Diagnostic programs for diseases of the thyroid gland

In order to conduct rational treatment, it is necessary to determine the morphological changes in the thyroid gland and the level of endocrine function of all glands that regulate iodine metabolism in the body.

The examination program of the patient should be consistent with the basic clinical and radiological syndromes. It is advisable to distinguish the following syndromes:

1. diffuse enlargement of the thyroid gland - diffuse goiter (euthyroid or toxic);
2. toxic nodular goiter (toxic adenoma of the thyroid gland);
3. benign volumetric education in the thyroid gland;
4. Malignant volumetric formation in the thyroid gland;
5. hypothyroidism.

In most cases, radionuclide studies begin with the delineation of hyper, eu, and hypothyroid states by radioimmunological determination of the level of thyroid hormones in the blood. Elevated concentrations of T4 and T3 are characteristic of hyperthyroidism, a decreased concentration for hypothyroidism.

First of all, determine the total thyroxin, i.e. The total amount of the hormone (both connected with the transport protein - TSG, and in a free state in the blood - CT4). The normal concentration of T4 in the blood ranges from 70 to 150 nmol / l. Concentration below 70 nmol / l indicates hypothyroidism, and above 150 nmol / l - about hyperthyroidism. Since the main active fraction of T4 is its unbound part, determining its concentration is important for establishing the activity of thyroxin. In healthy people, the concentration of CT4 in the blood is vanishingly small, only 10-20 nmol / L. As in the determination of total thyroxin, a decrease in the content of CT4 indicates hypothyroidism, and an increase in hyperthyroidism.

The determination of T3 is less important than T4. Determine the total T3 and free T3 (CT3). Normally, the T3 content is 1.3-9.5 nmol / L, CT3 is 3-10 nmol / L. Excess of proper values is characteristic of hyperthyroidism, a decrease in hypothyroidism. Data on the T4 content are more reliable, but the determination of the T3 concentration allows us to identify a special form of hyperthyroidism - the so-called T3 - thyrotoxicosis. It is not so rare - in 5-10% of patients with thyrotoxicosis.

In clinical practice, there are cases when at a normal concentration of T, a decrease in the T3 content is observed. In such cases, diagnosed with "low T3 syndrome". It develops under various systemic diseases, liver and kidney deficiency malignant tumors, starvation, burns, extensive surgical interventions.

To assess the functional state of the thyroid gland, it is important to determine not only the content of T3 and T4, but also the concentration of TSH. In healthy people, it is 0.36-0.42 μmol / l. The level of TSH increases in pregnancy, in newborns, when using estrogens and oral contraceptives. Decrease in the level of TSH is observed in diseases of the kidneys, the use of androgens and prednisolone. A special role in the clinic was acquired by calculating the ratio of total thyroxine to TSH. The T4 / TSG index makes it possible to clearly distinguish between eu-, hypo-and hyperthyroid states, even with a change in the concentration of transport proteins. A number of other indices are also proposed. Among them, the "integral index" (AI): II = (CT) + CT4) / CTTG, where CT5 is the normalized value of the total T3 level (2.38 nmol / L x 100%); CT, is the normalized level of the total thyroxine level (90.0 nmol / L x 100%), CTGT is the normalized value of tirotropine (4.46 mE / L x 100%).

In case of impossibility of carrying out radioimmunological analysis, and also if necessary to establish the state of intra-thyroid iodine exchange, radiometry of the thyroid gland is performed.

Diffuse goiter

There is a diffuse increase in the entire thyroid gland in the absence of individual palpable nodes and diffuse-nodular goitre when one or more nodes develop in the enlarged organ. In both forms, the gland function can be normal, strengthened, or weakened.

On radiographs with diffuse goiter, an enlarged thyroid gland with a preserved acoustic structure is revealed. Echogenicity of the gland tissue is usually lowered, but at the same time more coarse structures are distinguished - connective tissue strands against follicular rearrangement. Scintigrams confirm a diffuse uniform enlargement of the gland. Contours of the gland are always convex. The increased intensity of the image is observed with the enhanced function of the thyroid tissue. In large craws, focal formations, including cysts, are often identified. With thyroiditis, the gland is also enlarged, but the RFP is unevenly distributed, although there are usually no clearly defined sites.

Sometimes the thyroid gland is located behind the breastbone ("squamous goiter"). The shadow of this goiter appears on radiographs and especially on the tomograms. Scintigrams allow us to distinguish it from tumor formation in the mediastinum.

[1], [2], [3], [4]

Toxic nodal goiter

With nodular lesions of the thyroid gland, it is advisable to start the study with sonography. Ultrasound scanning can confirm the presence of nodes in the gland, establish their macromorphological structure, distinguish them from cysts. The next stage of delineation of nodal formations is scintigraphy. Most of the nodal formations, with the exception of toxic adenoma, give on the scintigraph a defect accumulating RFP - a "cold" focus. The substratum of the "hot" focus is usually a toxic adenoma - a benign formation, in which there is a clinical picture of thyrotoxicosis. Toxic adenoma of the thyroid gland is focal hyperplasia of thyroid tissue. In sonography, it is identified as a single, clearly quoted node with a reduced echogenicity, on scintigraphs it determines the "hot" focus. In this case, the remaining sections of the gland do not accumulate RFP or it is very small in them. Proof of the toxic adenoma is the stimulation test: after the administration of thyrotropin on scintigraphs, an image of all other parts of the thyroid gland appears.

