Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone. It is the most common thyroid disorder.

The thyroid is a butterfly-shaped gland in the middle of the neck, located below the larynx (voice box) and above the clavicles (collarbones). The thyroid produces two hormones, triiodothyronine (T3) and thyroxine (T4), which regulates how the body uses and stores energy (also known as the body’s metabolism). Thyroid function is controlled by a gland in the brain, known as the pituitary. The pituitary produces the thyroid-stimulating hormone (TSH), which stimulates the thyroid to produce T3 and T4.

CAUSES OF HYPOTHYROIDISM

In about 95% of cases, hypothyroidism is due to a problem in the thyroid gland itself and is called primary hypothyroidism. However, certain medications and diseases can also decrease thyroid function. In some cases, hypothyroidism is a result of decreased production of the thyroidstimulating hormone (TSH) by the pituitary gland (called secondary hypothyroidism).

Hypothyroidism commonly develops in adult women and becomes more common with increasing age. Thyroid problems generally occur more commonly in Caucasian than in Black populations. However, it can occur at any age and can affect anyone.

The most common cause of primary hypothyroidism is due to an autoimmune disease called autoimmune thyroiditis(Hashimoto’s thyroiditis). The immune system normally makes antibodies to attack bacteria, viruses, and other germs. If you have an autoimmune disease, the immune system makes antibodies against certain tissues of your body.

With autoimmune thyroiditis, you make antibodies that attach to your own thyroid gland, which affect the gland’s function. The thyroid gland is then not able to make enough thyroxine and hypothyroidism gradually develops. It is thought that something triggers the immune system to make antibodies against the thyroid but the trigger is not known. Some people with autoimmune thyroiditis also develop a swollen thyroid gland(goitre).

Autoimmune thyroiditis is more common in patients with:

• A family history of hypothyroidism caused by autoimmune thyroiditis.
• Down’s syndrome. Hypothyroidism develops in 1 in 3 people with Down’s syndrome before the age of 25 years. Symptoms of hypothyroidism may be missed more easily in people with Down’s syndrome, therefore,
  some doctors recommend that all people with Down’s syndrome should have an annual blood test to screen for hypothyroidism.
• Turner syndrome. An annual blood test to screen for hypothyroidism is usually advised for people with this condition.
• An enlarged thyroid gland (diffuse goitre).
• A past history of Graves’ disease or thyroiditis following childbirth.
• A personal or family history of other autoimmune disorders – for example: Vitiligo, Pernicious Anaemia, Addison’s Disease, type 1 Diabetes, Premature Ovarian Failure, Coeliac Disease, Sjögren’s Syndrome.

Other causes of hypothyroidism include:

• Worldwide, iodine deficiency is a common cause of hypothyroidism. (Your body needs iodine to make thyroxine.) This affects some countries more commonly than others, depending on the level of iodine in the diet.
• A side-effect to some medicines – for example, amiodarone and lithium.
• Inflammation of the thyroid (thyroiditis).
• A pituitary gland problem is a rare cause (secondary hypothyroidism).
• Some children are born with an underactive thyroid gland (congenital hypothyroidism).

SYMPTOMS OF HYPOTHYROIDISM

The symptoms of hypothyroidism vary widely – some people have no symptoms, while others have dramatic symptoms. These symptoms are notorious for being nonspecific and for mimicking many of the normal changes of aging. Usually, symptoms are milder when hypothyroidism develops gradually.

General symptoms – The thyroid hormone normally stimulates the metabolism and most of the symptoms of hypothyroidism reflect slowing of metabolic processes. General symptoms may include fatigue, sluggishness, weight gain and intolerance of cold temperatures.

Skin – Hypothyroidism can decrease sweating. The skin may become dry and thick. The hair may become coarse or thin, eyebrows may disappear and nails may become brittle.

Eyes – Hypothyroidism can lead to mild swelling around the eyes. People who develop hypothyroidism after treatment for Graves’ disease may retain some of the eye symptoms of Graves’ disease, including protrusion of the eyes, the appearance of staring and impaired movement of the eyes.

Cardiovascular System – Hypothyroidism slows the heart rate and weakens the heart’s contractions, decreasing its overall function. Related symptoms may include fatigue and shortness of breath with exercise. These symptoms may be more severe in people who also have heart disease. In addition, hypothyroidism can cause mild high blood pressure and can raise blood levels of cholesterol.

Respiratory System – Hypothyroidism weakens the respiratory muscles and decreases lung function. Symptoms can include fatigue, shortness of breath with exercise and decreased ability to exercise. Hypothyroidism can also lead to swelling of the tongue, hoarse voice and sleep apnea. Sleep apnea is a condition in which there is intermittent blockage of the airway while sleeping, causing irregular sleep patterns and daytime sleepiness.

