Is My Thyroid Function Normal?

What is the Thyroid and How Does it Work?

The thyroid is a butterfly-shaped gland in the neck, just below the Adam’s apple. It produces hormones that regulate how the body uses energy (metabolic rate); as a result, a healthy thyroid is essential for the adequate function of every organ in the body.[1],[2]

The thyroid gland produces two main hormones:[1]

• Thyroxine (T4) accounts for 93% of the hormone secreted by the thyroid. However, it is converted into T3 after entering the organ tissues.
• Triiodothyronine (T3) represents the other 7%. T3 is four times more potent than T4, but it has a lower blood concentration.

Both hormones have the same functions; thus, they work together to regulate the body’s metabolic activity:[1]

• Nutrition: stimulation of carbohydrate, fat, and protein metabolism; this also results in higher appetite and lower body weight.
• Cardiovascular: increase heart rate and strength, maintain normal blood pressure and increase blood flow.
• Respiratory: increase respiratory rate and depth.
• Gastrointestinal: increase intestinal motility and production of digestive juices.
• Muscle function: increase muscular vigour and reaction speed.
• Brain: increase thinking speed.
• Endocrine: promote the production of other hormones.
• Growth and development: regulate growth in children, as well as organ formation and brain development in babies before and after birth.

The thyroid also produces calcitonin, which helps to regulate blood calcium levels by decreasing them when necessary.[1]

A healthy thyroid gland needs iodine and the adequate functioning of the anterior pituitary gland, a small gland in the brain that produces the thyroid-stimulating hormone (TSH). The hypothalamus also plays a role by regulating TSH production; this forms a feedback loop called the hypothalamic-pituitary-thyroid axis.[1],[2]

When the thyroid gland malfunctions, it may become underactive (hypothyroidism) or overactive (hyperthyroidism). Hypothalamus and pituitary disorders may also result in hypo- or hyperthyroidism.[1],[2]

What are the Causes and Symptoms of an Underactive or Overactive Thyroid?

Worldwide, thyroid disorders are caused by low iodine intake, which is common in iodine-deficient areas (in remote and mountainous regions, South-East Asia, Latin America and Central Africa) and leads to an underactive thyroid.[2],[3] In areas with adequate iodine levels, thyroid disorders are mostly related to autoimmune conditions.[3] Thyroid disorders are very common, especially among adult women, but they can affect anyone at any age.[4]

Causes and Symptoms of Hypothyroidism; an underactive thyroid can be caused by:

• Iodine deficiency.[2]
• Autoimmune conditions (atrophic thyroiditis or Hashimoto’s thyroiditis).[2],[5]
• Destructive treatment for an overactive thyroid or other conditions. These include surgical removal of the thyroid (subtotal or total thyroidectomy), radioactive iodine (iodine-131), and external irradiation of the neck.[2],[5]
• Infiltrative conditions, such as haemochromatosis, lymphoma, and sarcoidosis.
• Thyroiditis (inflammation of the thyroid gland). It may lead to high thyroid hormone levels followed by an underactive phase.[5]
• Medications (amiodarone, iron, calcium, thionamides, lithium, among others).[5]

People with hypothyroidism may present a slower metabolic rate, resulting in some of the following symptoms:[6]

• Cold intolerance.
• Fatigue, weakness, muscle pains.
• Dry skin.
• Painful joints (arthralgia).
• Constipation.
• Thin hair/hair loss.
• Memory impairment and slow thinking.
• Depression.
• Weight gain (despite poor appetite).
• Irregular or heavy periods.
• Decreased sexual drive.

During medical consultation, your doctor may encounter the following clinical findings:[6]

• Low heart rate (bradycardia).
• Goitre.
• Hypothermia.
• Hypertension.
• Slow reflexes.
• Swelling (oedema), especially around the eyes.
• Laboratory exams may show:[6]
• High levels of C-reactive protein.
• Low sodium in the blood (hyponatraemia).
• High triglycerides and LDL cholesterol.
• Anaemia.
• Protein loss through the urine (proteinuria).

Causes and Symptoms of Hyperthyroidism; an overactive thyroid (hyperthyroidism) can be caused by:

• Autoimmune conditions, such as Graves’ disease (the most common cause).[3],[4]
• Toxic adenoma and toxic multinodular goitre.[3],[4] The nodules have thyroid tissue that is not regulated by the hypothalamic-pituitary-thyroid axis, increasing hormone production.[7]
• Thyroiditis. It may be caused by infections, autoimmunity, post-partum, etc.[2]
• Excessive thyroxine replacement.[4] It may occur during the treatment of an underactive thyroid.
• TSH-secreting adenoma, a tumour that produces the thyroid-stimulating hormone (TSH).[8]
• Metastatic follicular thyroid cancer.[8]
• Medications (amiodarone, interleukin-2, lithium).[8]
• Gestational hyperthyroidism. It occurs due to high levels of human chorionic gonadotrophin, a hormone secreted during pregnancy that the body may confuse with thyroid hormones.[8]

An overactive thyroid speeds up the metabolic rate of an individual. This may produce a myriad of symptoms, some of the most important are:[8]

• Heat intolerance.
• Weight loss (despite increased appetite).
• Anxiety.
• Excessive sweating.
• Tremor.
• Palpitations.
• Fast speech.
• Eye sensitivity to wind, smoke, and bright lights.
• Pseudodiarrhoea (increased stool frequency).
• Nail separation (onycholysis).

During medical consultation, your doctor may encounter some of the following clinical signs:[8]

• High heart rate (tachycardia).
• Irregular pulse.
• Fast reflexes.
• When suspecting Graves’ Disease, some of the following signs may be encountered:
• Exophthalmos.
• Swelling around the eyes.
• Clubbing of the fingers and toes.
• Swelling of the hands and feet.

