Endemic goiter is an enlargement of the thyroid gland, which is caused by insufficient intake of iodine into the body. The disease develops when living in an area poor in this trace element, monotonous diet, lack of individual or group prevention of iodine deficiency. Goiter is manifested by a gradual painless increase in the size of the gland, in the later stages signs of hypothyroidism or thyrotoxicosis are added. Pathology diagnostics includes ultrasound and scintigraphy, CT or MRI of the neck, laboratory determination of the thyroid profile. For treatment, a diet, intake of iodine-containing drugs, complexes of vitamins and minerals are necessary.
The population of all regions of the Russian Federation is at risk of developing iodine deficiency lesions of the thyroid gland. The prevalence of the diffuse form of endemic goiter in the population is about 31%, women get sick 2-3 times more often than men. The nodular variant of pathology is observed in 30% of people 35-50 years old, more than 50% of patients are in the older age group. In practical endocrinology, a big problem is the increase in cases of goiter among children: the risk of the disease is 2% at the age of 1 year, 20-30% at 10 years, 30-50% at 13-18 years.
A key factor in the development of endemic goiter is absolute or relative iodine deficiency. The lack of this trace element of varying severity is registered throughout the country, especially in high-altitude areas and regions affected by pollution during the Chernobyl accident. The average level of iodine consumption by Americans ranges from 40 to 80 micrograms per day, which is 2-3 times lower than the recommended WHO standards.
The formation of goiter is facilitated by strumogenic substances that are contained in food products (cabbage, carrots, radishes) and some preparations. Such components prevent the absorption of iodine by thyroid tissues, cause a compensatory increase in the volume of cells and intercellular matter. Predisposing factors include burdened heredity, excess calcium and fluoride in food, irrational nutrition with low levels of protein and vitamins.
Iodine is the most important substrate for the formation of thyroid hormones triiodothyronine (T3) and thyroxine (T4). In the process of synthesis of one molecule, 3-4 atoms of the mineral are used. In peripheral tissues, the transformation of inactive T4 into active T3 is observed, which is accompanied by the cleavage of one iodine atom and its reverse absorption by the thyroid gland. Iodine is considered a regulator of thyroid hormonal activity and the growth rate of its cells.
With a deficiency of a trace element, intrathyroid proliferation mediators are activated: interleukins, epidermal and insulin-like growth factors. An increase in intracellular inositol triphosphate plays an important role in the pathogenesis of endemic goiter. The stronger the iodine deficiency, the more the growth factors are activated. At first, there is a diffuse increase in the gland tissues, with prolonged subcompensation, single nodes are formed.
According to morphological changes, endemic goiter occurs in 2 variants: diffuse, which is caused by a uniform increase in all parts of the organ, and nodular, characterized by focal neoplasm. For palpatory determination of thyroid enlargement, the WHO classification (2001) is used, according to which 3 degrees of severity of the disease are distinguished:
- 0 (zero). Absence of goiter, the size of each lobe of the organ is less than or equal to the volume of the distal phalanx of the patient’s thumb.
- 1 (the first one). The increase can be detected by palpation of the anterior surface of the neck, but there are no external signs of the disease.
- 2 (second). The presence of goiter is determined by an external examination of the neck in a normal position.
The disease is characterized by a long latent course. Clinical manifestations develop against the background of a significant increase in the volume of the gland, which begins to squeeze the surrounding organs. A person experiences a feeling of pressure and bursting in the neck area, notices a deformation of its contours. When the trachea is compressed, shortness of breath appears, difficulties when trying to take a deep breath. With endemic goiter, there is a dry cough, hoarseness of voice.
Deterioration of general well-being is observed in the complicated course of the disease, when euthyroidism is replaced by manifestations of hyper– or hypothyroidism. With a decrease in thyroid function, nonspecific complaints of weight gain, swelling of the body, muscle weakness are manifested. The skin becomes dry, the hair brittle and dull. Patients complain of increased fatigue, daytime drowsiness.
With hyperthyroidism, patients become nervous, excitable, emotionally unbalanced. There is a persistent heartbeat, tremor of the fingers, weight loss with increased appetite. Neurological symptoms appear as violations of the sequence of thoughts, accelerated speech, decreased concentration of attention. The defeat of the gastrointestinal tract in thyrotoxicosis is characterized by attacks of abdominal pain, diarrhea, rumbling in the intestines.
