Hypothyroidism is a condition in which the thyroid gland does not produce enough hormones and causes various symptoms throughout the body.
Thyroxine is a hormone produced by the thyroid gland located on the neck.
It is transported in the body through the bloodstream and helps to maintain the correct body metabolism.
Many cells and tissues of the body need thyroxine to function normally.
Hypothyroidism is the result of an inability of the thyroid gland to produce enough thyroxine.
The result is the slowing down of many bodily functions.
Hypothyroidism can also occur after surgical removal or lesion of the thyroid gland because not enough part of the thyroid gland remains to produce thyroxine.
In contrast, too much thyroxine is produced in those who suffer from hyperthyroidism. The result is an acceleration of many bodily functions.
What are thyroid hormones?
Thyroid hormones are products of the thyroid gland. This gland is located in the lower neck under the Adam’s apple. The gland is located in front of the trachea and resembles a butterfly in shape. It is formed by two wings (lobes) connected to a central part (isthmus).
The thyroid gland needs iodine (which is found primarily in foods such as fish, bread, and table salt) to produce the thyroid hormones.
The two thyroid hormones are:
- thyroxine (T4),
- Triiodothyronine (T3).
They make up 99% and 1% of the thyroid hormones in the blood, respectively.
However, the hormone with the greatest biological activity is T3.
Most T4 hormones are converted to T3 after they are released from the thyroid gland into the bloodstream.
The reference values (normal) of thyroid hormones are:
TSH – from 0.35 to 5.5 μU/ml FT3 – from 2.0 to 4.5 pg/ml FT4 – from 8.0 to 18.0 pg/ml
Thyroid hormone regulation
The production of thyroid hormones depends on another gland located in the brain, the so-called pituitary gland. The pituitary gland, for its part, is regulated by:
- another gland, the so-called hypothalamus,
- the amount of thyroid hormones present in the blood.
When hormone levels drop:
- the hypothalamus releases thyrotropin-releasing hormone (TRH), which sends a signal to the pituitary gland to release thyroid stimulating hormone (TSH) into the bloodstream;
- the pituitary gland releases a hormone (TSH) into the bloodstream to stimulate the thyroid gland to produce the hormones thyroxine (T4) and triiodothyronine;
- the TSH, in turn, sends the signal to the thyroid gland to release thyroid hormones; If there is an interruption at one of these stages, an error in the production of thyroid hormones can lead to a hormone deficiency of the thyroid gland (hypothyroidism).
Thyroid hormones – T4 and T3
The production rate of thyroid hormones is controlled by the pituitary gland. If the amount of circulating thyroid hormone is too low to allow normal functions in the body, the release of TSH in the pituitary gland increases with the attempt to stimulate thyroid hormone production.
In contrast, TSH levels decrease when there is an excessively circulating amount of thyroid hormone because the pituitary gland tries to decrease the production of thyroid hormones.
In patients with hypothyroidism, the level of circulating thyroid hormones is permanently lowered.
Causes of hypothyroidism
Hypothyroidism has several causes, including:
- Hashimoto’s thyroiditis
- thyroiditis or thyroiditis,
- Congenital hypothyroidism or congenital hyperthyroidism
- Surgical removal of part or all of the thyroid gland
- Radiation treatment of the thyroid gland
- There is a connection between celiac disease, type 1 diabetes and thyroid diseases.
According to some authors, celiac patients are three times more likely to develop thyroid disease.
Many people suffer from celiac disease but do not know about it; others are sensitive to gluten, meaning they have mild symptoms when they eat foods containing this substance.
Some doctors advise people with thyroid problems against gluten-containing foods even if they don’t have celiac disease, such as Dr. Mozzi, who developed the blood type diet.
- Some medicines
Rarely, hypothyroidism is caused by too little iodine in the diet or by an abnormality of the pituitary gland.
This disorder usually affects women, hypothyroidism in men is rare, the ratio is 1 to 15.
Causes of primary hypothyroidism
1. Hashimoto’s thyroiditis Hashimoto’s thyroiditis, also called chronic lymphocytic thyroiditis
, is the most common cause of hypothyroidism.
Hashimoto’s thyroiditis is a form of chronic thyroid inflammation and an autoimmune disease.
Normally, the immune system protects the body against external invaders such as viruses and bacteria that can cause illness. However, in autoimmune diseases, the immune system attacks its own body cells and organs.
In Hashimoto’s thyroiditis, the immune system attacks the thyroid gland, causing inflammation and disrupting the ability to produce thyroid hormone.
2. Thyroiditis Thyroiditis
causes a release of the thyroid hormones stored in the thyroid gland. At first, this increases the levels of hormones in the blood, which leads to hyperthyroidism, which lasts for 1 or 2 months.
Most people develop hypothyroidism before the thyroid gland is completely healed.
Different types of thyroiditis can cause hyperthyroidism followed by hypothyroidism:
- Subacute thyroiditis
This condition causes painful inflammation and enlargement of the thyroid gland. Experts are not clear about its cause, but it could be tied to a viral or bacterial infection. This disease usually passes on its own within a few months.
- Postpartum thyroiditis This type of thyroiditis
develops after a woman gives birth.
- Silent thyroiditis This thyroid inflammation is called “silent” because, like postpartum thyroiditis
, it is painless, even though the thyroid gland may be enlarged.
