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

It affects up to 16% of women and 6% of men, becoming more prevalent with age.

The research has shown that treatment of subclinical hypothyroidism with thyroid hormone reduces tiredness, cholesterol and reduces the risk factors for heart disease by improving the markers of atherosclerosis or hardening of the arteries.

In the study, patients undergoing 12 weeks of thyroxine treatment saw a reduction in their amount of LDL cholesterol, reversed weight gain - losing on average half a kilo, felt less tired and had reduced their risk factors for heart disease.

Until recently many doctors considered this condition not worthy of treatment. Now a new study led by Dr Jolanta Weaver of Newcastle University and Gateshead NHS Foundation Trust published in this month's issue of The Journal of Clinical Endocrinology and Metabolism shows that treatment leads to significant improvements for patients.

In the largest trial to date, 100 participants with persistent subclinical hypothyroidism were given thyroxine and compared with those taking a placebo or dummy medication.

Dr Salman Razvi and Dr Jolanta Weaver of Newcastle University's School of Clinical Medical Sciences carried out a pivotal crossover study. They assessed common heart disease risk factors such as the level of LDL, or "bad", cholesterol, body weight and endothelial function, which is a very early marker of hardening of the arteries. They also asked participants to rate their quality of life.

This treatment did not cause any side-effects.

Dr Weaver says, "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."

Patients with subclinical hypothyroidism are being encouraged to discuss their treatment with their doctors.

Source: University of Newcastle upon Tyne