An underactive thyroid (or hypothyroidism) is where your thyroid gland doesn't produce enough hormones.
Although the condition is not always serious (in that it leads to chronic or fatal illness) it can have a massive impact on quality of life.
If it is not treated, an underactive thyroid can lead to complications, including swelling of the thyroid (a condition called goitre), heart disease, mental health problems and infertility, according to the NHS.
According to the British Thyroid Foundation, one in 20 people will have a thyroid condition, so it's important to recognise the symptoms and get help for it.
"An underactive thyroid means your thyroid gland isn’t producing enough thyroid hormone (thyroxine) for your body’s needs," says Gwen Collins, chief nurse at Bupa.
"There are many symptoms of underactive thyroid, but tiredness, weight gain and feeling depressed are common signs. Other symptoms include feeling the cold easily, dry or pale skin, and brittle hair and nails.
What does the thyroid gland do?
The thyroid gland is found in the neck. It produces hormones that are released into the bloodstream to control the body's growth and metabolism. These hormones are called thyroxine and triiodothyronine.
They affect processes such as heart rate and body temperature, and help convert food into energy to keep the body going.
Julia Priestley, development officer at the British Thyroid Foundation adds: "Typical symptoms are fatigue or tiredness, sensitivity to the cold, physical and mental slowness (some people describe this as a "brain fog"), dry skin and hair, low mood or depression and sometimes fertility problems."
What is an underactive thyroid caused by?
“The causes are either because the immune system is attacking your thyroid gland or a damaged thyroid," says Gwen. "Autoimmune thyroiditis, or Hashimoto's disease, is a common type of autoimmune reaction that causes an underactive thyroid.”
Because some of the symptoms for an underactive thyroid are similar to other conditions, it can be frightening not knowing what's happening, if an episode does take place.
Loose Women star Sherrie Hewson spoke to The Daily Mail about her frightening experience, saying that she was "overcome with lethargy" while out walking her dog.
"It happened out of nowhere - as if someone had pulled the plug on me,' she recalls. "One moment I was enjoying my walk near Conway, where I was living at the time, and the next I felt like all the strength was leaking out of me. I was as weak as a kitten. I had pains in my arms and they felt like lead. I was terrified. I just assumed in my panic that I was having a heart attack."
Thyroid UK also has advice on how to bring your diet in line with the condition, and foods you may want to eat in moderation. "Goitrogenic foods can act like an anti-thyroid drug in disabling the thyroid function. They prevent the thyroid from using available iodine. Coffee may interfere with thyroid hormone absorption."
These foods are:
- Brussel sprouts, swede, turnips, cauliflower, cabbage and kale
- Almonds, peanuts and walnuts
- Sweetcorn, sorghum and millet
What are the treatments available if you do happen to have it?
Most likely, as Sherrie found out, you will need treatment for life, probably hormone-replacement tablets, called levothyroxine, will raise your thyroxine levels.
Thyroxine is a hormone (body chemical) made by the thyroid gland in the neck. It is carried round the body in the bloodstream. It helps to keep the body's functions (the metabolism) working at the correct pace. Many cells and tissues in the body need thyroxine to keep them going correctly.
Gwen adds: "If you do have an underactive thyroid, your doctor may prescribe you hormone-replacement medicine. This helps return your levels of thyroid hormones to normal. However, if your symptoms are mild, you might not have to take any medicine, but your doctor will keep a close eye on your hormone levels in case you need to start.”
For more information, visit the British Thyroid Foundation.