Like postpartum thyroiditis, the silent form is thought to be an autoimmune disease and sometimes develops into permanent hypothyroidism.
3. Congenital hypothyroidism (congenital)
Some children are born with a thyroid gland that is not yet fully developed or not functioning properly.
If left untreated, congenital hypothyroidism can lead to mental retardation and growth retardation. Early treatment can prevent these complications.
4. Surgical removal of the thyroid gland
If part of the thyroid gland is removed, the remaining portion can still produce a sufficiently normal amount of thyroid hormone. However, some people develop hypothyroidism after surgery.
Complete removal of the thyroid gland causes hypothyroidism of the acquired type.
Removal of part or all of the thyroid gland is carried out to treat the following diseases:
- large goiter, that is, an enlarged thyroid gland, which causes swelling on the neck and can interfere with breathing and swallowing;
- Nodules on the thyroid gland are benign tumors, so-called adenomas, which can produce thyroid hormones excessively;
- Thyroid tumor.
5. Radiation treatment for hypothyroidism Radioactive iodine is often used in the treatment of hyperthyroidism
to gradually destroy the thyroid cells. Most people who undergo radioactive iodine therapy develop hypothyroidism. People with Hodgkin’s disease, other lymphomas and tumors of the head or neck are treated with radiation, which can also damage the thyroid gland.
Some medications can interfere with the production of thyroid hormones and lead to hypothyroidism, including:
- Amiodarone, a heart medication
- Interferon alpha, a tumor static agent
- Lithium, a drug in bipolar disorder
- Interleukin-2, a drug for kidney cancer
7. Severe iodine deficiency
This is observed in areas where the diet contains little iodine.
Severe hypothyroidism can be found in 5-15% of the population. For example, it occurs in some parts of:
- in remote mountainous areas, such as the Andes and the Himalayas.
Since iodine is present in table salt and bread, iodine deficiency is rare in Europe.
Causes of secondary hypothyroidism
Hypothalamic and pituitary diseases
If, for some reasons, the pituitary gland or hypothalamus is unable to communicate with the thyroid gland to give instructions on the correct amount of thyroid hormones, the amount of circulating hormones T4 and T3 may be lowered, even if the thyroid gland is working perfectly normally.
- If this hormone deficiency is caused by a disease of the pituitary gland, it is called a “secondary hypothyroidism“.
- If the disease is caused by a disorder of the hypothalamus, this is called “tertiary hypothyroidism“.
What are the risk factors for hypothyroidism?
The most common risk factors for hypothyroidism are:
- female sex and age over 50 years; however, in principle, any person can develop hypothyroidism;
- treatment with radioactive iodine (or other thyrostatics);
- Age, people over 60 years have a greater risk of developing hypothyroidism;
- close relative with an autoimmune disease;
- Radiation exposure;
- Thyroidectomy – surgical partial removal of the thyroid gland.
Symptoms of hypothyroidism
The signs and symptoms of hypothyroidism vary depending on the severity of the hormonal deficit.
As a rule, health problems develop slowly, often over several years.
At first, it is difficult to recognize the symptoms of hypothyroidism or it is assumed that they are age-related, such as:
- Increase in body weight.
If hypothyroidism is subclinical, it means that it is mild and can be asymptomatic.
Over time, the constantly slowing metabolism can cause more noticeable signs and symptoms to develop.
Signs and symptoms of moderate or severe hypothyroidism include:
- Sensitivity to cold
- Stool constipation
- Skin dryness
- Unexplained weight gain, you gain weight even with the same amount of food
- Muscle spasms
- High cholesterol in the blood
- Menstrual cycle stronger than normal or irregular
- Hair loss
- Bradycardia (slow heartbeat)
- Mood swings
Hypothyroidism in newborns
Even though hypothyroidism much more often affects middle-aged women and the elderly, anyone can develop this disease, including infants and newborns.
Initially, children born without a thyroid gland or with a gland that is not functioning properly may have minor signs and symptoms. When newborns suffer from hypothyroidism, the following symptoms may make themselves felt:
- The skin and sclera of the eye are yellowish, i.e. signs of jaundice.
In most cases, this occurs when the child’s liver does not metabolize what’s called bilirubin, which normally forms when the body utilizes old or damaged red blood cells.
- Large, protruding tongue (causes frequent attacks of choking).
- Small stature due to delayed bone maturation.
- Umbilical hernia.
- Swollen face.
As the disease progresses, newborns are at risk of nutritional problems and growth and normal development may be disrupted.
In the case of newborns, the following can also be observed:
- Constipation (constipation)
- Weak muscle tone
- Pronounced drowsiness
If childhood hypothyroidism is not treated, it can cause severe physical and mental delays, even in mild cases.
Hypothyroidism in children and adolescents
As a rule, children and adolescents who develop hypothyroidism have the same signs and symptoms as adults, but it can also be observed:
- Reduced growth, resulting in a small body size
- Delayed development of permanent teeth
- Delay of puberty
- Decreased mental development
Risks and complications of hypothyroidism in pregnancy
Hyperthyroidism in pregnancy can cause some complications, for example:
- Miscarriage (spontaneous abortion)
- High blood pressure (hypertension) and preeclampsia
- Death of the fetus
- Placental detachment
- Premature birth
- Postpartum hemorrhage