Often, with a toxic adenoma, a "suppression" test is also used. It allows to establish whether the function of the thyroid gland and adenoma depends on the concentration of the pituitary hormone circulating in the blood - thyrotropin. To this end, the patient is administered thyroid hormones - T3 or T4. If the function of the gland and nodal education in it depends on the pituitary gland, then on repeated scintigrams there is a significant, up to 50% reduction in accumulation of RFP. At the same time autonomously functioning nodes, including toxic adenoma, do not react to the administration of thyroid hormones.

Benign nodal education

In the thyroid gland there are various benign forms of nature: cysts, adenomas, nodes with certain forms of colloid goiter, areas of limited thyroiditis, scarring fields. All of them on the scintigrams determine the area in which the RFP does not accumulate or accumulates very weakly, i.e. A "cold" node. Based on the results of radionuclide research, it is difficult to establish its origin, and sometimes it is impossible. In this case, the diagnosis is assisted by clinical data, sonography and biopsy results.

By the nature of the structure, benign lesions are divided into solid, cystic and mixed. A solid node consists of a dense tissue, the cystic is a cavity with liquid contents, and a mixed one includes both dense tissue and cysts.

Sonograms allow you to immediately identify all cystic formations. The cyst is defined as a round or oval body with smooth contours and has a uniform echo-negative effect. The follicular adenoma looks like the formation of a regular rounded form of reduced echogenicity with some structural heterogeneity. The outlines of the adenoma are usually even. The denser areas in it are determined by increased echogenicity; in such cases, a diminished band around the echogen, due to the peri-node edema of the thyroid tissue, can be seen. "Cold" focus with limited thyroiditis gives a site of low echogenicity with blurred outlines and small additional structures inside.

[5]

Malignant volumetric education

A cancer node in the thyroid gland is usually single. On scintigrams it usually appears as a "cold" hearth. The ultrasound picture is not easy for interpretation, as it varies depending on the structure of the tumor. Most often on sonograms you see a node of low echomolarity with fairly clear, but uneven contours. However, there are tumors with increased echogenicity. The image of the node is not uniform: on its background there are areas of different echogenicity. There is no echo-negative rim around the tumor. Instead, very small calcifications in the form of short lines or foci are often visible around the periphery of the node.

Hypothyroidism

There are four forms of hypothyroidism: primary, secondary, tertiary, iodine deficiency. With primary hypothyroidism, hormone formation in the thyroid gland itself was disrupted, with the thyrotropic function of the pituitary gland reduced. Tertiary hypothyroidism is caused by oppression of the hypothalamus. Finally, iodine deficiency hypothyroidism develops with insufficient iodine content in food and water.

In the differential diagnosis of primary and secondary hypothyroidism, a trial with tyroliberin is crucial. When it is carried out twice the level of thyrotropin in the blood - before and 30 minutes after rapid intravenous tyroliberin injection. In the case of normal functioning of the pituitary, the concentration of tyroliberin increases by 15%.

Parathyroid adenoma

Parathyroid glands control all calcium metabolism in the body. Hyperfunction of one or both glands leads to primary hyperparathyroidism. The level of parathyroid hormone in the blood is determined by the radioimmune method. This is a very sensitive reaction, which makes it possible to establish hyperparathyroidism before the appearance of changes in the bones, detected by X-ray patterns. In approximately 80% of cases, hyperparathyroidism is associated with the development of a single parathyroid adenoma. Secondary hyperparathyroidism is usually explained by hyperplasia of both glands in chronic kidney diseases.

The main task of a specialist in the field of radiation diagnosis is the detection of parathyroid adenoma. This can be done using sonography, computer or magnetic resonance imaging and scintigraphy.

On sonograms, a typical adenoma is well delineated and gives an image of reduced echogenicity. It is defined between the posterolateral edge of the thyroid and the common carotid artery. The size of the adenoma is usually up to 1.5 cm.

For radionuclide detection of adenoma, ^99m Tc-pertechnetate must be ^administered. The scintigraphic image with pertechnetate is "subtracted" from the image obtained on a series of scintigrams with thallium.

The increased function of the parathyroid glands leads to a disruption of the mineral metabolism, primarily of the calcium one. The patient develops hyperparathyroid osteodystrophy (Recklinghausen's disease). It has a bright radiologic picture. On regular radiographs, systemic osteoporosis is determined. Gradually, the bundle and thinning of the cortical layer of bones join him. The emergence of single and multiple cysts in different parts of the skeleton. Often it is possible to distinguish between shadows of stones in the kidneys.

[6], [7], [8], [9], [10], [11], [12]