Reproductive System – Women with hypothyroidism often have menstrual cycle irregularities, ranging from absent or infrequent periods to very frequent and heavy periods. The menstrual irregularities can make it difficult to become pregnant; and pregnant women with hypothyroidism have an increased risk for miscarriage during early pregnancy. Treatment of hypothyroidism can decrease these risks.

Myxoedema Coma – In people with severe hypothyroidism, trauma, infection, exposure to the cold and certain medications can rarely trigger a life-threatening condition called myxoedema coma, which causes a loss of consciousness and hypothermia (low body temperature).

DIAGNOSIS OF HYPOTHYROIDISM

Blood tests can confirm the diagnosis and pinpoint the underlying cause of the thyroid hormone deficiency. The most common blood test for hypothyroidism is TSH (thyroid stimulating hormone). TSH is the most sensitive test because it can be elevated even with small decreases in thyroid function. Thyroxine (T4), the main product of the thyroid gland, may also be measured to confirm and assess the degree of hypothyroidism.

HYPOTHYROIDISM WITHOUT SYMPTOMS

In some cases, hypothyroidism is extremely mild or causes no obvious symptoms (called subclinical hypothyroidism). The decision to treat subclinical hypothyroidism with T4 is controversial and is dependent on many patient factors. Your doctor will be able to advise you on treatment options.

SURGERY

Hypothyroidism can increase the risk of certain surgery-related complications; bowel function may be slow to recover and infection may be overlooked if there is no fever. If preoperative blood tests reveal low thyroid hormone levels, non-emergency surgery is usually postponed until treatment has returned T4 levels to normal.

TREATMENT OF HYPOTHYROIDISM

The goal of treatment for hypothyroidism is to return blood levels of TSH and T4 to the normal range and to alleviate symptoms. The treatment for hypothyroidism is thyroid hormone replacement therapy. This is usually given as an oral form of T4. Generic(levothyroxine) and brand-name (Euthyrox®, Eltroxin®, Synthroid®) formulations are equally effective. However, it is preferable to stay on the same type of T4 rather than switching between brand name and/or generic formulations. If a switch is necessary, a blood test is usually done six weeks later to determine if the dose needs to be adjusted.

If you have untreated hypothyroidism:

• You have an increased risk of developing heart disease. This is because a low thyroxine level causes the blood lipids (cholesterol, etc) to rise.
• If you are pregnant, you have an increased risk of developing some pregnancy complications (eg. pre-eclampsia, anaemia, premature labour, low birth weight, stillbirth and serious bleeding after the birth).
• Women often need higher doses of T4 during pregnancy. Testing is usually recommended every four weeks, beginning after conception. Once the optimal T4 dose is established, testing is usually repeated at least once per trimester. After delivery, the woman’s dose of T4 will need to be adjusted again.
• Hypothyroid coma (myxoedema coma) is a very rare complication.

IN CONCLUSION

Hypothyroidism is a common disorder. Symptoms develop gradually and may be confused with other conditions. The diagnosis of hypothyroidism can be easily made with a blood test. Treatment with levothyroxine is easy, cheap and effective.

SYMPTOMS OF HYPERTHYROIDISM INCLUDE:

• Being restless, nervous, emotional, irritable, sleeping poorly and ‘always on the go’.
• Tremor of your hands.
• Warm, moist hands.
• Weight loss, despite an increased appetite.
• Palpitations (sensation of your heart beating fast).
• Rapid pulse.
• Sweating.
• Heat intolerance / preference for cooler weather.
• Increased thirst.
• Diarrhoea or needing to go to the toilet more often than normal.
• Shortness of breath.
• Skin problems such as hair thinning and itchiness.
• Menstrual changes (in women) – your periods may become very light or infrequent.
• Fatigue.
• Muscle weakness (difficulty climbing stairs, standing from a seated position or combing your hair).
• Swelling of your thyroid gland (a goitre).
• Eye problems (bulging, redness, itchiness or dryness of your eyes) if you have Graves’ disease.

Most people with hyperthyroidism do not have all the symptoms but a combination of two or more is common. Symptoms usually develop slowly over several weeks. All the symptoms can be caused by other problems and so the diagnosis may not be obvious at first. Symptoms may be mild to start with but become worse as the level of thyroxine in the blood gradually rises.

CAUSES OF HYPERTHYROIDISM
Graves’ disease
This is the most common cause of hyperthyroidism. It is not clear why Graves’ disease develops in most people, although it is more common in certain families. There may also be family members with other autoimmune diseases (eg. diabetes, rheumatoid arthritis and myasthenia gravis).

Graves’ disease is an autoimmune condition. The immune system normally makes antibodies (tiny proteins that travel in the bloodstream) to attack bacteria, viruses and other germs. In autoimmune diseases, the immune system makes antibodies against tissues of the body. In Graves’ disease the body’s immune system turns against the thyroid gland and produces an antibody that stimulates the thyroid gland to produce too much thyroid hormone. Autoimmune thyroid disease has a strong genetic component. It is thought that something triggers the immune system to make these antibodies. The trigger is not known. Stress also seems to play a role and sometimes people with Graves’ disease may have experienced major stresses in their lives a year or so before Graves’ disease is diagnosed.

