Hypothyroidism is a chronic disease that requires regular medication and check-ups. Thyroid hormone replacement therapy avoids the serious complications of hypothyroidism. What could be the causes of hypothyroidism? What is the manifestation of hypothyroidism? What is the diagnosis and treatment of hypothyroidism?

Hypothyroidism - what is this disease?

Hypothyreosis(hypothyreosis) is a condition in which the production of thyroid hormones is reduced. Thyroid hormone deficiency can negatively affect the functioning of all organs of our body.

The symptoms of an underactive thyroid can vary from organ system to organ. This makes it difficult to make an unequivocal diagnosis, therefore it is necessary to conduct appropriate tests. Hypothyroidism is a common condition, affecting approximately 1-5% of the adult population.

Thyroid - structure and functions

The thyroid gland is a small gland located at the bottom of the neck and resembles a butterfly. The thyroid gland is adjacent to the front of the upper trachea.

Typically the thyroid gland consists of two lobes - the right and the left, connected by a isthmus. The size of a single lobe of the thyroid gland is half the size of the thumb. Some people have an extra thyroid lobe calledpyramidal lobe .

The pyramidal lobe is an anatomical variant which is a remnant of the development of the thyroid gland in the fetal period. Normal thyroid is not visible to the naked eye. Enlargement of the thyroid gland can make its outline clearly defined around the neck. An increase in the volume of the thyroid gland, regardless of the cause of this condition, is called goiter.

The thyroid gland belongs to the endocrine glands and its main task is to produce hormones. The production of hormones takes place in the tiny follicles that make up the thyroid gland.

The follicles of the thyroid gland enable both the production and storage of hormone molecules. Accordingthe body's current needs, the right amount of hormones can be released into the blood at any time.

The main hormones produced by the thyroid gland aretriiodothyronineandthyroxine , denoted by the symbolsT3andT4 .

Thyroxine is the major product of the thyroid gland in quantitative terms, however triiodothyronine - T3 - is the most active thyroid hormone. In order for T4 to act on target tissues, it is transformed into T3. Mutual conversion of thyroid hormones occurs in all tissues of our body. This process is calledconvert .

In addition to follicular cells, there are also so-calledCcells within the thyroid gland. Their task is to produce an additional thyroid hormone -calcitonin . Calcitonin is responsible for the regulation of the body's calcium-phosphate metabolism.

It is worth knowing, however, that hypothyroidism is associated primarily with the deficiencies of the T3 and T4 hormones. Calcitonin deficiency usually does not have serious consequences, because calcium-phosphate metabolism can also be regulated by other hormones.

The thyroid gland, as an organ of the endocrine system, is one of the centers of hormonal regulation in our body. Like other endocrine glands, the thyroid gland does not "decide" on its own about its activity.

The regulation of thyroid function depends on many factors . Two other organs of the endocrine system, the hypothalamus and the pituitary gland, exercise primary supervision over the thyroid gland. Together they form the so-called hypothalamus - pituitary - thyroid axis.

The hypothalamus and pituitary gland, via their own hormones (thyrotropin TRH, thyrotropin TSH), stimulate or inhibit the activity of the thyroid gland.

The concentrations of these hormones in the blood allow the conclusion about the current condition of the thyroid gland. Testing your TSH levels is a simple and useful way to monitor your thyroid function.

Thyroid hormones - how do they work?

After being released into the blood, thyroid hormones find their way into every tissue of our body. T3 and T4 support the metabolism of all organs - they enable growth and stimulate cell activity.

Thyroid hormones support the absorption and transformation of nutrients. Through them, the consumption of oxygen and the combustion of energetic substances inside the cells increases.

They regulate the heart rate, intestinal peristalsis, the functioning of the reproductive system, the filtration function of the kidneys, and the transmission of impulses in the nervous system. Thyroid hormones can also greatly influence our mental state.

Their appropriate concentrationis crucial in the period of growth and development of the organism. Without thyroid hormones, the proper education and maturation of all organs would be impossible.

Hypothyroidism - Causes

Hypothyroidism is a condition in which the thyroid gland produces a reduced amount of hormones in relation to the body's needs. There are many possible causes of hypothyroidism, but their effect is always common -thyroid hormone deficiency .

Hypothyroidism can arise in two main ways:

  • primary
  • secondary.

In primary hypothyroidism , there are abnormalities in the thyroid gland itself. Primary hypothyroidism results from damage, dysfunction, or abnormal development of thyroid cells.

In turnin secondary hypothyroidism , the thyroid gland itself is built properly and is able to perform its functions. Thyroid hormone deficiency results from other, "external" disorders. Secondary hypothyroidism is most often associated with an abnormal function of the pituitary gland, which is the main organ that regulates the functioning of the thyroid gland.

Which is the most common mechanism of hypothyroidism?

