Hyperthyroidism (or overactivity of the thyroid gland) is a condition in which the thyroid gland makes too many thyroid hormones: triiodothyronine (T3) and thyroxine (T4).
Hormone levels of T3 and T4 in the blood are affected by TSH (thyrotropin), a hormone produced in the pituitary gland (or pituitary gland).
The normal values (reference values) of these hormones are:
- TSH: between 0.3 and 5.5 mIU/l
- Total triiodothyronine (T3) 80 – 220 ng/dl
- Free triiodothyronine (FT3) in adults 260-480 pg/dl
- Free thyroxine (FT4) 0.7 – 1.8 ng/dl
- Total thyroxine (T4) 4 – 12.3 μg/dl
Hyperthyroidism can noticeably increase the metabolism in the body and thus cause some symptoms, such as sudden weight loss, fast or irregular heartbeat, sweating, nervousness or irritability.
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What is the thyroid gland?
The thyroid gland is a gland with the shape of a butterfly. It is 5 cm long and weighs less than 30 grams.
It is located at the front of the neck under the larynx and has two lobes, one laterally next to the trachea.
The thyroid gland is a gland that belongs to the endocrine system. The glands of the endocrine system generate, store and release hormones into the bloodstream.
The hormones are distributed throughout the body and control the activity of the body’s cells.
The thyroid gland produces two thyroid hormones, triiodothyronine (T3) and thyroxine (T4).
The T3 comes from the T4 and is the more active form because it directly affects the tissue.
The thyroid hormones affect metabolism, brain development, breathing, heart, nervous system, body temperature, muscle strength, skin dryness, menstrual cycle, body weight and cholesterol levels.
The production of the thyroid hormones T3 and T4 is controlled by the hormone TSH, which is produced in the pituitary gland. If thyroid hormone levels in the blood are lowered, the pituitary gland releases more TSH. If the thyroid hormones are elevated, the pituitary gland responds with reduced TSH production.
Classification of hyperthyroidism
- One speaks of primary hyperthyroidism when the disease arises in the thyroid gland.
- Secondary hyperthyroidism means that the thyroid gland is caused by an excess of thyrotropin (TSH) in the bloodstream.
Hyperthyroidism is:
- evident when it is fully developed and the symptoms are typical of the disease;
- subclinical, if symptoms are mild or nonspecific and do not indicate thyroid dysfunction.
Risk factors of hyperthyroidism
Hyperthyroidism, especially Graves’ disease, is hereditary and occurs more frequently in women than in men.
If another family member has thyroid disease, you should talk to your doctor to find out what it can mean for health and if they have a recommendation on how to keep thyroid function under control.
What are the causes of hyperthyroidism?
Hyperthyroidism has several causes, including:
- Graves’ disease
- Thyroid nodules
- Thyroiditis or thyroid inflammation
- Intake of too much iodine
- Taking too many synthetic thyroid hormones commonly used to treat hypothyroidism, such as medications such as Euthyrox
Rarely, hyperthyroidism is caused by pituitary adenoma, a noncancerous tumor of the pituitary gland. In this case, hyperthyroidism arises from too much TSH.
Graves’ disease
Graves’ disease is also known as toxic diffuse goiter (goiter) and is the most common cause of hyperthyroidism in adults, adolescents and children.
Graves’ disease is an autoimmune disease.
Normally, the immune system protects the body from infection by identifying and destroying bacteria, viruses, and other harmful foreign substances.
But in autoimmune diseases, the immune system attacks the cells of the body and organs.
In Graves’ disease, the immune system produces autoantibodies called thyroid stimulating immunoglobulins (TSI), which attach to the outer membrane of thyroid cells. The TSI acts like the TSH and stimulates the thyroid gland to produce thyroid hormone.
Thyroid nodules
Thyroid nodules, also called adenomas, are masses of tissue that form in the thyroid gland.
Thyroid nodules are common and are usually non-tumorous. They occur in about 5% of the population of the United States.
These nodules can become overactive and produce too much thyroid hormone.
A single hyperactive node is called toxic adenoma. Many hyperactive nodules are called multinodular toxic goiter.
Malignant thyroid nodules can lead to changes in the voice and enlarged lymph nodes,
and in the more serious cases they cause swallowing disorders.
Thyroiditis
Thyroiditis is an inflammation of the thyroid gland that leads to the release of thyroid hormones from the thyroid gland. First of all, the release leads to high levels of hormones in the blood, which cause hyperthyroidism for 1-2 months.
Most people then develop hypothyroidism, which means that thyroid hormone levels become too low before the thyroid gland is completely healed.
Several types of thyroiditis can cause hyperthyroidism, followed by hypothyroidism:
- Subacute thyroiditis. This disease provokes painful inflammation and enlargement of the thyroid gland.
Experts are not sure about the cause of subacute thyroiditis, it may be associated with a viral or bacterial infection. The disease usually passes on its own after a few months. - Postpartum thyroiditis. This type of thyroiditis develops in a woman after childbirth.
