Treatment of subclinical hypothyroidism with the medication levothyroxine appears to be related to fewer ischemic heart disease events in younger patients but this finding was not evident in older patients, according to a report published Online First in Archives of Internal Medicine.
Subclinical hypothyroidism (SCH) is defined as an elevated serum thyrotropin level in the presence of normal thyroid hormone concentrations. The condition is relatively common and often asymptomatic, although recent meta-analyses have suggested that SCH is associated with increased cardiovascular events and death, especially in young to middle-aged adults, the authors write in their study background. But those epidemiologic associations do not prove that treatment of SCH would be effective, the authors note.
"Thus, only adequately powered randomized controlled intervention trials will be able to demonstrate whether treatment of SCH is worthwhile in terms of improvement in both cardiovascular disease risk and symptoms. However, such a trial has not been performed to date and no such trials are ongoing," they comment.
Salman Razvi, M.D., F.R.C.P., of Gateshead Health National Health Service Foundation Trust and Newcastle University, England, and colleagues used the United Kingdom General Practitioner Research Database to indentify patients with new SCH recorded during 2001 with outcomes analyzed until March 2009. SCH was identified in 3,093 younger patients (40-70 years) and 1,642 older patients (older than 70 years). Levothyroxine was used to treat 52.8 percent of younger patients and 49.9 percent of older patients.
The study results indicate there were 68 incident IHD events among 1,634 younger patients treated with levothyroxine (4.2 percent) vs. 97 events among 1,459 untreated individuals (6.6 percent). In the older group there were 104 events among 819 treated patients (12.7) percent vs. 88 events among 823 untreated patients (10.7 percent).
"In conclusion, treatment with levothyroxine was associated with fewer IHD events and reduced all-cause mortality during an eight-year period of observation in 40 to 70-year-old individuals with SCH but not in those who were older. A prospective randomized controlled trial is required to confirm these findings," the authors conclude.
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Arch Intern Med. Published online April 23, 2012. doi:10.1001/archinternmed.2012.1159