BACKGROUND: Thyroid hormones (THs) exert multiple biological roles including 
effects on the cardiovascular system (lipid profile, blood pressure (BP) and 
cardiac output). The lipid-lowering actions of TH are mediated by the TH 
receptor-β whereas the mechanisms explaining the BP variations concomitant with 
the thyroid disorders are less understood. As the TH receptor-α (TR-α) has been 
associated with many of TH actions on the cardiovascular system in mice models, 
we hypothesized that it could be involved in the latter. We thus tested whether 
polymorphisms in TR-α (THRA gene) could be associated with BP level variation. 
Secondarily, we tested for association with coronary heart disease (CHD) risk.
METHODS: We analyzed the associations between five THRA polymorphisms and (i) BP 
level in two population-based studies (MONICA Lille n = 1,155; MONICA Toulouse n 
= 1,170) and (ii) the risk of CHD in two case-control studies (Lille CHD n = 558 
cases/568 controls; PRIME n = 527 cases/584 controls).
RESULTS: Individuals carrying the rs939348 T allele had higher systolic BP 
(~+1.3 mm Hg) than CC individuals in both the MONICA Lille (P = 0.02) and 
Toulouse (P = 0.03) studies. The odds ratio (OR) for hypertension was 1.25 (P = 
0.02) in the combined sample. Concerning the CHD risk, no significant 
association could be detected.
CONCLUSIONS: For the first time, our study showed associations between the THRA 
rs939348 polymorphism and systolic BP and the risk of hypertension but not with 
CHD, although we admit that the statistical power available to study any 
relationship with CHD was very limited. Further larger association studies are 
needed to confirm our findings.