Thyroid Hormone Levels

The thyroid is an ‘endocrine’ gland located in the neck which produces two hormones. These hormones, thyroxine and triiodothyronine, regulate how fast cells work, which is also known as your ‘rate of metabolism’. So, your thyroid hormone levels are important for controlling the activity of your cells.

If your thyroid hormone levels are too high, it can be a sign of hyperthyroidism (overactive thyroid). And if they’re too low, it can be a sign of hypothyroidism (an underactive thyroid).

Thyroid disorders are very common and usually affect more adult women than men. But, anyone can be affected, including men, babies, and children. It’s estimated around 1 in 20 people worldwide have a thyroid disorder.

Your thyroid can be found at the front of your neck just underneath your Adam’s apple. The thyroid is made up of two lobes lying on either side of your windpipe.

The standard ranges for thyroid hormone levels are:

• Thyroid stimulating hormone (TSH): 0.4 - 4 milliunits per litre (mU/L)
• Free thyroxine (T4): 9.0 - 25.0 picomoles per litre (pmol/L)
• Free triiodothyronine (T3): 3.5 - 7.8 picomoles per litre (pmol/L)

But, each lab that tests for thyroid hormone levels may use slightly different units to record thyroid hormone levels. In this example it’s picomoles per litre but it can also be others, like milliunits per litre.

The body has a natural feedback system which works to make sure our thyroid hormone levels are within the normal ranges. However, if this system isn’t working properly, it can cause hyper- or hypothyroidism.

For example, if thyroid hormone levels fall, more thyroid stimulating hormone (TSH) will be released by the pituitary gland in the brain. TSH controls the amount of T4 and T3 produced by the thyroid gland. Equally, if too much of these hormones are produced, the release of TSH will stop.

If your thyroid hormone levels are low it may be a sign of an underactive thyroid. Symptoms include:

• Tiredness (fatigue)
• Weight gain
• Feeling cold
• Depression
• Constipation
• Muscle aches, cramps, and weakness
• Dry, scaly skin
• Brittle hair
• Loss of sex drive (libido)
• Slow movements
• Pain, numbness or tingling in hands and fingers
• Irregular or heavy periods

If your thyroid hormone levels are low, your thyroid isn’t producing enough of these hormones and so your metabolism may be slow. In other words, your cells are working more slowly which is why you may experience these symptoms.

Hypothyroidism can be caused by an underlying autoimmune disease, where your own immune system attacks your body, called Hashimoto’s Thyroiditis. This disease causes your own immune system to attack your thyroid gland, which then stops the release of thyroid hormones that your body needs for metabolic processes.

The signs and symptoms of an underactive thyroid or Hashimoto’s Thyroiditis may not develop until later into the condition. So, it’s possible to have hypothyroidism and not be showing any symptoms.

If left untreated, hypothyroidism can:

• increase your risk of cardiovascular disease
• cause an abnormal swelling of the thyroid gland, which is called a goitre
• in rare cases, cause a coma

It can also lead to pregnancy complications, like:

• Anaemia in the mother
• Pre-eclampsia
• Birth defects
• Bleeding after birth
• Stillbirth or miscarriage
• Premature baby

If your thyroid hormone levels are high, this can be a sign of an overactive thyroid. Symptoms include:

• Anxiety
• Irritability
• Nervousness
• Mood swings
• Difficulty sleeping
• Increased heart rate
• Weight loss
• Twitching
• Swelling in the neck called a goitre
• Heat sensitive
• Fatigue

These symptoms occur because your thyroid gland is producing too much of the thyroid hormones, so your cells are working at a faster rate than normal.

An overactive thyroid can be caused by:

• Graves’ Disease – an autoimmune condition where the immune system attacks the thyroid
• Thyroid Nodules – benign lumps on the thyroid gland causing an overproduction of thyroid hormones
• Medication – iodine-containing medication can cause the thyroid to overproduce thyroid hormones

There are a few complications associated with an overactive thyroid.

Eye problems:

• Watery eyes
• Feeling dry and gritty
• Red eyes
• Bulging eyes
• Sensitivity to light

Pregnancy issues:

• Pre-eclampsia
• Premature birth
• Miscarriage
• Low birthweight

An underactive thyroid is also a possible complication related to having an overactive thyroid because it can often happen as a result of getting overactive thyroid treatment.

Thyroid storm – this can occur if the overactive thyroid is undiagnosed or poorly controlled. It can be triggered by:

• Infection
• Trauma
• Pregnancy
• Not taking medication as directed

You can request a blood test from your GP. In this case, it’ll usually be a full blood test, where a sample will be taken from a vein in your arm.

At ZAVA, we also offer a blood test kit for checking your thyroid hormone levels (TSH and T4) at home. This is how it works:

• We’ll send you a test kit for you to use at home, which you’ll get within 1 to 2 days of placing your order
• You’ll need to provide a small blood sample and use the pre-paid envelope we provide in the kit to post it to our partner lab
• Your results will be ready 2 to 3 days after your sample reaches the lab. At that point, we’ll let you know when they can be viewed in your account

Levothyroxine

The typical treatment for an underactive thyroid is a daily hormone replacement in the form of a tablet called ‘levothyroxine’.

Levothyroxine replaces the hormone your thyroid isn’t making enough of. Usually, you’ll need regular blood tests to figure out the right dose, which means it can take a while to get right.

Levothyroxine is taken once per day. You should take your pill at the same time every day, ideally in the morning. You should swallow them with water and wait half an hour before eating. This is because the effectiveness of levothyroxine can be affected by food, supplements, or other types of medication.

Combination Therapy

Combination therapy isn’t a popular choice of treatment in the UK because there’s a lack of evidence to support that it’s better than levothyroxine alone.

Combination therapy uses levothyroxine and triiodothyronine (T3) together. It may be recommended if someone has a history of thyroid cancer.

There are three main treatments for an overactive thyroid:

• Medication
• Radioiodine treatment
• Surgery

Medication

The medication used to treat an overactive thyroid are called ‘thionamides’, which stop the thyroid from producing excess hormones.

The main types are:

• Carbimazole
• Propylthiouracil

These types of medication can have side effects, including:

• Nausea
• Headaches
• Upset stomach
• Aching joints
• Itchy rash

When your hormone level is under control, your dose may be reduced and even eventually stopped. However, some people need to take the medication for the rest of their lives.

Radioiodine

Using radiation can be very effective at stopping your thyroid from producing high levels of hormones.

Radioiodine is:

• highly effective
• given in drink or capsule form
• absorbed by your thyroid to stop it over-producing thyroid hormones
• usually only required once

With radioiodine, it can usually take up to a few months for you to feel the full benefits of the treatment.

Surgery

Surgery to remove your thyroid may be right for you if:

• you have a goitre (your thyroid gland is swollen)
• your overactive thyroid is causing eye problems
• medication or radioiodine isn’t right for you
• your symptoms return after trying medication or radioiodine

If you’re experiencing any symptoms like those associated with a hypo- or hyperactive thyroid, you should consider a thyroid test.

If you have a thyroid test and your results are abnormal you should speak to your GP as soon as possible to discuss starting treatment.