What is an overactive thyroid gland and what are its causes?

An overactive thyroid gland is a disorder in which the thyroid gland produces too much hormone for the body’s needs. The thyroid gland is a small organ located at the base of the neck. It is responsible for the production and release of two hormones: triiodothyronine (T3) and thyroxine (T4), which regulate the function of most body tissues, influence the metabolism of our body and thermogenesis (heat production). The thyroid gland is controlled by the pituitary gland, which releases thyroid stimulating hormone (TSH), which stimulates the thyroid gland to produce the hormones T3 and T4.

The activity of the thyroid and pituitary gland is closely related (referred to as negative feedback), in which the increased concentration of thyroid hormones reduces the release of TSH by the pituitary gland, and the deficiency of these hormones increases the production of TSH, which in turn stimulates the thyroid to produce more T3 and T4.

Dig. 1.The thyroid gland is a small organ located at the base of the neck
The most common causes of hyperthyroidism in Poland include:

• Graves’ disease (an autoimmune disease in which your own antibodies stimulate the thyroid gland to produce hormones )
• thyroid nodules(hyperactive [toxic] nodular goiter, thyroid autonomic tumor).

The less common causes of hyperthyroidism include:subacute thyroiditis(a disease associated with a previous viral infection) and postpartum thyroiditis.

How common is hyperthyroidism?

Hyperthyroidism is one of the most common endocrine diseases; it affects about 1-2% of adults in Poland. It affects mainly women aged 20–40, but it rarely occurs in children.

How is hyperthyroidism manifested?

The thyroid cell does not produce and does not release hormones if it is not stimulated by TSH.

Under the influence of TSH, both hormone secretion and growth processes are activated.

Antibody against the TSH receptor activates the synthesis and secretion of thyroid hormones, and in some cases it also activates other intracellular processes dependent on TSH , including growth. Some antibodies bind to the receptor but do not activate it, but they block TSH, which causes

hypothyroidism. Mutations that activate the TSH receptor lead to the formation of a receptor protein that constantly transmits a signal. Then the thyroid gland secretes thyroid hormones even without TSH (autonomously).

G– G protein,

AC– adenylate cyclase

The main symptoms that suggest an overactive thyroid gland are:

• feeling hot
• increased sweating
• nervousness, anxiety, irritability
• shaking hands
• losing weight, despite increased appetite
• more frequent bowel movements /diarrhea
• increased heart rate, feelingyour heart racing
• muscle weakness
• hair loss
• eye symptoms – exophthalmos, double vision,swellingand redness of the eyelids or conjunctiva (typical for Graves’ disease)
• menstrual disorders,infertility.

The extent of symptoms may vary from patient to patient. In the elderly, the symptoms of hyperthyroidism may be less pronounced. Weakness and problems with the circulatory system may predominate – heart rhythm disturbances (atrial fibrillation), symptomsof heart failure.

What to do in the event of symptoms?

A person who finds symptoms suggesting the presence of hyperthyroidism should see a family doctor who, after a medical examination (after taking an anamnesis and after the examination), will decide on the need to measure the serum TSH level. The test is performed with a blood sample that does not have to be taken on an empty stomach. In the case of very severe hyperthyroidism, it is necessary to urgently refer the patient to a hospital.

How does the doctor make a diagnosis?

In order to confirm an overactive thyroid gland, it is necessary to undergo hormonal tests. An initial test to assess thyroid function (blood TSH levels) may be ordered by your GP. If the result is incorrect, it is necessary to measure the concentration of free thyroid hormones (FT4 and / or FT3). Hyperthyroidism is diagnosed if a decreased TSH concentration is accompanied by an increased FT4 and / or FT3 concentration in the serum.

If an overactive thyroid is diagnosed, the doctor will try to determine its cause, which is important when deciding on the treatment method. The following studies are helpful for this:

• Thyroid ultrasound: in the case of nodular goiter, the presence of focal lesions in the thyroid gland can be detected; while in the case of Graves’ disease, the echogenicity is reduced
• serum anti-thyroid antibodies, especially anti-TSH receptor antibodies (anti-TSHR): elevated levels of anti-TSHR are characteristic of Graves’ disease
• fine-needle aspiration biopsy (FNAB) of the thyroid gland – performed if there are focal changes in the thyroid gland (see thyroid nodules)
• thyroid scintigraphy performed in selected situations.

What are the treatments?

There are many ways to treat an overactive thyroid gland. There is no single best treatment as each method has advantages and disadvantages that can be discussed with your healthcare professional. In addition, the treatment of hyperthyroidism depends on its cause, degree of severity, age of the patient, and comorbidities. Hence, the best method of treatment is determined individually for each patient. Most often it begins with the use of drugs that reduce the production of thyroid hormones, usually also when treatment is planned by another method (surgery or radioiodine¹³¹I).

