Overview: What is hypothyroidism?
In hypothyroidism, insufficient amounts of the iodine-containing thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) are produced and released. The body needs these hormones to regulate metabolism. In the case of a deficiency of T3 and T4, many metabolic processes therefore only run at a reduced rate. This can result in a wide variety of complaints.
Hypothyroidism – frequency and age
Hypothyroidism is one of the most common hormone-related diseases. About one in 3,000 to 4,000 children is born with hypothyroidism (congenital hypothyroidism). In the majority of cases, however, hypothyroidism develops in the course of life (acquired hypothyroidism). With increasing age, the frequency of the disease increases. Women are affected more frequently than men.
Hypothyroidism: causes and risk factors
Depending on where the reason for the thyroid’s lack of hormone production lies, a distinction is made between primary, secondary and tertiary hypothyroidism:
Primary hypothyroidism
The reason for this by far the most common form of hypothyroidism is found in the thyroid gland itself – functioning thyroid tissue is damaged or destroyed for a variety of reasons. In most cases, the reason is Hashimoto’s thyroiditis. This is a chronic inflammation of the thyroid gland based on an autoimmune reaction, i.e. a misregulation of the immune system: the body’s defense system attacks thyroid tissue. This entails a prolonged inflammation, in the course of which the tissue is gradually destroyed. Thus, the thyroid gland can produce less and less hormones – hypothyroidism develops.
Other possible causes of primary hypothyroidism include.
- inflammation of the thyroid gland caused by other factors (viral, drug-induced in certain cancer therapies)
- chronic iodine deficiency
- Surgical removal of the thyroid gland (completely or partially), for example in cases of hyperthyroidism or thyroid cancer
- Radioiodine therapy (taking radioactive iodine to treat hyperthyroidism or thyroid cancer).
- certain medications, for example thyrostatic drugs (for hyperthyroidism), amiodarone (for cardiac arrhythmias), lithium (for mental disorders)
- Radiation therapy to the head or neck, usually for cancer (such as thyroid or laryngeal cancer).
- Hereditary diseases that affect the production or secretion of thyroid hormones (congenital hypothyroidism)
Secondary hypothyroidism
This rare form of hypothyroidism is caused by a disorder in the pituitary gland. This brain region stimulates hormone production in the thyroid gland via its own hormone (TSH = thyroid-stimulating hormone). However, this signal is absent if the pituitary gland secretes too little TSH due to a disease (for example, a tumor).
Tertiary hypothyroidism
Tertiary hypothyroidism is due to a dysfunction of the hypothalamus – another brain region involved in the complex regulatory circuit between the brain and the thyroid gland. The hypothalamus produces the hormone TRH (Thyrotropin Releasing Hormone). It stimulates the pituitary gland to release TSH, which in turn stimulates thyroid hormone production. This means that if the hypothalamus releases too little TRH, for example due to a tumor or inflammation, the production of thyroid hormones is ultimately also reduced. However, such tertiary hypothyroidism is rare.
Symptoms: hypothyroidism
The symptoms of hypothyroidism are very diverse and can vary from individual to individual. The severity of the disease plays a role, as does the age of the person affected.
Adult symptoms
Adults with hypothyroidism usually suffer from an acquired form of the disease. Possible symptoms include:
- Exhaustion, weakness, reduced efficiency
- listlessness, apathy, depressiveness
- Sensitivity to cold
- reduced sweat production
- slowed heartbeat and thus low pulse rate
- slight to moderate weight gain
- Constipation
- Concentration and memory disorders
- slowed thinking or speech
- dry, brittle hair
- cool, dry, scaly skin, orange-yellowish discoloration (especially on palms and soles)
- doughy skin swellings, especially on the face and around the eyes
- dull expression
- hoarse voice, swollen tongue
- enlarged thyroid gland (“goiter” = goiter)
- slowed reflexes
- Cycle disorders, limited fertility
- Erectile dysfunction
Myxedema and myxedema coma
The doughy skin swellings seen in many hypothyroid patients, especially around the eyes but also on other parts of the body, are called myxedema. They are caused by the pathological deposition of special carbohydrate compounds (glycosaminoglycans) in the subcutaneous tissue. A rare but life-threatening complication of severe hypothyroidism is myxedema coma. It occurs especially in older sufferers whose hypothyroidism has been untreated or inadequately treated for years. If an additional stress (for example infection, hypothermia, myocardial infarction, accident, surgery) is then added, this can become a trigger factor and trigger a myxedema coma. Its symptoms include:
- Myxedema (not present in every myxedema coma!).