In extreme cases, very high levels of T3 and/or T4 may result in a “thyroid storm” (also known as thyrotoxicosis), a potentially lethal medical emergency.[8]

How to Test for Thyroid Function?

Thyroid function is commonly studied through hormone levels and thyroid autoimmunity. Thyroid disorders have varied and relatively non-specific symptoms that can easily confuse patients and doctors; therefore, testing is essential for a trustworthy diagnosis.

Thyroid hormone levels and antibody levels may vary due to age, sex, and technical or regional reasons; always check your report for the current reference ranges and ask your GP if you have any concerns. The reference ranges are:

• TSH: 0.270 – 4.2 mlU/L.
• FT4: 12 – 22 pmol/L.
• FT3: 3.1 – 6.8 pmol/L.

Thyroid Function Test

Assess thyroid function and indicate abnormal thyroid activity.

£59.00

Add to Cart ›

Thyroid Function & Autoimmune Reaction Test

Assess thyroid function and indicate abnormal thyroid immune activity.

£89.00

Add to Cart ›

Thyroid Hormone Testing

Hormone testing usually includes T3 (triiodothyronine), T4 (thyroxine), and TSH (thyroid-stimulating hormone). In the blood, T3 and T4 can be found in two forms: bound to a carrier protein or free; during clinical testing, T4 is usually measured in its free form (free T4 or FT4).[5]

You can test your thyroid health from home with the Vitall Thyroid Function Home Test Kit, which includes:

1. Thyroid Stimulating Hormone (TSH).
2. Free Thyroxine (FT4).
3. Triiodothyronine (FT3).

TSH is the hormone that regulates the thyroid gland, so it tells us a lot about thyroid function. When correlated with T3, T4, and the relevant clinical findings, your doctor will be able to arrive at a preliminary diagnosis:

• Underactive thyroid (hypothyroidism): high TSH and low FT4.[6]
• Subclinical hypothyroidism: high TSH and normal FT4.[6] In these cases, patients may not present overt symptoms of an underactive thyroid.[5]
• Overactive thyroid (hyperthyroidism): low TSH and high T3; T4 levels may be high or normal.[8]
• TSH-secreting pituitary adenoma: high TSH, T3 and FT4. It is rare and requires other tests for confirmation.[8]

Thyroid Autoimmune Testing

Most of the time, hormones levels will help to diagnose thyroid function; however, they cannot determine the most common causes of thyroid disorders in the UK (autoimmune disorders, such as Hashimoto thyroiditis and Graves’ disease). For that reason, Vitall has a test that helps to diagnose these conditions:

The Thyroid Function & Autoimmune Reaction Home Test Kit includes:

• Thyroglobulin Antibodies (TGAB).
• Thyroid Peroxidase Antibody (TPO).
• Thyroid-Stimulating Hormone (TSH).
• Free Thyroxine (FT4).
• Thyroxine (T4).
• Triiodothyronine (FT3).

Alongside hormone levels, TGAB and TPO help to diagnose Hashimoto thyroiditis in patients with hypothyroidism symptoms.[5] The presence of TPO antibodies suggests Graves’ disease (in patients with hyperthyroidism symptoms.[2]

The Importance of Checking Your Thyroid Function Regularly

Each test serves a different purpose, but they hold great value when used correctly.

If you only need to check your thyroid function, thyroid hormone testing is a great option. It may be used to discard the presence of thyroid disorders (and sometimes pituitary disorders) when clinical findings are fuzzy, but you may need autoimmune testing later.

However, if you are already diagnosed with a thyroid disorder, it is important to take a thyroid hormone test regularly, especially during the beginning of your treatment. It helps to fine-tune hypothyroidism medication and avoid under- or overmedication (both can be harmful). A doctor should help you to determine how frequently you have to take the test and when to stop.

On the other hand, if you have clinical signs and symptoms that strongly correlate with a thyroid disorder, you may need autoimmune testing. This test, however, may not need to be repeated as often.

Thyroid Function Test

Assess thyroid function and indicate abnormal thyroid activity.

£59.00

Add to Cart ›

Thyroid Function & Autoimmune Reaction Test

Assess thyroid function and indicate abnormal thyroid immune activity.

£89.00

Add to Cart ›

How to Treat an Underactive or Overactive Thyroid?

Thyroid disorders are commonly treated with medicines, although some conditions may require other types of treatment.[9],[10] You may need to see an endocrinologist before getting a treatment plan.

Hypothyroidism Treatment

An underactive thyroid is commonly treated with levothyroxine, a hormone that replaces thyroxine. It is important to check your hormone levels regularly, and you may need a couple of dose adjustments before finding the right dose. Symptoms may persist for a couple of months.[9]

If you have subclinical hypothyroidism (low hormone levels with minimal or no symptoms), you may not need any treatment; however, your doctor may need to monitor your hormone levels and your symptoms from time to time.[9]

If you are or plan to become pregnant, notify your GP because you may need specialised care.[9]

Hyperthyroidism Treatment

An overactive thyroid can be treated in many ways, depending on the cause and the individual.

• Carbimazole, methimazole and propylthiouracil help to reduce thyroid hormone levels.[8],[10]
• Beta-blockers, such as propranolol or atenolol, help to manage hyperthyroidism symptoms.[8],[10]
• Radioactive iodine treatment helps to destroy an overactive thyroid gland without needing surgery. Symptoms may persist for 2-3 months, and most patients develop hypothyroidism after 2-6 months.[8]
• Surgery may be needed if the other treatments fail or are contraindicated. This surgery removes most or all of your thyroid gland, leading to hypothyroidism.[10]