Currently, Hashimoto's disease, i.e. autoimmune thyroiditis, dominates among all causes. At the root of this disease is the so-called auto-aggression, i.e. an abnormal reaction of the immune system to the body's own tissues.

As a result of a mistake, your own organ is recognized as foreign, in need of destruction. The body begins to produce antibodies to destroy specific tissue.

In Hashimoto's disease, the thyroid becomes the target organ. Damage to thyroid cells in the course of Hashimoto's disease leads to a permanent deficiency of thyroid hormones.

Hashimoto's disease is nowadays the leading cause of primary hypothyroidism. Other possible causes of primary hypothyroidism include :

  • thyroid malformations,
  • drug-induced thyroid damage,
  • as well as destruction of the thyroid gland as a result of radiation or surgery.

Removal of the thyroid gland may be necessary, among others in the case of neoplastic diseases of this gland. The resulting hypothyroidism is permanent and requires lifelong treatment.

It is also worth knowing that in some diseases there is a temporary "blockage" of the thyroid function, i.e.transient hypothyroidism . This is the case, inter alia, in the case of subacutethyroiditis. In most patients, the organ regenerates over time and normal thyroid function returns.

Hypothyroidism - Symptoms

The symptoms of an underactive thyroid can vary in severity, depending on the level of thyroid hormones and the duration of the disease. In the initial stages, symptoms can be very discreet.

Subclinical Hypothyroidism

The early stages of hypothyroidism often take the form of the so-called subclinical(latent). The slight deviations in the results of hormonal tests, which are then visible, do not cause significant changes in the patient's well-being.

Early symptoms of hypothyroidism include :

  • feeling tired,
  • slight depressed mood,
  • as well as a feeling of coldness, initially affecting mainly the hands and feet.

As hypothyroidism develops, symptoms affect other organs. They result from a general slowdown in metabolism that can affect all tissues.

Other possible symptoms of hypothyroidism:

  • Slowing down the gastrointestinal motility leads to chronic constipation. The slowing down of the heart rate results in increased fatigue and decreased tolerance to exercise.
  • In the course of hypothyroidism, the skin structure changes - it becomes rough and cold, and there may be peeling around the elbows. The nails become weakened and brittle and the hair tends to fall out.
  • Slowing down the metabolism affects the deterioration of the parameters of the lipid metabolism (including an increase in cholesterol) and may lead to an increase in body weight. Weight gain is also due to water retention in the body.
  • Typically in hypothyroidism there is the so-called myxedema, associated with the accumulation of water within the subcutaneous tissue. In the initial stages, the swelling mainly affects the face and eyelid area. Over time, it can also appear in the joints, palm area, and body cavities (pericardium, pleura, peritoneum).
  • Deficiency of thyroid hormones affects the functioning of the reproductive system. Hypothyroidism in both sexes may lead to a decrease in libido and sexual dysfunction, in women additionally to menstrual and ovulation disorders.

Mental disorders may develop in the course of hypothyroidism:

  • depressed mood,
  • depressive states
  • and emotional control disorders.

Hypothyroidism in children - congenital hypothyroidism

A special type of hypothyroidism is congenitalhypothyroidism, which occurs in the earliest stages of human life.

Deficiency of thyroid hormones during fetal life and in early childhood has irreversible consequences - it leads to disorders of brain development, impaired growth and intellectual disability.

The syndrome of symptoms caused by congenital hypothyroidism was called cretinism in the past.

Currently, all newborns born in Poland are screened for this disease. Early diagnosis and immediate treatment prevent complications of the disease, so today there are practically no cases of full-blown congenital hypothyroidism.

Hypothyroidism - complications

The diagnosis of hypothyroidism is an indication for treatment with thyroid hormone preparations. Maintaining the correct levels of hormones allows you to reduce most of the symptoms of the disease and ensure the proper functioning of the tissues.

If hypothyroidism is not diagnosed in time, further development of the disease can have irreversible consequences and even be life-threatening. The most serious consequences of an untreated hypothyroidism are:

  • heart rhythm disturbances (extreme slow heart rate, impulse conduction disturbances in the heart muscle),
  • arrest of intestinal peristalsis,
  • severe depression
  • breathing disorders.

The acute symptom complex caused by severe, untreated hypothyroidism is called a hypometabolic coma.

Metabolic coma is a medical emergency . The following appear in its course:

  • disturbance of consciousness,
  • cardiopulmonary failure
  • and a significant decrease in body temperature.

Hypometabolic coma requires treatment in an intensive care unit.

Hypothyroidism - diagnosis

The basic test that allows for the initial assessment of thyroid function is the determination of the level of TSH in the blood. TSH is a hormone produced by the pituitary gland that stimulates follicle growth and the release of thyroid hormones.The norm of TSH concentration is 0.4-4.0 mIU / l .