- extreme weakness
- severely lowered body temperature
- slowed, respectively too shallow breathing
- slowed heartbeat
- slowed, weakened reflexes
- increasing drowsiness up to coma
A myxedema coma is a medical emergency that requires the fastest intensive medical treatment – the risk that the affected person will die is high!
Symptoms in seniors and senior citizens
In older people with hypothyroidism, basically the same symptoms as in other adults are possible. However, their symptoms are often not very pronounced and are easily overlooked or simply blamed on age. In addition, older people with hypothyroidism may also develop less typical symptoms, such as weight loss, confusion, or decreased appetite.
Symptoms in children
Babies born with hypothyroidism show the following symptoms:
- Drinking Laziness
- Constipation
- Lack of movement
- prolonged neonatal jaundice
If left untreated, the child’s further mental and physical development will be delayed. Possible consequences include short stature, impaired speech development, hearing loss, mental retardation and delayed puberty.
Hypothyroidism – Diagnosis at the USZ
If we suspect acquired hypothyroidism in a child or adult based on the symptoms described in the initial consultation (medical history), a blood test can provide clarity. Such an examination is also routinely done in newborns to be able to treat any congenital hypothyroidism at an early stage. The initial focus of the blood test is on the concentration of the thyroid-stimulating pituitary hormone TSH. If its blood value is elevated, this indicates hypothyroidism. Then it depends on the concentration of fT4, i.e. “free” thyroxine (not bound to a protein). The combination of both measured values is interpreted as follows:
- TSH increased, fT4 decreased: There is a manifest hypothyroidism, more precisely: a manifest primary hypothyroidism (in secondary and tertiary hypothyroidism the TSH as well as the fT4 is decreased, in tertiary hypothyroidism additionally the TRH level).
- TSH elevated, fT4 normal: latent hypothyroidism is present, i.e. a “hidden” hypothyroidism with (still) normal thyroid hormone concentration. Over time, this can develop into manifest hypothyroidism – but it doesn’t have to.
By the way: The second thyroid hormone (triiodothyronine, T3) is not suitable for diagnosing hypothyroidism – its measured value is often normal in primary hypothyroidism.
Hypothyroidism: prevention, early detection, prognosis
You can prevent hypothyroidism caused by iodine deficiency by making sure your iodine intake is adequate. How much iodine the body needs depends mainly on age. Pregnancy and lactation also influence the iodine requirement. The main source of iodine in Switzerland is table salt fortified with iodine. Cow’s milk and products made from it also contribute to the iodine supply in this country, especially for children. According to studies, Swiss schoolchildren are generally sufficiently supplied with the important trace element. In contrast, many young children, women of childbearing age, pregnant women and breastfeeding mothers consume less iodine than recommended. To detect congenital hypothyroidism early, all newborns are tested for hypothyroidism (blood test). If the test is positive, drug therapy can be started immediately to ensure the healthy development of the child.
Hypothyroidism – course and prognosis
The course of hypothyroidism depends on its cause. Hypothyroidism due to autoimmune thyroiditis (chronic lymphocytic thyroiditis, Hashimoto’s thyroiditis) is the most common: symptoms develop only gradually. This is because thyroid tissue is destroyed only slowly. In addition, the remaining thyroid gland can compensate for cell loss for a long time by increasing hormone production. After a certain point, however, this is no longer possible. The amount of hormone produced is then no longer sufficient, so that symptoms increasingly develop.
However, with the intake of thyroid hormones, the disease can usually be managed without any problems. Symptoms may appear more quickly in acquired hypothyroidism of a different cause, such as when the thyroid gland must be partially or completely removed due to a tumor. Here, too, the missing amount of hormone must be replaced with medication. Then, as a rule, complaints such as constipation, fatigue and dry skin disappear. In the case of congenital hypothyroidism, hormone replacement therapy must be started as soon as possible after birth. Otherwise, there is a risk of severe growth and development disorders.