With prolonged untreated endemic goiter, compensatory mechanisms are depleted. In conditions of iodine deficiency, there is a possibility of deep suppression of hormonal activity, which is manifested by hypothyroidism. In the case of the formation of autonomous nodes in the tissues of the thyroid gland, there is a risk of thyrotoxicosis against the background of uncontrolled synthesis of thyroid hormones. 5-10% of patients with a nodular form of thyroid pathology eventually develop a malignant tumor.
With severe iodine deficiency, 30-70% of the population has a decrease in intellectual functions, in 5-30% of cases there is mental retardation and severe neurological symptoms. Especially dangerous are the phenomena of iodine deficiency for pregnant women: 54.5% of women develop gestosis, 22.7% – fetal hypoxia, 18.2% – the threat of miscarriage. In 10% of children whose mothers suffered from iodine deficiency, goiter develops in utero.
If endemic goiter is suspected, the patient is prescribed an examination by an endocrinologist. The initial reception includes the collection of complaints and anamnesis, clarification of risk factors for iodine deficiency, palpation of the neck to clarify the size of the thyroid gland. The complete diagnostic complex in endocrinology includes the following research methods:
- Ultrasound of the thyroid gland. The presence of goiter is indicated by the volume of the organ more than 18 ml in women, more than 25 ml in men. With the help of sonography, the contours of the gland, the echogenicity of its parenchyma, the uniformity or heterogeneity of the structure are determined. Ultrasound visualizes the volume formation, but does not allow to determine its exact nature.
- Scintigraphy of the thyroid gland. Radioisotope scanning is assigned to assess the functional activity of the organ, to identify nodular formations. By the nature of the accumulation and distribution of radioactive isotopes, it is possible to judge the degree of production and release of thyroid hormones, the presence of autonomous foci.
- CT of the neck and mediastinum. X-ray diagnostics is prescribed to clarify the size of the endocrine organ, to determine the signs of invasion into the surrounding structures. CT is used if there is a suspicion of a malignant nature of the process. If the method is not sufficiently informative, an MRI of the neck is performed.
- Fine needle aspiration biopsy. The puncture of the gland and the collection of material for histological examination are performed under ultrasound control. The study is necessary for nodular thyroid pathology in order to differentiate the benign and malignant process
- Laboratory diagnostics. To assess the thyroid status in endemic goiter, tests for thyroid hormones (thyroxine, triiodothyronine), thyroid-stimulating hormones of the pituitary gland, hypothalamic thyrooliberin are prescribed. The level of calcitonin in the blood serum is determined. To exclude autoimmune causes of pathology, the level of thyroid antibodies is measured.
Endemic goiter must be distinguished from other diseases that are accompanied by an increase in size and altered hormonal activity of the organ. Differential diagnosis is performed with sporadic goiter, Hashimoto’s autoimmune thyroiditis, neoplastic processes (adenoma or thyroid cancer). Occasionally, the disease is differentiated with congenital or genetic defects in the formation and secretion of thyroid hormones.
With endemic goiter, it is recommended to correct nutrition and add food sources of iodine to the diet. Patients need to use special iodized foods. For a good assimilation of the mineral compound, a sufficient content of vitamins A and E, trace elements of iron, zinc, copper is required. For the period of correction of iodine deficiency, a fortified high-protein diet is prescribed.
Non-drug measures to make up for the mineral deficiency will not be enough. In clinical endocrinology, potassium iodide preparations are prescribed for iodine deficiency diseases and the absence of signs of thyrotoxicosis. The dosage of drugs is carried out taking into account the age of the patient, the severity of endemic goiter. In addition to potassium iodide, vitamin and mineral complexes with a high content of iodine are used.
With diffuse euthyroid goiter and the presence of compression syndrome, an operation in the volume of total or subtotal thyroidectomy is indicated, which restores the patency of the trachea and prevents the development of respiratory failure. Surgical removal of a nodular goiter is prescribed for its retrosternal localization, a pronounced cosmetic defect, and the impossibility of excluding a malignant tumor by other means.
Prognosis and prevention
With endemic goiter detected at an early stage, it is possible to completely correct iodine deficiency and stop the proliferation of thyroid cells. The prognosis is favorable for people with diffuse organ enlargement, whereas nodular formations often acquire autonomy and become the cause of thyrotoxicosis. Less optimistic forecasts for patients with the 2nd degree of the disease, the presence of persistent hypothyroidism, compression of the neck organs.
In conditions of total iodine deficiency in the United States, prevention of endemic thyroid pathology becomes important. To obtain a daily allowance of trace elements, it is recommended to replace ordinary table salt with iodized salt, purchase fortified foods: bakery products, dairy products, baby food. Group prevention is carried out for pregnant and lactating women, children and adolescents.