A study by Newcastle University researchers shows that thousands of people who go untreated for a common chronic condition could actually be treated safely.

At the moment, people with mild thyroid failure, a condition also known as subclinical hypothyroidism (SCH), are frequently not given treatment. This is partly because of long-term safety concerns about the treatment, thyroid hormone replacement, which has the potential to cause heart problems particularly when taken at higher doses.  In fact, this study shows that younger people who were given the treatment had significantly fewer heart problems.

Today, the Newcastle and Gateshead doctors have published the first large-scale analysis of the long-term health of people with mild thyroid failure. The study analysed the health of more than 4000 people from the UK General Practice Research Database over 7 years from their first blood test showing the diagnosis of SCH.

“The most important finding was that long-term treatment with levothyroxine hormone replacement appears to be very safe in this condition” said Dr. Salman Razvi, Senior Lecturer in Endocrinology at Newcastle University’s Institute for Genetic Medicine. “In fact, the younger patients who received treatment had significantly fewer heart problems over the course of the study, when compared to those whose doctors had decided not to treat them.”

Current clinical practice guidelines don’t recommend routine treatment of mild thyroid failure, despite the fact that up to 6% of UK women are affected, and that there is a 50% increase in the risk of heart problems in people with the condition.

One reason for this, is that rather like high blood pressure or high cholesterol, many people have no symptoms from the problem. Another reason why treatment is not currently recommended is safety concerns about long-term thyroid hormone replacement. A particular heart rhythm problem, atrial fibrillation (AF), is a well known effect of too much thyroid hormone, but this was found to occur at the same rate in SCH patients whether they were treated with levothyroxine or not. In fact, in younger patients, less heart problems were observed in those who received the levothyroxine.

“The safety data is compelling, but we now really need a large randomised trial to confirm that there are heart benefits for those SCH people who take levothyroxine” said Dr. Razvi.

Patients with SCH tend to have rather vague symptoms, such as lethargy, sleepiness or a lack of clear thinking. However, as only about half of SCH patients with such symptoms will feel better with levothyroxine treatment, and there were previously concerns about its safety, currently many doctors don’t start such people on treatment.

Janis Hickey, Founder and Director of the British Thyroid Foundation, a patient-led charity, said “'This is an important study that emphasises the need for further investigation to fully understand the effects of levothyroxine treatment on heart disease so that subclinical hypothyroidism can be managed appropriately and patients can benefit from appropriate treatment.”

Mrs Fowler, of Rowlands Gill, said: “I work as a fitness instructor and found that I was unable to do my job properly due to the tiredness. Levothyroxine has made a difference – I have more energy, feel more positive, and my mood is also better. I am pleased to learn that more people will now be offered treatment”.

The full citation details Razvi S, Butler T, Weaver J, Pearce S, Arch Intern Med 2012; doi:10.1001/archinternmed.2012.1159.

published on: 23 April 2012