Subclinical hypothyroidism (SCH) is mild thyroid failure. It happens when the thyroid – an important gland governing your metabolism – isn’t working properly.

Here we look at how to know if you have subclinical hypothyroidism, the symptoms you may experience, and whether SCH needs treating.

Do I have subclinical hypothyroidism?

Picking up thyroid problems is relatively easily done by looking at specific levels of certain hormones in a blood test.

In subclinical hypothyroidism, the hormone levels aren’t significant enough to diagnose hypothyroidism, but they may be causing symptoms in the patient. Looking at the blood results, it becomes apparent that they have ‘normal’ results for peripheral thyroid hormone levels, but slightly elevated results for thyroid stimulating hormone (TSH). 80% of people with this kind of mild thyroid failure have TSH results of less than 10 mIU/L.

It’s actually remarkably common, occurring in 3% to 8% of the population, but not everyone experiences symptoms.

Generally speaking, subclinical hypothyroidism is more common in women. It is more common as you get older. There is concern about subclinical hypothyroidism, firstly because it may cause difficult symptoms, but also it may lead to clinical hypothyroidism. Some patients may benefit from hormone replacement treatment, such as levothyroxine.

Why is it important to understand subclinical hypothyroidism?

It’s important that your thyroid gland is functioning optimally. It is responsible for many different processes in the body and can affect heart and brain health, and all functions affected by your metabolism. Subclinical hypothyroidism can produce unwanted symptoms in some people and also indicate that the individual may go on to develop full-blown hypothyroidism.

The causes of subclinical hypothyroidism are exactly the same as the causes and predisposition for thyroid problems. These include a family history of autoimmune thyroid disease, thyroid injury, and too much iodine.

Are there symptoms of subclinical hypothyroidism?

Many people live with subclinical hypothyroidism and can be symptom-free. If your TSH levels are only marginally elevated then this is more likely.

However, some people with subclinical hypothyroidism do experience symptoms. This can be very difficult, firstly because the symptoms can be difficult to define and explain, and secondly, because they can be easily dismissed by medical professionals because of the subclinical test results.

Common symptoms of subclinical hypothyroidism include depression and low mood, fatigue, lack of energy, constipation and weight gain. Some people find they have intolerance to cold, or get cold easily. Hair loss is another symptom. Although the symptoms may be non-specific, they can greatly affect your quality of life.

Diagnosis of subclinical hypothyroidism

As said, a blood test is the easiest way to diagnose subclinical hypothyroidism. However, while there are ‘normal’ ranges that doctors use to understand thyroid test results, what constitutes normal can vary from country to country. Additionally, there is debate amongst the thyroid and medical community that the normal range is potentially set too high – hence patients are experiencing symptoms even when their results are supposedly within range.

In order for patients not to feel dismissed or overlooked, and so they don’t continue struggling with symptoms, all medical professionals should be aware of taking a personalized approach to subclinical hypothyroidism. It’s also important to repeat blood tests regularly to pick up small changes.

There are also some small amounts of evidence showing that untreated subclinical hypothyroidism may lead to heart problems such as high cholesterol and high blood pressure. Subclinical hypothyroidism has also been associated with pregnant women experiencing miscarriage.

Should subclinical hypothyroidism be treated?

Again, there is considerable debate about when to start treatment for patients with subclinical hypothyroidism. Generally, if it isn’t causing symptoms then treatment may not be necessary and it is just a case of doing regular blood tests to determine if and when clinical hypothyroidism occurs.

However, for those with subclinical hypothyroidism experiencing symptoms and with TSH levels above 5.1 mIU/L, it is generally considered beneficial to start thyroid medication. Your doctor will consider multiple factors including your blood results, symptoms, medical history and age.

Levothyroxine is the most common form of treatment for subclinical hypothyroidism.

It is also important to consider the individual’s diet in cases of subclinical hypothyroidism. This is because too little or too much iodine can cause hypothyroidism. Iodine is found in marine fish, dairy products, eggs and iodized table salt. A well-balanced diet is usually sufficient.

What should I do if I think I have subclinical hypothyroidism?

If you suspect that you may have subclinical hypothyroidism, you should first arrange a blood test. If, on receiving these results, you are told that your results are in the normal range, ask for the actual results. You can then use these to see if they put you in the subclinical range.

If your blood test results show subclinical hypothyroidism and you are experiencing symptoms (or struggling to maintain a pregnancy), then your medical professional should take a personalized approach to your treatment. As explained, the debate about subclinical hypothyroidism is hot in the medical profession, so if your GP is unsympathetic, it may be beneficial to seek a second opinion.

Usually, within a short period of time taking hormone replacement medication, like levothyroxine, the symptoms of subclinical hypothyroidism go away.

The information given here is accurate at the time of publication to the best of our knowledge. However, please bear in mind that it is provided for information only and you should seek individual medical advice from your own healthcare professional.