- Silent thyroiditis. This thyroiditis is called “silent” because it is painless like postpartum thyroiditis, even though the thyroid gland may be enlarged. Like postpartum thyroiditis, silent disease is thought to be an autoimmune disease and sometimes develops the state of permanent hypothyroidism.
Too much iodine in the diet
The thyroid gland needs iodine for the production of hormones, so the amount of iodine consumed affects the amount of thyroid hormones.
Some individuals who consume a large amount of iodine may have an excess secretion of thyroid hormone.
Some medications contain significant amounts of iodine, such as amiodarone, which is used to treat heart disease, or supplements containing algae.
Some cough syrups contain a large amount of iodine.
Which table salt should you eat? Recommended is table salt with low iodine content, in any case it is better to reduce this food in the diet as much as possible.
Many people think that you should not go to the sea if you suffer from hyperthyroidism because you can inhale iodine. In fact, however, it is only important to consume little iodine with food.
Too many drugs with synthetic thyroid hormones
Some people who take synthetic thyroid hormones as a treatment for hypothyroidism may overdo it. People taking such hormones should consult the doctor at least once a year to control thyroid hormone levels and follow the doctor’s dose recommendations.
Some other medications can interact with synthetic thyroid hormones and raise hormone levels in the blood.
Anyone taking synthetic thyroid hormones should ask the doctor about possible interactions when they start taking new medications.
What are the symptoms of hyperthyroidism?
- Restless, nervous, emotional, irritable and capricious behavior
- Stress and anxiety
- Constant urge to move
- Insomnia
- Hand trembling
- Weight loss despite increased appetite
- Palpitations
- Sweating, heat aversion and increased thirst. Some patients do not freeze in winter and can walk around short-sleeved even at 10° outside temperature.
- Diarrhea or more frequent bowel movements than usual
- Problems such as hair loss or itching
- Fragile nails
- Changes in the menstrual cycle – menstruation can become very weak or less frequent, in some cases it can even stop altogether (amenorrhea), even if the woman is not yet in menopause.
- Fatigue and muscle weakness are often complained of by patients
- Difficulty concentrating
- Amnesia
- There may be swelling of the thyroid gland (a goiter) on the neck
- Visual disturbances in Graves’ disease
- Protruding eyes
- Reduction of female and male fertility and reduction of libido (sexual desire)
- Hyperthyroidism can lead to weight loss because the metabolism is accelerated.
- The thyroid hormones can increase blood sugar because glycolysis is favored, which increases the risk of diabetes.
- Hypercalcemia (increase in calcium levels in the blood)
Most people with hyperthyroidism do not suffer from all symptoms, but a combination of at least two of them is common.
Symptoms develop slowly, usually over a few weeks, when hyperthyroidism is moderate or severe.
All symptoms can also be caused by other diseases, so the diagnosis may not be clear at first.
Symptoms may be mild at the first stage, but they worsen as the level of thyroxine in the blood gradually increases.
Possible complications or consequences of hyperthyroidism
Untreated hyperthyroidism can lead to the following consequences:
- A higher risk of heart disease such as arrhythmia, atrial fibrillation, weak heart (cardiomyopathy), angina pectoris or heart failure.
- Pregnant women have a higher risk of developing a complication during pregnancy.
- There is an increased risk of brittle bones (osteoporosis).
- Under treatment, the outlook is good. With successful treatment, most symptoms, risks and complications pass.
Hyperthyroidism in pregnancy
During pregnancy, hyperthyroidism is usually caused by Graves’ disease and occurs in women in one in 500 pregnancies.
Uncontrolled hyperthyroidism increases the possibility of miscarriage, premature labor and preeclampsia, that is, a dangerous increase in blood pressure in late pregnancy.
Hyperthyroidism can have consequences in a newborn:
- acceleration of heart rate (tachycardia), which can lead to heart failure;
- premature closure of the cranial sutures (joints between the bones of the skull);
- insufficient weight gain;
- Irritability;
- sometimes an enlargement of the thyroid gland can press on the trachea and interfere with breathing.
Women with Graves’ disease and their newborns require medical attention.
Women with hyperthyroidism should talk about their condition with their doctor before they become pregnant.
The symptoms of hyperthyroidism can be difficult to assess during pregnancy.
Normally, the thyroid gland becomes larger in healthy women who become pregnant.
Some signs of hyperthyroidism include:
- fast and irregular heartbeat,
- slight tremors,
- unexplained weight loss,
- no normal weight gain.
Postpartum thyroiditis
This thyroid infection affects about 5-10 percent of women in the first year after giving birth.
Postpartum thyroiditis leads to hyperthyroidism, which generally lasts 1 to 2 months and is believed to be an autoimmune disease.
This disease is probably repeated in further pregnancies.
Postpartum thyroiditis is sometimes undiagnosed because the symptoms are confused with those of postpartum depression, such as fatigue and mood swings that sometimes occur after the birth of a child.
If the signs of fatigue do not go away within a few months or a woman develops postpartum depression, she should talk to her doctor about it.
The woman may have developed permanent thyroid disease and need medication.
