It is possible to have a mildly underactive thyroid but to not experience any symptoms, or not troublesome ones. This is referred to as subclinical hypothyroidism. Some people alternatively call this borderline thyroid. The term may also be used when the hormones in your blood are deemed adequate in medical terms, but you personally are experiencing symptoms of hypothyroidism. There’s some disagreement on pinning down a definite definition of borderline thyroid between these two distinctions, but most agree that it definitely applies when a blood test reveals raised TSH and normal free T4.

The thyroid is a butterfly-shaped small gland that sits at the front of your neck. It produces important hormones required for multiple different bodily processes. Most particularly, your thyroid affects your metabolism in ways such as influencing your heart rate, use of carbohydrates and fats, body temperature regulation, and protein production regulation. Hypothyroidism is when not enough thyroid hormones are produced and this will disrupt many of these processes.

What is subclinical hypothyroidism

When considering what does borderline thyroid mean, we need to understand subclinical hypothyroidism as this is most likely what is being referred to.

Subclinical hypothyroidism is considered a precursor to a diagnosis of hypothyroidism. It indicates that the thyroid is, to a mild degree, not producing enough thyroid hormones. It’s picked up on a blood test through marginally elevated levels of thyroid stimulating hormone (TSH).

TSH is not produced by the thyroid gland but rather by the pituitary gland. The hormones being produced by the thyroid gland itself are actually still showing as within normal range. So it’s a kind of alarm call, flagging up that there may be a problem looming down the line.  However, generally at this stage the individual isn’t actually experiencing marked symptoms.

What does borderline thyroid mean in the longer term?

Some of those with subclinical or borderline hypothyroidism will go on to develop hypothyroidism. However, not everyone with subclinical hypothyroidism will. The numbers who develop hypothyroidism following a subclinical test result aren’t fully known. One study revealed that as many as 26.8% of those with subclinical hypothyroidism went on to develop hypothyroidism within 6 years. Another study showed it was as low as between 3 and 8%.

What causes subclinical hypothyroidism

It is understood that subclinical hypothyroidism shares the same causes as hypothyroidism itself.

How the thyroid works is a complex process. In essence, it starts with the pituitary gland. This gland, which is found at the base of the brain, is responsible for creating and releasing all sorts of hormones. One of these is called thyroid stimulating hormone (TSH). TSH then goes on to stimulate the thyroid, which is found at the front the neck, to make its own hormones – notably T3 and T4 (amongst others).

If your TSH levels are low it can impact on the thyroid’s ability to manufacture ample amounts of hormones.

Reasons for this are quite varied. They include genetic predisposition, injury, treatment for hyperthyroidism, and taking medications containing iodine or lithium. Women are more likely to develop subclinical hypothyroidism, believed to be due to estrogen. Risk also increases with age.

Does borderline thyroid cause symptoms

For most people, borderline thyroid, or subclinical thyroid, doesn’t cause symptoms. Some people with ‘normal’ blood results can still experience symptoms. Different countries and healthcare systems have different levels which are deemed ‘normal’. If you have hypothyroidism symptoms it is always worth getting medical advice.

If you do develop symptoms of subclinical hypothyroidism they tend to be quite non-specific and very difficult to pin down as being caused by thyroid problems. For example, they include things like fatigue and depression, as well as constipation and weight gain. Of course, these symptoms can exist for those without thyroid difficulties, so it is difficult to ascertain what is what.

You may find it helpful to look at How to tell if you may have a thyroid problem.

If you think that issues with your thyroid may be behind any symptoms you are experiencing, you can request a blood test. The blood result should show a TSH level within the normal range for subclinical hypothyroidism to be discounted. Bear in mind that it is very normal for TSH levels to fluctuate, so multiple repeated tests may be necessary.

Is borderline thyroid treated?

The debate around borderline thyroid extends to how or whether to treat it too. Different healthcare systems have different approaches. This is largely because causing TSH levels to go too high can in itself cause adverse effects. It’s often a very fine balancing act.

If you are experiencing thyroid symptoms, or have subclinical hypothyroidism, your doctor will consider various factors when deciding whether or not to treat it. Of course, they will look at the TSH levels on your blood tests, but they will also look at things like your symptoms (how much it is affecting your life), your age, medical history and whether you have antithyroid antibodies and/or a goiter (swelling of the thyroid gland, visible at the front of the neck).

The main treatment for hypothyroidism is levothyroxine (often sold under the brand names Levoxyl and Synthroid). This is another reason why healthcare professionals can be reluctant to treat subclinical hypothyroism – because it’s a synthetic hormone which may cause problems if too much is taken. There are other natural thyroid treatments which may be considered. Sometimes a physician will begin thyroid treatment to see if it is indeed borderline thyroid causing the problems, and in this case, treatment is usually only for a few months as a kind of test.

Getting help for borderline thyroid

Understanding what borderline thyroid means often comes down to individual interpretation. If you are concerned that you might have subclinical or borderline hypothyroidism, it is essential that you consult your doctor.

At International Pharmacy, we are here to support you with your medication choices. Should you need thyroid medication, you can order though us. However, it is essential that you always follow your doctor’s advice.