Too Much of a Good Thing: Subclinical Hypothyroidism vs Heart Disease

To follow up yesterday's post regarding subclinical hyperthyroidism, I thought I'd point out a study published early online on the same day earlier this week in Archives of Internal Medicine but regarding the treatment of subclinical hypothyroidism.  Specifically, the authors defined subclinical hypothyroidism as a thyrotropin level of 5.01-10mIU/L w/normal free thyroxine levels and followed 3,093 40-70yo & 1,642 older than 70yo for over 7yrs.  

Among the younger crowd (average age 56yo), those who received levothyroxine had a 39% lower relative risk of ischemic heart disease compared to those who went untreated.  More impressively, there was a 64% lower relative risk of all-cause mortality, the gold standard of outcome trials.  However, in the older group (average age 80yo), there was not statistically significant relationship between levothyroxine and heart disease.

Before you consider asking your family physician for treatment (or consider offering this to your patients), ask if you (they) are similar to the participant demographics in this study (after all, this is part of what it means to practice evidence-based medicine - what works for mice & flies won't necessarily work for you & me).  

Bottom line: as this was a not a randomized controlled trial, it can only offer us some very tempting hypotheses. However, we still need to perform a rigorous RCT in order prove cause & effect, especially in the old old.  In the meantime, think long & hard about what this study means to your patients today.

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