Spotlight on... thyroid disease: hypothyroidism
In readiness for Thyroid Awareness Week (19th - 25th October), Lyn Mynott explains all about hypothyroidism including what it is, how it is diagnosed and the treatments available. She also gives some ideas on how pharma can help those diagnosed with hypothyroidism.
Thyroid disease is a medical condition impairing the function of the thyroid. The thyroid is found in the neck and controls metabolism. Thyroid hormones control how much energy our cells use and as well as help to regulate our body temperature and play a role in making proteins.
There are two main types of this disease; hypothyroidism (the underproduction of the thyroid hormones) and hyperthyroidism (the overproduction of the thyroid hormones).
This article takes a look into hypothyroidism, while a second follow-up article will explore hyperthyroidism and will be published on the 8th October.
What is hypothyroidism?
Hypothyroidism is the term given when the thyroid produces less thyroid hormone than it should. Other names for this are myxoedema or an underactive thyroid.
Thyroid physiology is complex. The thyroid is part of the endocrine system. The pituitary produces a hormone called thyroid stimulating hormone (TSH) which stimulates the thyroid to produce thyroxine (T4). Thyroxine is inactive and needs to be converted by the tissues and organs of the body into the active hormone, tri-iodothyronine (T3).
Subclinical hypothyroidism is the term used when patients have symptoms of hypothyroidism but only the TSH is abnormal.
What causes hypothyroidism?
Primary hypothyroidism is caused by problems with the thyroid gland:
• Genetic dysfunction: the thyroid may be dysfunctional at birth or is programmed to fail at some time in adult life – there is now evidence of a faulty gene (DIO2)
• Hashimoto's disease: The most common form of hypothyroidism. This is the autoimmune form of hypothyroidism where antibodies attack and destroy the thyroid hormone producing cells
• Thyroiditis: inflammation of the thyroid gland (postpartum and subacute / chronic)
Secondary hypothyroidism is caused by problems outside of the thyroid gland:
• Nutritional – vitamin and mineral deficiencies (iron, selenium, iodine)
• Pituitary or hypothalamic failure – this can be caused by a head injury, tumours or radiation treatment for brain tumours
• Environmental challenges – endocrine disrupters
• Drugs such as Lithium, Amiodorone, contrast media and anti-thyroid drugs
• Thyroid surgery or radioactive iodine treatment
• Inability to absorb synthetic thyroxine adequately
• Lack of conversion from thyroxine to tri-iodothyronine
• Receptor resistance – very rare
Who is at risk?
The incidence of (overt) hypothyroidism is 2% women and 0.2% men. The incidence of subclinical hypothyroidism is 6-8% women and 3% men. The incidence of pregnant women who will develop hypothyroidism is 2.5%.
"Hypothyroidism is most common in women of around 60 years of age..."
Hypothyroidism is most common in women of around 60 years of age and symptoms are often ignored during the early stages by both patients and doctors.
What are the symptoms to look out for?
Signs and symptoms of hypothyroidism can come on very slowly over a period of time. These include:
• Weight gain
• Slow movements, thought and speech
• Pins and needles
• Breathlessness
• Dizziness
• Palpitations
• Loss of libido
• Dry / gritty eyes
• Hoarse voice
• Difficulty swallowing
• Hair loss on head and body
• Dry skin
• Muscle and joint pain
• Loss of appetite
• Constipation
How is hypothyroidism diagnosed?
The tests available to diagnose thyroid disease are:
• TSH – Thyroid Stimulating Hormone
• FT4 – Thyroxine
• FT3 – Tri-iodothyronine
• TPO Ab –Anti-thyroid Peroxidase Antibody
• TgAb – Anti-thyroglobulin Antibody
• TSI – Thyroid Stimulating Immunoglobulin
However, the TSH test is often the only test performed by doctors, which means there is a possibility that autoimmune hypothyroidism and secondary hypothyroidism may be missed.
"Research has shown that symptoms of subclinical hypothyroidism improved with treatment."
A level of FT4 below the reference range together with a TSH level above the reference range will usually give a diagnosis of hypothyroidism. Treatment in the UK is indicated if the TSH is >10 or if symptoms of hypothyroidism are present. If thyroid antibodies are present, subclinical hypothyroidism carries a greater risk of progression to overt hypothyroidism.
Subclinical hypothyroidism is diagnosed when the patient has elevated TSH levels with normal FT4 levels. Research has shown that symptoms of subclinical hypothyroidism improved with treatment.
DIO2 genetic test
The test to diagnose the faulty DIO2 gene is relatively new and is not available on the NHS at present.
What treatment is available?
The most common treatment for hypothyroidism is levothyroxine, which replaces the thyroxine that the thyroid gland is not producing. Most people feel better on this medication. However, some 5 - 10% of patients continue to have symptoms on this treatment.
The addition of liothyronine has been studied in patients, but the results have been inconclusive. Although in some of the studies patients preferred it, there was no overall objective evidence of benefit in terms of symptom scores or other physiological markers.
However, recent research has shown that patients with the faulty DIO2 gene had worse baseline General Health Questionnaire (GHQ) scores than those without the faulty gene and improved on liothyronine.
There are now guidelines on the use of levothyroxine plus liothyronine to help endocrinologists in the experimental use of liothyronine for patients who remain ill on levothyroxine.
Natural desiccated thyroid (NDT) is a treatment that was used before the manufacture of levothyroxine and liothyronine. Research has shown that some patients do very well on this treatment if they have remaining symptoms.
NDT is not a licensed drug as it was manufactured before licensing came into being. It is approved in the United States of America and Canada and can be prescribed on the NHS on a "named patient" basis. Most doctors are not aware of this medication until their patients bring it to their attention. The doctor must write "For hypothyroidism" on the prescription.
How can pharma better support patients with hypothyroidism?
Numbers of patients being diagnosed with hypothyroidism have continually risen over the years. More research needs to be done to find out the reason that hypothyroidism is so prevalent and also the reason some patients only respond well to particular thyroid medications.
"Numbers of patients being diagnosed with hypothyroidism have continually risen over the years."
Patients should be kept on the same brand / generic levothyroxine. If patients are given a different brand / generic, thyroid blood tests should be done to check that their levels do not change significantly.
Recent problems with the withdrawal of some generic brands of levothyroxine and the availability of the raw active ingredient in the only brand of liothyronine manufactured in the UK have caused huge problems for patients and doctors alike.
Measures need to be put in place to ensure that patients can obtain the thyroid medications that they need without any problems.
Patients need more choice of dosages of thyroid medications rather than needing to cut their tablets in half, which is not advisable.
If pharma and thyroid patients could work together more, a lot could be learnt from both sides.
The second part to this article, "Spotlight on thyroid disease: hyperthyroidism", can be viewed here.
About the author:
Lyn Mynott is Chair / Chief Executive of Thyroid UK and has been campaigning for change in the diagnosis and treatment of thyroid disease since 1998.
Thyroid UK is an independent charity providing information and resources to promote effective diagnosis and appropriate treatment for people with thyroid disorders in the UK.
Thyroid UK promotes public awareness of thyroid disorders and encourages scientific research for the education, alleviation, care, treatment and cure of thyroid disease. The number of beneficiaries has increased significantly from its beginnings and this has resulted in a corresponding and substantial growth in the range of services provided.
Tel: 01255 820407
Email: enquiries@thyroiduk.org
Website: www.thyroiduk.org
How can we raise further awareness of thyroid diseases?