Graves’ disease is most common in women between the ages of 20 and 40 years, but can occur at any age in men or women. The thyroid gland enlarges (called a goitre) and makes excessive amounts of thyroid hormone, causing symptoms of hyperthyroidism.

Some people develop eye problems (called Graves’ ophthalmopathy or orbitopathy), which causes dry, irritated or red eyes, and in severe cases may cause double vision. Others develop swelling behind or around the eyes that causes the eyes to bulge out, or inflammation of muscle in the eyelids that can cause excessive lid opening. The more severe manifestations of Graves’ eye disease are uncommon, except in smokers.

Thyroid Nodules
This is a less common cause of hyperthyroidism and is characterised by one or more nodules or lumps in the thyroid that may gradually grow and increase their activity so that the total output of thyroid hormone into the blood is greater than normal. This condition is known as toxic nodular or multinodular goitre.

Thyroiditis
Painless (“silent or lymphocytic”) thyroiditis and postpartum thyroiditis are disorders in which the thyroid becomes temporarily inflamed and releases thyroid hormone into the bloodstream, causing hyperthyroidism. Postpartum thyroiditis can occur several months after delivery. The hyperthyroid symptoms may last for several months, often followed by several months of hypothyroid symptoms, such as fatigue, muscle cramps, bloating, and weight gain. Subacute (granulomatous) thyroiditis is thought to be caused by a virus. It causes a painful, tender, enlarged thyroid gland. The thyroid becomes inflamed and releases thyroid hormone into the blood stream; the hyperthyroidism resolves when the viral infection improves, and may also be followed by several months of hypothyroid symptoms.

Other causes
Taking too much thyroid hormone medication for hypothyroidism. Some people who take the medicines amiodarone and lithium may develop hyperthyroidism. There are various other rare conditions that result in excess thyroxine being made.

TREATMENT OF HYPERTHYROIDISM

The main aim of treatment is to reduce your level of thyroxine to normal. Other problems, such as a large goitre (thyroid swelling) or associated eye problems, may also need treatment. Factors such as the underlying cause of the problem, your age and the size of any goitre are taken into account to decide on the best treatment plan.

Treatment options include the following:
Medicines (carbimazole / neomercazole) Carbimazole reduces the formation of thyroxine by an overactive thyroid gland. It may take 4 to 8 weeks of treatment for your thyroxine level to come down to normal. The dose of carbimazole needed to keep the thyroxine level normal varies from person to person. A high dose is usually given initially which is then reduced as your thyroxine levels come down.

Carbimazole can, rarely, affect your white blood cells which fight infection. If you develop a fever, sore throat, mouth ulcers or other symptoms of infection whilst taking carbimazole, you should stop taking it and see a doctor urgently for a blood test.

RADIOIODINE

This involves taking a drink, or swallowing a capsule, which contains radioactive iodine. The main use of iodine in the body is to make thyroxine. Therefore, the radioactive iodine builds up in the thyroid gland. As the radioactivity is concentrated in the thyroid gland, it destroys some thyroid tissue which reduces the amount of thyroxine that you make.

The dose of radioactivity to the rest of the body is very low and is not dangerous. However, it is not suitable if you are pregnant or breast-feeding. In addition, after treatment, women should not become pregnant for at least six months and men are advised not to father children for at least four months. Your specialist will give detailed advice regarding this form of therapy.

TREATMENT FOR EYE PROBLEMS

You may need to see an eye specialist if you develop the eye problems of Graves’ disease. Relatively minor symptoms affect the eyes in about half of people with Graves’ disease. Measures such as artificial tears, sunglasses and eye protectors whilst you sleep may be sufficient to help.

Regular checks are recommended, even after you finish a successful treatment. It is very important to have regular blood tests to check that you have the right level of thyroid hormone (thyroxine) in your blood. This is because some people become hyperthyroid again at some time in the future.

Others who have been treated successfully develop an underactive thyroid in the future. If this occurs, it can usually be treated easily with thyroxine tablets.

SURGERY
This involves removing part of your thyroid gland. It may be a good option if you have a large thyroid swelling (goitre) which is causing problems in your neck. If too much thyroid tissue is removed then you will be given thyroxine tablets to keep your thyroxine level normal. It is usually a safe operation but, as with all operations, there is a small risk.

TO SUMMARISE

Hyperthyroidism is a condition where the thyroid produces more thyroxine than is needed by the body. Symptoms vary greatly amongst individuals and a diagnosis can be established with a blood test. Hyperthyroidism can be successfully treated with medication, radioactive iodine therapy or surgery.