Like people who have hypothyroidism, those who have no symptoms of an underactive thyroid also have an increased risk of coronary heart disease. In a recent meta study combining the results of 14 observational studies, researchers at the University of Lausanne, Switzerland found:

Subjects with an underactive thyroid without symptoms, also referred to as subclinical hypothyroidism, had a 65 percent increased risk of coronary heart disease.
Nine studies included a comparison group without hypothyroidism, matched to the hypothyroid group for age and demographic factors — those with subclinical hypothyroidism had an increased risk of 81 percent for heart disease.
In studies that …read more

Over at The Medical Blog Network, Dr. Rob Lamberts gives an overview of risk factors for coronary heart disease.

Diabetes – especially Type 2 (Adult onset) diabetes
High blood pressure
Family history of heart disease (Father under age 55, mother under age 65 or siblings with heart disease are considered strong risk factors)
Smoking – the more the merrier – smoking a single cigarette per day is not the same as 2 packs per day, but both are a bad idea.
High Cholesterol.

Learn more at Dr. Lamberts’s blog.