You may have heard of the common condition of hypothyroidism, also known as an underactive thyroid.

But what exactly is the thyroid, what causes it to be underactive, and what effects might it have on your body?

What is the thyroid?

The thyroid is a gland in the neck, shaped like a butterfly, which regulates the hormones associated with regulating the body’s metabolism.

A lack of these hormones, triiodothyronine and thyroxine, can cause many of the body’s normal functions to slow down.¹

What causes hypothyroidism?

The most common reason behind an underactive thyroid (hypothyroidism) is an autoimmune disease, where the body attacks the thyroid, thinking it is made up of foreign cells.

Some medical treatments can also induce hypothyroidism, including:

• some treatments for thyroid cancer
• an overdose of anti-thyroid drugs (usually given for an overactive thyroid)
• medicines such as lithium and amiodarone
• large amounts of iodine can change the way the thyroid functions (found in some cough medicines and some health foods, e.g. kelp)
• a problem with the pituitary gland²

An underactive thyroid is usually diagnosed in those aged over 60.

Hypothyroidism in men is less common than in females – as many as 1 in 5 women have the condition by the age of 60.

One of the reasons for this is that it can be brought on by pregnancy.³

Treatments for hypothyroidism

Once you have been diagnosed with hypothyroidism, the most common treatment is to go on a prescription medication called levothyroxine (synthetic thyroxine), which helps the thyroid to behave normally.⁴

Although you will likely be on this medication for life, once the drug reaches the correct levels in your bloodstream, your symptoms should be reduced and your quality of life should improve.⁵

The best underactive thyroid diet

While there is no single food that is the best food for thyroid patients, there are some dietary considerations that it is important to know about.

Anyone suffering with an underactive thyroid should avoid eating too many soy products, including soy milk, tofu, soy sauce and many processed vegan foods.⁶

Six symptoms of hypothyroid

There are many signs and symptoms of hypothyroidism, but the NHS groups them into six major categories, which will be explored below.⁷

Additionally, it is worth knowing that there are other thyroid symptoms in women who are pregnant, such as anemia, miscarriage, low birth weight and other developmental problems.⁸

1. Depression and other brain changes

Hormones affect the ways your brain works. If your body lacks those hormones normally produced by the thyroid, it can result in depression, along with many associated symptoms of depression.

These include slow speech, movements and thoughts; problems with memory and concentration.⁹

2. Fatigue

Tiredness and fatigue are very commonly found in people with an underactive thyroid.

Fatigue is closely linked with depression: it may be hard to differentiate one from the other at times.

3. Weight gain

Hypothyroidism weight gain is a classic symptom, as the disorder wreaks havoc on the metabolism.

 However, as lifestyle factors also play a huge part in becoming overweight, it is important not to place too much hope on shedding the pounds once you are on treatment.

Working with a nutritionist or dietician might be your best hope for health, long-term weight loss.¹⁰

4. Feeling the cold more

If you notice you are suddenly becoming more sensitive to the cold, even in summer, this could be an indication of hypothyroidism.

Again, it is to do with the way your metabolism is regulated by the hormones produced in the thyroid.

5. Dry skin and hair

Changes in the quality of your skin and hair could be a symptom of an underactive thyroid, especially if coupled with any of the other symptoms.

If you are not metabolising food in the way you should, your body could be missing out on vital nutrients that nourish your skin and hair.

6. Muscle cramps and aches

If you have noticed more regular muscular aches, pains, cramps or weakness, it could be a sign of an underactive thyroid.

Make sure to see your GP and report any combination of the above signs and symptoms that you might be experiencing, so you can get tested.

In addition to the most common symptoms, the British Thyroid Foundation list several other signs and symptoms of an underactive thyroid, including:

• hoarse voice
• constipation
• pins and needles
• heavier, longer periods
• fertility problems
• low libido
• puffy face, especially under eyes
• slow heartbeat
• slightly high blood pressure
• raised cholesterol levels¹¹