The thyroid gland is a small parenchymatous organ placed in the lower half of the frontal part of neck. Its weight is approximately 20 grams. It belongs to the group of glands with internal secretion, which secrete their hormones directly into the blood. The two main thyroid hormones are thyroxine (T4) and triiodothyronine (T3). Their production regulates the pituitary hormone thyrotropin (TSH). If you reduce the production of T3 and T4, the pituitary gland produces a larger amount of TSH trying to stimulate the thyroid to work better. If the thyroid gland can not do this, TSH level is increasing rapidly which can lead to goiter (an enlargement of thyroid gland).
What is hypothyroidism?
Hypothyroidism is a metabolic disorder caused by decreasing the amount of thyroid hormone in the body, which manifests itself with many symptoms. Very rarely values of T3 and T4 may be normal, or even elevated, and the error is on the tissue cells that have receptors for thyroid hormones and their effect is absent.
Causes and prevalence
The most common cause of hypothyroidism is Hashimoto’s thyroiditis – a chronic inflammation of the thyroid gland.
It is an autoimmune disease in which, due to errors in the recognition, the body produces antibodies to the various constituent parts of the thyroid. These antibodies gradually lead to irreversible damage to the thyroid gland and the slow weakening of its functions. Generally autoimmune diseases are about seven times more common in women than in men, and so is this disease. They can affect all age groups, and very often there is a familial predisposition. It covers a few percent of the population, slightly more common in women of 40-60 years.
Hashimoto’s thyroiditis very often occurs in combination with other autoimmune diseases (e.g. rheumatoid arthritis, lupus erythematosus, diabetes, etc).
At the present time, a very common cause of hypothyroidism is radioactive iodine I- 131, which is sometimes used for the treatment of hyperthyroidism (increased thyroid secretion). Hypothyroidism can be caused by thyroid surgery. It is an inevitable consequence of the complete removal of the gland in the case of thyroid cancer, and often occurs after partial resection of thyroid due to benign tumors, hyperthyroidism, cystic lesions, etc.
Hypothyroidism can be caused by a rare disease of the pituitary gland and the hypothalamus (secondary and tertiary hypothyroidism). It may be caused by radiation of neck, some medications, etc.
Congenital hypothyroidism is a separate condition, which can now be thankfully revealed in the maternity routine determining the values of TSH in the blood of the newborn.
Symptoms
All the symptoms are a consequence of reduced metabolic functions. Patients gain weight, are slow, sleepy, lethargic, constantly they feel cold. They often have constipation, skin becomes pale, and in severe cases edemas and disturbance of the heart occur. The hair is dry and hard to comb, the voice is hoarse because of vocal cord edema, hearing loss manifests, there is a disturbance of menstrual cycles and sterility in men and women.
Especially dangerous is that these symptoms of Hashimoto thyroiditis develop gradually, so that the patients often get used to them. Many of them remain unidentified to the advanced level of the disease. It is important to note that a good part of the patients does not have some discomforts, so hypothyroidism is discovered accidentally.
Tests and examinations
From the blood it is the most important to determine the values of the peripheral thyroid hormones (T3 and T4 ) and TSH, of which a significant increase TSH is the most important indicator of hypothyroidism. The values of T3 and T4 sometimes depend on the amount of proteins that serve as their carriers and can cause falsely elevated values. In these cases it is better to determine the free hormones (FT3 and FT4), unbound to proteins. Direct indicator of slower metabolism is elevated levels of cholesterol in the blood, and its increased value is sometimes the first sign of possible hyperthyroidism. In the case of suspected Hashimoto’s thyroiditis. it is desirable to determine the concentration of antibodies to the thyroid gland. In our conditions, it is possible to determine antibodies to thyroglobulin and peroxidase.
It’s very important to do an ultrasound examination of the thyroid gland to see the quantity and appearance of the tissue of the thyroid gland In Hashimoto’s thyroiditis, thyroid gland is usually very inhomogeneous, hypoechogenic and uneven contours, and conditions after surgery see a significant reduction in the glandular tissue. Sometimes, when the existence of thyroid tissue cannot be established, cintigraphy with Tc – 99m pertechnetate can be performed.
Treatment
Regardless of its cause, in the case of hypothyroidism, hormone replacement therapy for thyroid gland must be undertaken.
On the market there is thyroxine in tablet form, which needs to be taken every morning for at least half an hour before meals. The therapy is introduced gradually, and the required dose of thyroxine is usually defined after a few months of taking the drug . After the introduction of the drug or changing the dose, some time needs to pass in order to create a balance between the pituitary and new levels of thyroxine in blood, so that the thyroid hormones and TSH are determined at least 6 weeks of these changes. It is important to say that it is necessary to cure subclinical hypothyroidism as well (T3 and T4 are normal, elevated TSH).
During pregnancy and during breastfeeding drug is also necessary, provided that the dose needs often to be increased due to increased need for thyroxine. Thyroxine is completely harmless to the fetus.
Prognosis
The prognosis is excellent replacement therapy if taken regularly at a dose prescribed by doctors. Patients should be aware that most often therapy with thyroxine is life-long. In the case of Hashimoto’s thyroiditis, need for thyroxine is usually progressively increased and the dose of the drug should also be rising. In the case of postpartum (maternal postpartum) thyroiditis and inflammation of the thyroid gland, hypothyroidism is usually transient.
Complications
If replacement therapy is properly taken there are no complications. They may occur in the case of not taking the therapy or in case of overdose with thyroxine. In the first case, the symptoms of hypothyroidism deepen which may lead to its worst form – myxedema coma (80 % mortality). If thyroxine is taken in excessive dose, iatrogenic (caused by the drug) hyperthyroidism occurs with all its symptoms (sweating, nervousness, weight loss, tachycardia, etc). It is therefore important that all these patients are under the doctors’ supervision and to control thyroid hormones and TSH at least once a year.
Prevention
In the case of almost all causes of hypothyroidism there are no real preventive measures and its occurrence is virtually impossible to prevent. It is important to recognize it and prevent the occurrence of complications.
In congenital hypothyroidism as a consequence of the non-recognition of the disease cretinism occurs, which is fortunately rather rare today because of early determination of TSH as early as maternity hospitals, resulting in timely initiation of taking replacement therapy in newborns with hypothyroidism.