Hyperthyroidism should not be taken lightly, and if left untreated, it can lead to dangerous complications, e.g. cardiac arrhythmias, heart failure,osteoporosisor thyroid crisis (with a life-threatening increase in T3 and T4 levels). In pregnant women, hyperthyroidism is detrimental to both the mother and the fetus (seeHyperthyroidism in pregnancy). Treatment of hyperthyroidism requires compliance with medical recommendations, regular medication and regular medical check-ups.

In the treatment of hyperthyroidism, the following are used:

• drug treatment with antithyroid drugs (thyreostatic drugs).Antithyroid drugs includethiamazoleandpropylthiouracil. Thyreostatics inhibit the production of hormones in the thyroid gland and their effect becomes apparent after about 2–4 weeks of use. Each time the doctor determines the starting dose of the drug individually. Adjunctive therapy with ß-blockers, e.g.propranolol , is also frequently usedwhich do not lower thyroid hormone levels by themselves, but help to control some symptoms, such as trembling hands and the feeling of a fast heartbeat. During the treatment, the doctor controls the effectiveness of the therapy through clinical evaluation (interview and examination of the patient) and determination of the concentration of thyroid hormones, and adjusts the dose accordingly. Undesirable effects may occur during treatment with thyreostatic drugs.
  In the event of any disturbing symptom that may be related to the commencement of treatment, the patient should report it to the doctor as soon as possible. For minor complications (e.g.itchyskin,joint pain) it is enough to change the drug or its dose. In some, very rare cases, it may be necessary to discontinue thyreostatic treatment.
  A particularly dangerous, but fortunately extremely rare complication can be agranulocytosis, a significant decrease in the amount of neutrophils (a type of white blood cell) in the serum due to reversible toxic bone marrow damage that resolves after drug discontinuation, but requires close medical supervision. This is a very dangerous condition because the body’s resistance to infection is greatly impaired. That is why in the event offever, weakness,sore throatthe patient should stop taking the drug immediately and go to the clinic or hospital urgently for morphology control with a smear. If the neutrophil count is not decreased, early treatment should be initiated promptly. If agranulocytosis is confirmed, this group of drugs must never be used again in the future.
• radioiodine treatment (¹³¹I).Single oral administration of radioiodine is designed to slow, irreversible damage to the thyroid cells that actively take up iodine from the blood. The radioiodine effect develops within a few months after therapy. The development of permanent hypothyroidism (requiring treatment with thyroxine tablets) cannot be regarded as a complication, but as an effect of effective treatment. This form of therapy must not be used in pregnant women and during breastfeeding. Additionally, for a period of about a week, the treated person should not have contact with young children and pregnant women. Finally, women should not plan a pregnancy for at least 6 months after treatment.
• surgical treatment (strumectomy, thyroidectomy).This form of therapy is absolutely indicated in the case of suspected or diagnosedthyroid cancer, including coexisting with hyperthyroidism (see:Thyroid nodules). Moreover, surgical treatment is considered in patients with high goiter compressing the trachea. After surgery to remove the thyroid gland, hypothyroidism occurs, which requires constant treatment with thyroxine preparations. Unfortunately, during the operation, you must take into account the possibility of complications that should be discussed with the consulting surgeon. Severe postoperative complications include: paresis / paralysis of one or both vocal cords as a result of perioperative damage to the retrograde laryngeal nerves, and transient or permanent hypoparathyroidism.

Is it possible to recover completely?

The possibility of a complete recovery (the patient does not require any thyroid medication) depends mainly on the cause of the hyperthyroidism . Hypothyroidism is common after radioiodine treatment or after thyroidectomy, requiring continued treatment with thyroxine preparations for the rest of your life (seeHypothyroidism).

What should I do after treatment is finished?

After the treatment of hyperthyroidism has been completed, the patient requires further constant medical care. Periodic hormonal control (serum TSH concentration) and ultrasound (ultrasound of the thyroid gland) are recommended. In some cases, there is a possibility of relapse of hyperthyroidism, recurrence of nodular goiter or development of hypothyroidism after the treatment, even many months after its completion. If the patient, after completing the therapy, requires treatment with oral thyroid hormone preparations due to hypothyroidism, it is necessary to take them regularly and periodically check the effectiveness of this treatment.

What to do to avoid getting sick?

As part of a healthy lifestyle, you should take care of taking the right amount of iodine in your diet. In Poland, iodization of table salt is obligatory, which means that most people take the right amount of iodine. Moreover, according to preventive programs, apart from the obligatory iodization of table salt, it is recommended to eat foods rich in iodine (including sea fish) and to take iodine in the form of oral preparations by pregnant and breastfeeding women. Adequate iodine supply reduces the risk of developing parenchymal goiter and thyroid nodules, and thus also of hyperthyroidism in the course of thyroid nodules.

The second important factor that can be modified is smoking cessation. There is a connection between smoking and the development of thyroid nodules as well as the development and course of hyperthyroidism.

Autoimmune thyroid diseases (e.g. Graves’ disease,Hashimoto’s disease) are genetically determined diseases. We have no influence on the genetic predisposition of people with burden. People with a family history of autoimmune thyroid disease should inform their physicians in order to avoid certain medications that may affect the development of the disease.