What is an underactive thyroid?
Underactive thyroid function, also known as hypothyroidism, is a condition when your thyroid gland doesn’t make or release enough thyroid hormone into your bloodstream. This slows down your metabolism and can cause unwanted symptoms like weight gain or feelings of fatigue, and over time it can also lead to other health conditions.
But how do you know if you have an underactive thyroid? In this article, we explore what are the symptoms of an underactive thyroid and how you can find out more about your thyroid function with private thyroid function blood tests.
What is hypothyroidism?
Hypothyroidism or underactive thyroid is a condition that occurs when your thyroid gland doesn’t produce or release enough hormone into your bloodstream. This causes your metabolism to slow down and can lead to unintentional weight gain and fatigue.
Often, these symptoms come on gradually, and many people put it down to just getting older. However, as the condition progresses and the metabolism continues to slow down, you may start to develop more obvious problems.
Types of hypothyroidism
There are four main types of hypothyroidism: primary, secondary, tertiary, and subclinical hypothyroidism. Below, we explore each in more detail:
Primary hypothyroidism
Primary hypothyroidism is the most common type of hypothyroidism and directly impacts your thyroid gland, causing it to make low levels of thyroid hormones. As a result, your pituitary gland makes more thyroid-stimulating hormone (TSH) to try and compensate for the shortfall. Find out more about TSH and the role it plays in your health in our article ‘What is TSH?’
Autoimmune conditions like Hashimoto’s disease can cause primary hypothyroidism, or it can occur after thyroid gland surgery or radiation therapy.
Secondary hypothyroidism
Secondary hypothyroidism is much rarer than primary hypothyroidism. It occurs when you have an underactive pituitary gland, so it can’t send enough TSH to your thyroid gland to signal it to produce adequate thyroid hormones.
Tertiary hypothyroidism
Tertiary hypothyroidism happens when your hypothalamus, a part of the brain that controls many bodily functions, doesn’t make enough thyrotropin-releasing hormone (TRH). This in turn, means that your pituitary gland can’t make enough TSH and causes underactive thyroid function.
Subclinical hypothyroidism
Subclinical hypothyroidism, also known as mild thyroid failure, happens when you have slightly elevated TSH levels, but all other thyroid hormone levels are within range. Subclinical hypothyroidism usually resolves itself within three months.
What are the symptoms of an underactive thyroid?
Hypothyroidism symptoms usually develop slowly and can often get overlooked or put down to ageing, so being aware of the symptoms to watch out for is key. Generally, weight gain and fatigue are the earliest symptoms, but as the condition develops, you may also notice:
- Increased sensitivity to cold
- Brain fog
- Elevated cholesterol levels
- Constipation
- Dry skin
- Weight gain
- Puffy face
- Hoarse voice
- Coarse hair and skin
- Muscle weakness
- Muscle aches, tenderness and stiffness
- Irregular menstrual cycle or heavier periods than normal
- Thinning hair
- Slowed heart rate, also known as bradycardia
- Depression
- Memory problems
If you are experiencing any of these symptoms, it’s important to get your thyroid function checked to find out if underactive thyroid function could be the underlying cause.
What causes hypothyroidism?
Hypothyroidism can be caused by:
- Hashimoto’s disease, an autoimmune disorder, which is one of the most common causes of hypothyroidism
- Certain medications, including lithium, thalidomine and amiodarone
- Conditions present at birth, such as being born without a thyroid gland
- Iodine deficiency
- Pituitary gland disorders, which can include non-cancerous tumours
- Thyroiditis – inflammation of the thyroid that can occur after a viral illness or pregnancy
What are the risk factors for hypothyroidism?
Although anyone can get hypothyroidism, you’re more likely to develop the condition if you are female or if you have:
- An autoimmune disease
- A family history of the condition
- Had thyroid surgery
- Pregnancy
- Previous history of head and neck radiation therapy
- Starting or stopping certain medications
How common is hypothyroidism?
Hypothyroidism is a relatively common condition and affects approximately 2 in every 100 people in the UK.
Although an underactive thyroid can be a lifelong condition for some, it can be treated with hormone replacement therapy. Levothyroxine is the most common medication used to replace the hormone that your thyroid can’t make, but levels require frequent monitoring to ensure that you are on the correct dosage.
How is hypothyroidism diagnosed?
If you’re wondering, ‘Do I have an underactive thyroid?’ you may be keen to learn more about how hypothyroidism is diagnosed.
If you are experiencing symptoms of an underactive thyroid, a thyroid function blood test can help provide insights into your thyroid health. There are numerous different thyroid function blood tests available, but the most used tests to diagnose underactive thyroid function are a TSH blood test and a T4 blood test.
TSH blood test
A TSH blood test measures thyroid-stimulating hormone (TSH) in your blood. A high TSH level indicates your thyroid gland is not making enough thyroid hormone, while a low TSH level indicates your thyroid is producing too much thyroid.
Free T4 blood test
Free T4 (FT4), more commonly known as thyroxine, is the active form of thyroid hormone circulating in the blood. A FT4 specifically measures levels of FT4 in your blood.
Elevated TSH and low FT4 levels can indicate primary hypothyroidism due to disease in the thyroid gland, while low TSH and low FT4 levels indicate primary hypothyroidism due to a problem with the pituitary gland.
Abnormal thyroid results
If your thyroid function blood test results are abnormal, you may be advised to have further tests, such as an ultrasound, CT scan or a thyroid uptake scan, to help confirm the underlying cause of underactive thyroid.
Private thyroid tests from Bluecrest Wellness
At Bluecrest Wellness, our private thyroid function test evaluates the health and functionality of your thyroid gland. This comprehensive test offers insights into both your TSH and FT4 levels as imbalances in these hormones can indicate thyroid disorders, such as underactive thyroid function.
You can book a private thyroid blood test at locations across the UK at a time to suit you. Plus, you can be confident that we will deliver fast, efficient and accurate results as we have established links with leading UK laboratories and are fully accredited for a wide range of private blood checks.
