Thyroid gland

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Dr Noureen Ahmad

General Practitioner Belgium

Thyroid diseases are present due to iodine deficiencies as iodine is an essential element for the production of thyroid hormones. In resource-rich countries, food is already fortified with iodine and thus autoimmune thyroid diseases are more common here.

The thyroid is a gland located in the front of the neck which is responsible for synthesising thyroid hormones (T3 and T4). These hormones are essential for the growth and function of the basal metabolism in our body. 

In the brain, the hypothalamus produces the TRH-hormone which orders the pituitary gland to stimulate the thyroid. The pituitary gland then produces a hormone called TSH, which binds to the thyroid and regulates the synthesis of the thyroid hormones. When an imbalance of this regulation occurs, it leads to abnormal regulation of the synthesis of these hormones and this can lead to either hypothyroidism (an underactive thyroid) or hyperthyroidism (overactive thyroid).

Both conditions can lead to a goitre, an enlargement of the thyroid gland. Hypothyroidism is more common than hyperthyroidism and both will be discussed separately in this article.

According to statistics in 2017, hypothyroidism affects 2% of the UK population and of these, 5% of patients are aged above sixty. Women have 5-10 times more chance of developing hypothyroidism than men. 

Hypothyroidism in resource-poor countries is mostly caused due to iodine deficiency, whilst in the UK it is usually caused by an autoimmune disorder – Hashimoto’s disease. In this disease antibodies are formed against the proteins TPO (thyroid peroxidase) which are essential for the synthesis of the thyroid hormones. 

Other causes of hypothyroidism can be a history of thyroid surgery or the use of thyroid destructive medication. These patients can present themselves with symptoms of weight gain, tiredness, hard stool, dry skin and depression. 

The diagnosis of hypothyroidism is made on the clinical symptoms together with a blood test for checking the TSH, T4, T3, TPO antibodies (Hashimoto’s disease). Usually TSH is above the normal range and T3 and T4 are below the normal range. In addition, a scintigraphy or an echography of the thyroid gland may subsequently occur.

Treatment of hypothyroidism consists of giving thyroxine hormones as medication known as levothyroxine. Usually this medication has to be taken daily and for the rest of one’s life. The dose of levothyroxine depends on the age, weight and the patient’s profile. Doctors will start with a prescribed dose and check the efficiency after four to six weeks. The dose can be adjusted until the TSH is in normal range, thus regular checking of the thyroid in the blood is vital for proper follow ups. 

A rare form of hypothyroidism is congenital hypothyroidism (CHT) in newborns. This condition occurs due to an underdevelopment of the thyroid in the baby resulting in insufficient to no production of thyroid hormones. Thyroid hormones are essential for the normal development of the brain and normal growth of children. These babies can look normal at birth and vague symptoms can develop later on, such as jaundice, poor growth, constipation and floppiness. If untreated, it can also lead to mental retardation. In most countries, newborns receive a heel-prick blood test where this can properly be screened and treated if necessary. 

Hyperthyroidism is usually caused by Graves’ disease and is the most common cause of hyperthyroidism in the UK. In Graves’ disease, there is a production of antibodies against the TSH receptor of the thyroid and leading to overstimulation of this gland. Graves’ disease is common in women between the ages of 30-50. 

Other uncommon causes of hyperthyroidism are infections of the thyroid (thyroiditis), medication (amiodarone) and toxic nodular goitre. These patients present themselves with symptoms of weight loss, excessive sweating, increased appetite, tiredness, fast heartbeat, trembling (tremor), hair loss, diarrhea and if left untreated it can lead to heart failure. 

In women, hyperthyroidism can also lead to infertility and menstruation disorders such as heavy, frequent menstruations or even absent menstruations. Sometimes these symptoms are not properly recognised and can go undiagnosed for several years. Thus, it is important to evaluate the thyroid function in non-specific symptoms. 

In elderly patients, other symptoms such as dementia and depression can also occur. In Graves’ disease, there are also eye symptoms such as bulging eyes with eye discomfort and double vision. 

The diagnosis of hyperthyroidism is made on the clinical symptoms accompanied with a blood test like that stated above for hypothyroidism. for checking the TSH, T4, T3, TSH-R antibodies (Graves’ disease).

Treatment of hyperthyroidism relies in suppressing the excessive production of the thyroid hormones. This can be done by medication, known as the thio-ureum derivaten (carbimazole, strumazole, PTU). They inhibit the synthesis of the thyroid hormones and they can be given either on a short-term (just prior to surgery) or on a long-term basis. 

However, such medications can cause serious side effects which can lead to severe infections and hepatitis, thus it is not preferable to continue on them on a long term basis. While waiting for another proper treatment, symptoms of hyperthyroidism can be temporary suppressed with b-blockers.

The second step is radioactive iodine (iodine-131) treatment. With this medication, the thyroid gets destroyed while the effect becomes clear after 3-4 months. Sometimes this can lead to an underactive thyroid. 

Surgical removal of the thyroid gland is used as a last resort in the treatment of hyperthyroidism. This either includes a partially removed thyroid gland or a total removal of the gland. Surgery of the thyroid is indicated when the treatment above with medications fails. 

A regular check-up of the thyroid hormones remains important and is vital for a proper follow up. 

(Please always consult a doctor or specialist to diagnose health conditions and follow the advised plan of a qualified doctor)

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