The Newcastle University research shows it is worth having thyroid levels checked, because thyroid disease is easily identified and treated. It affects up to 16 percent of women and 6 percent of men, and becomes more prevalent with age.

Known medically as subclinical hypothyroidism, it is characterized by a shortage of the hormone thyroxine and often precedes an underactive thyroid.

The study, published in The Journal of Clinical Endocrinology and Metabolism, showed that treatment of subclinical hypothyroidism with thyroid hormone reduces tiredness, cholesterol and reduces the risk factors for heart disease by improving the markers of arteriosclerosis or hardening of the arteries.

"The results of our study show that treatment of people with this mild form of underactive thyroid condition leads to significant improvements in risk factors for ischemic heart disease and symptoms of tiredness," Dr. Jolanta Weaver, of Newcastle University's School of Clinical Medical Science, said in a statement.