Impact of subclinical hypothyroidism on the coronary artery disease in apparently healthy subjects

ObjectiveCardiovascular disease (CVD) occurs frequently and may progress more rapidly in overt hypothyroidism (OVH). However, the role of mild thyroid failure as a risk factor for CVD is not clear. This study is aimed at exploring the association between subclinical hypothyroidism (SCH) and coronary artery disease (CAD), as detected by cardiac computed tomography (CT), in apparently healthy subjects.Subjects and methodsWe retrospectively enrolled 2404 asymptomatic subjects who underwent cardiac CT with an intermediate to high risk (Framingham 10-year risk ≥10%) of developing CAD but with no known CAD or thyroid disease. Coronary artery calcium score (CACS) was assessed by calcium scan, and the presence of the plaques (CAD), with ≥50% stenosis being indicative of obstructive CAD, was assessed by coronary CT angiography.ResultsOf the 2404 subjects, 2355 subjects were euthyroid (Eu; 53±9 years, 83 females) and 49 had SCH (58±12 years, seven females). CAD and CACS >100 were more prevalent in SCH subjects than in Eu subjects (Eu vs SCH: CAD, 948 (40.6%) vs 31 (63.3%), P=0.002; CACS >100, 239 (10.3%) vs 10 (20.4%), P=0.031). SCH was also an independent risk factor for CAD after a multivariate analysis (odds ratio: 2.125, 95% confidence interval: 1.049–4.307, P=0.036).ConclusionsSCH subjects who were at an intermediate-to-high risk of developing CAD were significantly more likely to exhibit occult CAD than Eu subjects, especially in men with SCH. These findings suggest that mild thyroid failure also independently contributes to the development of CAD.

Thyroid autoimmunity and miscarriage

To ascertain the strength of the association between thyroid autoimmunity and miscarriage, we performed a meta-analysis of both case-control and longitudinal studies performed since 1990 when this association was first described. A clear association between the presence of thyroid antibodies and miscarriage was found with an odds ratio (OR) of 2.73 (95 % confidence interval (CI), 2.20-3.40) in eight case-control and ten longitudinal (OR, 2.30; 95 % CI, 1.80-2.95) studies. This association may be explained by a heightened autoimmune state affecting the fetal allograft, of which thyroid antibodies are just a marker. Alternatively, the association can be partly explained by the slightly higher age of women with antibodies compared with those without (mean+/-S.D. age difference, 0.7+/-1.0 years; P<0.001). A third possibility is mild thyroid failure, as thyroid-stimulating hormone (TSH) levels in antibody-positive but euthyroid women are higher than in antibody-negative women: difference 0.81+/-0.58 mU/l (P=0.005). Randomized clinical trials with l-thyroxine (aiming at TSH values between 0.4 and 2.0 mU/l) and with selenium (to decrease antibodies against thyroid peroxidase) are clearly needed to elucidate further the nature of this association.