http://archinte.jamanetwork.com/ en-us Mon, 28 May 2012 00:00:00 GMT Tue, 01 Jan 2013 00:47:53 GMT Silverchair editor@archinte.jamanetwork.com webmaster@archinte.jamanetwork.com http://archinte.jamanetwork.com/article.aspx?articleID=1149638 Mon, 28 May 2012 00:00:00 GMT Burman KD. <span class="paragraphSection">Subclinical hyperthyroidism is defined as a patient having normal free thyroxine (FT₄) and total triiodothyronine (T₃) levels in conjunction with a thyrotropin (TSH) level persistently below the normal range in the absence of factors known to suppress TSH. Factors that may alter TSH value and thyroid function test results include medications such as corticosteroids and dopamine and clinical conditions to include hypothalamic or pituitary hypofunction and nonthyroid illness. Nonthyroid illness is a general term that applies to a wide variety of patients who have systemic illness that can result in altered thyroid function test results. In general, the diagnosis of subclinical hyperthyroidism is made in ambulatory outpatients who are not taking medications known to affect thyroid function. The incidence of subclinical hyperthyroidism is approximately 1%. The most common causes of endogenous subclinical hyperthyroidism include Graves disease (usually younger patients), multinodular goiter (typically older patients), and solitary autonomous nodules. The discrimination between endogenous hyperthyroidism from exogenous hyperthyroidism is important, since exogenous hyperthyroidism can usually be treated by modulation of the levothyroxine dose. Although the study by Collet et al focuses on cardiovascular effects, subclinical hyperthyroidism is also associated with an increased risk of osteopenia and/or osteoporosis, especially in older women, which may improve following treatment of the hyperthyroidism. It is controversial whether cognitive function is altered by the presence of subclinical hyperthyroidism.</span> 172 10 809 810 10.1001/archinternmed.2012.1114 http://archinte.jamanetwork.com/article.aspx?articleID=1149638 http://archinte.jamanetwork.com/article.aspx?articleID=1149640 Mon, 28 May 2012 00:00:00 GMT Collet T, Gussekloo J, Bauer DC, et al. <span class="paragraphSection"><div class="boxTitle">Background</div>Data from prospective cohort studies regarding the association between subclinical hyperthyroidism and cardiovascular outcomes are conflicting. We aimed to assess the risks of total and coronary heart disease (CHD) mortality, CHD events, and atrial fibrillation (AF) associated with endogenous subclinical hyperthyroidism among all available large prospective cohorts.<div class="boxTitle">Methods</div>Individual data on 52 674 participants were pooled from 10 cohorts. Coronary heart disease events were analyzed in 22 437 participants from 6 cohorts with available data, and incident AF was analyzed in 8711 participants from 5 cohorts. Euthyroidism was defined as thyrotropin level between 0.45 and 4.49 mIU/L and endogenous subclinical hyperthyroidism as thyrotropin level lower than 0.45 mIU/L with normal free thyroxine levels, after excluding those receiving thyroid-altering medications.<div class="boxTitle">Results</div>Of 52 674 participants, 2188 (4.2%) had subclinical hyperthyroidism. During follow-up, 8527 participants died (including 1896 from CHD), 3653 of 22 437 had CHD events, and 785 of 8711 developed AF. In age- and sex-adjusted analyses, subclinical hyperthyroidism was associated with increased total mortality (hazard ratio [HR], 1.24, 95% CI, 1.06-1.46), CHD mortality (HR, 1.29; 95% CI, 1.02-1.62), CHD events (HR, 1.21; 95% CI, 0.99-1.46), and AF (HR, 1.68; 95% CI, 1.16-2.43). Risks did not differ significantly by age, sex, or preexisting cardiovascular disease and were similar after further adjustment for cardiovascular risk factors, with attributable risk of 14.5% for total mortality to 41.5% for AF in those with subclinical hyperthyroidism. Risks for CHD mortality and AF (but not other outcomes) were higher for thyrotropin level lower than 0.10 mIU/L compared with thyrotropin level between 0.10 and 0.44 mIU/L (for both, P value for trend, ≤.03).<div class="boxTitle">Conclusion</div>Endogenous subclinical hyperthyroidism is associated with increased risks of total, CHD mortality, and incident AF, with highest risks of CHD mortality and AF when thyrotropin level is lower than 0.10 mIU/L.</span> 172 10 799 809 10.1001/archinternmed.2012.402 http://archinte.jamanetwork.com/article.aspx?articleID=1149640