The functional autonomy of the thyroid gland - causes, symptoms, diagnosis and treatment

In order to maintain normal levels of thyroid hormones (thyroxine - T4 and triiodothyronine - T3) must be adequate intake of iodine, which is an integral part of their molecules. In the context of long-lasting iodine deficiency, in violation of adaptation mechanisms of developing the functional autonomy of the thyroid gland with persistent hypersecretion of thyroid hormones. The functional autonomy of the thyroid gland is found mostly in people older than 50 years and is the most common and clinically significant cause of hyperthyroidism in iodine deficiency regions.

The functional autonomy of the thyroid gland can be unifokalnoy (with a solitary self-education - tireotoksicheskaya adenoma), multifocal (multiple autonomous entities volume - multinodal toxic goiter) and disseminated (diffuse arrangement in gland tissue thyrocytes autonomously functioning). Most often functionally autonomous thyroid tissue is included in the nodules, about 20% of cases - disseminated throughout the thyroid gland.

In the absence of hyperthyroidism functional autonomy of the thyroid gland is considered to be compensated, if any - decompensated.

TSH conditions of iodine deficiency helps maintain production of thyroid hormones to normal levels. Status chronic hyperstimulation of the thyroid gland results in thyroid tissue hyperplasia and diffuse enlargement of the gland (diffuse euthyroid goiter). At the same time receive a preferential growth of cells with high proliferative potential, actively dividing and forming more nodules (nodular and multinodular euthyroid goiter).

Due to the delay of reparative processes in the genetic apparatus of dividing cells arise activating somatic mutations (TSH receptor gene, a-subunit of the adenylate cyclase cascade), causing persistent activation of thyroid hormone synthesis, independent from the regulatory action of the pituitary, t. E. The functional autonomy of the thyroid gland.

In the initial stages of the functional autonomy of the thyroid gland are formed "hot sites", but you can continue euthyroid state and normal levels of TSH (compensated form). Gradually, in the context of the ongoing iodine deficiency, the amount of autonomous thyroid tissue increases exceeds a certain threshold - formed multinodal toxic struma with signs of subclinical and overt hyperthyroidism then. This results in the suppression of secretion of TSH and decrease the absorption of iodine intact the surrounding tissue of the thyroid gland (decompensated form of functional autonomy). The process of forming the functional autonomy of the thyroid gland in the conditions of mild and moderate iodine deficiency takes many decades.

diffuse toxic goiter). A distinctive feature of hyperthyroidism when the functional autonomy of the thyroid gland is a long subclinical followed by the gradual development of symptoms of hyperthyroidism, lack of endocrine ophthalmopathy, scanty atypical clinical picture of the disease in old age. In euthyroid and subclinical functional autonomy of the thyroid gland may remain asymptomatic; compensated form of the disease is usually detected only when the scintigraphic studies.

Among the signs of decompensated functional autonomy of the thyroid gland can distinguish low-grade temperature, poor tolerance of heat, sweating, weight loss, muscle wasting and weakness, irritability, anxiety, insomnia, edema, cardiovascular disorders, stomach disorders.

Overt thyrotoxicosis at a functional autonomy of the thyroid gland is shown the progression of cardiac arrhythmias (sinus tachycardia, atrial fibrillation), increased heart rate, elevated blood pressure, myocardial dystrophy, the development of heart failure.

thyroid function (determination of TSH, T3 - and T4 - free, anti-TSH receptor in the blood), ultrasound, scintigraphy and fine needle aspiration biopsy of thyroid nodules with cytologic examination.

In the case of the functional autonomy of the thyroid gland with subclinical hyperthyroidism marked decrease in TSH, normal values ​​of T4 and T3; in severe thyrotoxicosis - with a decrease in TSH levels of T4 and T3 are increased.

With the help of ultrasound and Doppler thyroid determine its amount, the presence of nodules and acceleration of blood flow. The amount of autonomous units of 15 ml (3 cm in diameter) is considered critical in terms of the development of hyperthyroidism.

Thyroid scintigraphy (including supressionnaya while taking thyroxine) reveals all three functional autonomy, to evaluate the functional activity of the surrounding thyroid tissue.

The differential diagnosis of a thyroid gland is performed with diffuse toxic goiter disseminated type of functional autonomy. When the thyroid gland nodes greater than 1 cm in diameter perform fine-needle aspiration biopsy under ultrasound guidance with cytology punctate, allowing 80% of the tireotoksicheskuyu differentiate high-grade adenoma from adenocarcinoma.

Endocrinology there is no single approach to the treatment of the functional autonomy of the thyroid gland: depending on the specific situation applied conservative and surgical methods of treatment with radioactive iodine - either alone or in combination with each other.

When compensated functional autonomy of a thyroid gland has shown the tactics of active surveillance with an annual patient survey endocrinologist and a ban on the introduction of iodine preparations.

In decompensated functional autonomy of the thyroid gland and the development of hyperthyroidism in preparation for radioiodine therapy or surgery carried out medical treatment with antithyroid drugs - tireostatikami (Mercazolilum, propitsilom) to achieve a euthyroid state.

Surgical intervention is indicated for nodular and multinodular toxic goiter with autonomously functioning tissue volume of more than 3 cm in diameter. Type of transaction depends on the prevalence of functional autonomy of the thyroid gland and may vary from the subtotal resection of the thyroid gland to total thyroidectomy. When tireotoksicheskoy adenoma after thyrotoxicosis compensation perform removal of the affected gland isthmus doli (gemitireodektomiyu).

The method of choice when the functional autonomy of the thyroid gland is considered therapy with radioactive iodine (I-131) that Deplete gipersekretiruyuschie cells that gradually lowers the level of thyroid hormones.

After surgery and radioiodine therapy may develop hypothyroidism requiring life-long purpose replacement therapy with L-thyroxine dose to age.

iodine deficiency disorders, including functional autonomy of the thyroid gland, observed with a decrease in iodine intake below the recommended standards, their prevention is to conduct general (iodization of edible salt) and individual iodine prophylaxis (especially in children, pregnant and lactating women). The daily requirement of iodine as a function of age is 100 to 200 micrograms.

Timely detection and adequate treatment of the functional autonomy of the thyroid gland is particularly important to prevent the risk of complications to the cardiovascular system, central nervous system and other organs.