose “a substantial economic and treatment burden on millions of people,” they conclude. 3 Here are three things to know about taking thyroid hormone for subclinical hypothyroidism:
#1: Subclinical hypothyroidism often improves on its own. Out-of-whack thyroid test results may be a temporary blip, not your new normal. The evidence: In a 2007 Israeli study of 422, 242 women and men, 62% of those whose TSH levels were within the range for subclinical hypothyroidism—a TSH of 5.5 to 10 mlU/L in this study—saw levels return to normal within five years or less. 4 Natural ups and downs in TSH levels could explain it. Illnesses, stress and some medications can all temporarily raise levels, too. What you can do: Rather than starting on medication right away, have a slightly abnormal TSH level rechecked in three to six months to confirm you have subclinical hypothyroidism, recommends the Mayo Clinic endocrinologists. Currently, they say, one in three people with a slightly sluggish thyroid gets a prescription based on just one TSH test.
#2: Subtle symptoms may not be your thyroid’s fault. Taking thyroid hormone just because your TSH levels are slightly inside the subclinical hypothyroidism range may not pep you up—or deliver any other real benefits. Up to one in four people with normal thyroid function have problems like fatigue, dry skin, constipation, weight gain and menstrual-cycle irregularities, too. 5 The evidence: In a recent study from Scotland’s University of Glasgow of 737 older adults with subclinical hypothyroidism, those who took levothyroxine for a mildly sluggish thyroid didn’t feel any less tired or any more mentally sharp than those who didn’t get medication. “We should accept treatment of older subjects with mild subclinical hypothyroidism (TSH 4.6-10) is not justified on basis of current evidence,” lead author, David Stott, MB ChB, MD, told EndocrineWeb when the study was published. What you can do: If you don’t have symptoms and aren’t at risk for more serious thyroid problems, think twice before starting thyroid hormone therapy if your TSH level is between 4.6 and 10. The American Thyroid Association and American Association of Clinical Endocrinologists advise doctors to tailor decisions about treatment for each individual patient in this situation. 6
#3. Give levothyroxine a test drive before you make a long-term commitment. In addition to costing you money, adding this drug to your daily routine can be inconvenient and could be harmful. The evidence: You may have to change your daily routine so you can take your pill 30-60 minutes before a meal. You may need more blood tests to check your TSH levels and more doctor visits to review the results. That’s crucial. In that 2014 UK study, one in 20 people with subclinical hypothyroidism who took thyroid hormone ended up with suppressed thyrotropin levels five years later. That can raise risk for bone fractures and off-beat heart rhythms. What you can do: In that study, 90% of people who started thyroid hormone with subclinical hypothyroidism took it for the long haul. The researchers say the need for the drug is “rarely reviewed” once treatment begins. Talk with your doctor about starting with a low dose of an inexpensive, generic levothyroxine formula— and going back as recommended to assess whether you’re getting benefits.
1. “Medicines Use and Spending in the U.S. A Review of 2016 and Outlook to 2020.” QuintilesIMS Institute, May 2017. Accessed August 18, 2017. URL: https://structurecms-staging-psyclone.netdna-ssl.com/client_assets/dwonk/media/attachments/590c/6aa0/6970/2d2d/4182/0000/590c6aa069702d2d41820000.pdf?1493985952
2. “Falling threshold for treatment of borderline elevated thyrotropin levels-balancing benefits and risks: evidence from a large community-based study.” Taylor PN et al. JAMA Intern Med. 2014 Jan;174(1):32-9. https://www.ncbi.nlm.nih.gov/pubmed/24100714
3. “Levothyroxine overuse: time for an about face?” Rodriguez-Gutierrez R et al. Lancet Diabetes Endocrinol. April 2017, vol. 5, no 4, pp. 246-248. http://www.british-thyroid-association.org/sandbox/bta2016/rodriguez_gutierrez_lancet_diabet_endo_2017__2_.pdf
4. “Serum thyrotropin measurements in the community: five-year follow-up in a large network of primary care physicians.” Meyerovitch J et al. Arch Intern Med. 2007 Jul 23;167(14):1533-8. URL: http://jamanetwork.com/journals/jamainternalmedicine/fullarticle/412896
5. “The Colorado thyroid disease prevalence study.” Canaris GJ et al. Arch Intern Med 2000; 160: 526–34. http://jamanetwork.com/journals/jamainternalmedicine/fullarticle/415184
6. “Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association.” Garber JR et al. Endocr Pract. 2012 Nov-Dec;18(6):988-1028. http://journals.aace.com/doi/10.4158/EP12280.GL?url_ver=Z39.88-2003&rfr_dat=cr_pub%3Dpubmed&rfr_id=ori:rid:crossref.org&code=aace-site