The little gland at the front of your neck, about the same shape and position of a bow tie, is constantly balancing how fast your body ticks over. Too much and you go into overdrive; too little and your world becomes sluggish.
Hormones are 'chemical messengers', produced in one part of your body and released into the blood to have an effect on one or more other parts. Your thyroid gland releases a hormone called thyroxine - this sets the level of your metabolism. It affects the rate your body burns energy by acting on many cells and organs in your body.
But like many hormones, it's usually kept in check by a 'feedback' mechanism. Your brain detects low or high levels of thyroxine, and sends out more or less of another chemical called thyroid-stimulating hormone (TSH), which controls how much thyroxine your thyroid gland produces.
But not understood?
Sometimes your thyroid gland escapes from this feedback control. The most common reason is an 'autoimmune' condition - your immune system, which usually helps you fight off infection, starts thinking your thyroid gland is an 'intruder' and attacks it. As a result, your thyroid gland can produce too much or too little thyroxine. About 1 in 50 women and 1 in 1,000 men will develop an underactive thyroid at some point, and a similar number will have an overactive thyroid.
You're more likely to get thyroid disease if you have other autoimmune conditions like type 1 diabetes, coeliac disease or the skin-bleaching condition vitiligo. If you've had an overactive thyroid in the past you're at higher risk of having an underactive thyroid later in life.
What does underactive thyroid cause?
The symptoms of an underactive thyroid all relate to your body ticking over more slowly. You may put on weight despite not eating more; feel tired and sluggish; have constipation, dry skin, fluid retention and lifeless hair; feel depressed; or sometimes be confused, have a hoarse voice or have problems with periods.
Symptoms can be vague and are often put down to the stresses of modern life. Depression can also cause tiredness and weight or appetite changes, so the two can be confused. It's important to have these symptoms checked out. The first thing I do when someone complains to me of tiredness is to test for underactive thyroid, as well as anaemia, type 2 diabetes and other conditions.
A simple blood test (for thyroxine and TSH) will usually tell if your thyroid gland is underactive. Once you have a diagnosis, you'll need to take thyroxine tablets to top up your body's low levels. At about six weeks on tablets, your doctor will retest your thyroid levels and adjust your dose - the usual dose is 50-150 micrograms a day. You'll need to take replacement treatment for life, but once your levels are stable you should only need a blood test once a year. You'll be entitled to free prescriptions for life.
What happens if your thyroid is overactive?
With an overactive thyroid your whole body speeds up. You may feel hot, sweaty, trembly or anxious; lose weight for no obvious reason; have diarrhoea, shortness of breath or palpitations; and struggle to sleep. While hot flushes and night sweats are common around menopause, if you are also experiencing these other symptoms, get your thyroid checked.
You may also notice problems concentrating, bulging eyes or a lump over your thyroid, called a goitre. These symptoms develop over weeks or months and you may not have them all. It's important to have any of these symptoms checked out - untreated, overactive thyroid can lead to abnormal heart rhythms or heart failure.
What's the treatment?
A blood test will diagnose overactive thyroid. The usual first step in treatment is a tablet called carbimazole - your doctor will monitor your blood carefully to see if the dose needs adjusting. You may also need beta-blockers in the short term to relieve your symptoms while the carbimazole starts to work.
In the longer term, radioactive iodine or surgery may be suggested. Overactive thyroid often settles within a couple of years, but can recur or can become underactive in later life. There are several treatment options for overactive thyroid, all with different side effects. Take time to discuss them with your specialist.
With thanks to 'My Weekly' where this article was originally published.