The correct concentration of TSH allows to exclude disorders of the thyroid function. Both in the case of increased and decreased TSH levels, additional tests are necessary. It is then necessary to determine free thyroid hormones - the so-called fT3 and fT4 (in some patients the determination of TSH, fT3 and fT4 is performed simultaneously).

In the case of hypothyroidism, blood levels of fT3 and fT4 are lowered .If they are accompanied by a lowered TSH level, we can diagnose secondary hypothyroidism. In this situation, the thyroid gland produces a reduced amount of hormones due to insufficient stimulation by the pituitary gland.

Conversely, if fT3 and fT4 are decreased and TSH is increased, the hypothyroidism is primary . A damaged thyroid gland produces reduced amounts of hormones and the pituitary gland tries to compensate for the deficiency by releasing increased amounts of TSH.

The diagnosis of hypothyroidism is based on the tests of the level of the following hormones: fT3, fT4, TSH. Based on them, treatment should be started and then monitored. Additional tests may be indicated to determine the cause of hypothyroidism, as well as to identify possible complications of the disease.

The test used for imaging the thyroid gland is ultrasonography (USG). Ultrasound allows you to assess the size and structure of the thyroid gland. To diagnose the most common cause of hypothyroidism - Hashimoto's disease - it is necessary to test the antibodies typical for this disease. Increased levels of anti-TPO and anti-Tg antibodies confirm the diagnosis.

Depending on the advancement of the disease and clinical symptoms in a given patient, the doctor may decide to extend the diagnosis. In hypothyroidism, it is worth checking the blood count periodically, as well as the parameters of lipid and carbohydrate metabolism (cholesterol, triglycerides, fasting glucose).

If other complications are suspected, specific additional tests (eg ECG in case of heart disorders) may be necessary. The diagnosis of secondary hypothyroidism is an indication for in-depth hormonal diagnostics, often an imaging examination of the pituitary gland is necessary.

Does hypothyroidism always require treatment?

Untreated hypothyroidism is not always serious. The decision to initiate treatment for hypothyroidism depends on many factors: the presence of clinical symptoms, age, general he alth, and thyroid hormone levels.

If the hypothyroidism is symptomatic, treatment should be started strictly. In the absence of clinical symptoms (latent hypothyroidism), the decision depends mainly on the level of TSH.Supplementation of thyroid hormones is indicated in all patients with TSH levels>10 mIU / l .

If the TSH level is 5-10 mIU / L, treatment is started in the case of previously diagnosed thyroid disease and the presence of additional risk factors (e.g. heart disease).

In the elderly (over 80 years of age), in the case ofslight latent hypothyroidism may be withheld from treatment. However, drugs should be started in the event of the appearance of symptoms of the disease.

More restrictive rules apply to pregnant women. Thyroid hormone deficiency can seriously disturb the development of the fetus, therefore, even asymptomatic hypothyroidism should be treated during pregnancy.The indication for treatment with thyroid hormones during pregnancy is TSH level above 2.5 mIU / l .

Hypothyroidism - rules for administering medications

Regardless of the cause of hypothyroidism, there is one common treatment regimen -thyroid hormone supplementation . The drug for hypothyroidism is primarily L-thyroxine (LT4, Letrox, Euthyrox).

Determining the right dose of hormones requires TSH control tests. Therapy is usually started with low doses of the drug, increased as needed. The first hormone level control tests are performed approximately one month after the treatment is started. After determining the appropriate dose of the drug, it is enough to test the level of TSH, fT3 and fT4 once a year.

Thyroid hormone preparations should be taken on an empty stomach, approx. 0.5

- 1 hour before a meal.

It is worth remembering that some medications limit the absorption of L-thyroxine from the gastrointestinal tract. In the case of simultaneous use of preparations containing iron, aluminum, calcium, or preparations reducing the secretion of gastric acid, a minimum two-hour interval should be kept.

Special principles of treating hypothyroidism apply to pregnant women. It is a period of increased demand for thyroid hormones, therefore it requires an increase in the basic dose of the drug (usually by about 30%, doses should be modified only in consultation with the attending physician).

Additionally, in the case of hypothyroidism, pregnant patients should supplement iodine at a dose of 250 µg / day. Outside of pregnancy, iodine supplementation in hypothyroidism is not necessary (except for a proven deficiency of this element in the diet).

Hypothyroidism - prognosis

Hypothyroidism is a chronic condition that in most cases requires lifelong treatment. Properly diagnosed and treated hypothyroidism is not associated with he alth complications.

Inadequate dosage of thyroid hormones or discontinuation of treatment may lead to irreversible consequences. The treatment of hypothyroidism in pregnant women is of particular importance, as it is a prerequisite for the proper development of the fetus.

  • Subclinical (latent) hypothyroidism - causes, symptoms andtreatment
  • Hyperthyroidism: causes, symptoms, treatment
  • Thyroid diseases: causes, symptoms, tests, treatment

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