Subclinical hyperthyroidism is associated with a 20% increased risk for cardiovascular mortality, primarily driven by heart-failure deaths, according to a large study in more than half a million individuals from general practice in Denmark, reported at the 2013 European Congress on Endocrinology.
"The main finding is a 20% increased risk of mortality in all levels of hyperthyroidism, including overt and subclinical but also high-normal, euthyroid patients, those lying in the lower range of the normal thyroid-stimulating hormone [TSH],"
"The take-home message is that if a person has a family history with any thyroid problem or has any signs of thyroid problems, they should go for a checkup. Their family doctors need to be aware that any sign of thyroid abnormality can affect cardiovascular health, and they should act accordingly."
The link between overt hyperthyroidism and cardiovascular mortality is quite well established, he said, but the finding of an association with subclinical hyperthyroid disease is much more novel.
Of 574,595 included individuals (mean age, 48.7 years; 39.1% male), 95.9% were euthyroid, 1603 (0.3%) had overt hypothyroidism, 11,834 (2.1%) had subclinical hypothyroidism, 3967 (0.7%) had overt hyperthyroidism, and 6264 (1.1%) had subclinical hyperthyroidism.