Diagnosis of diffuse toxic goiter

With sufficient severity of clinical symptoms, the diagnosis of diffuse toxic goiter is beyond doubt. A correct and timely diagnosis is assisted by laboratory tests. Diffuse toxic goiter is characterized by an increase in the basal level of thyroid hormones and a decrease in TSH. Usually the basal level of T _{3 is} increased to a greater extent than the T ₄ level . Sometimes there are forms of the disease, when T _{3 is} higher, and thyroxine, common and free, within the limits of normal vibrations.

In doubtful cases, when T ₃ and T _{4 are} elevated insignificantly and there are suspicions of thyrotoxicosis, it is useful to conduct a test with rifatiorone (TRH). The absence of an increase in TSH with the introduction of TRH confirms the diagnosis of diffuse toxic goiter.

An increase in the basal level of TSH in diffuse toxic goiter is detected in those rare cases when hyperthyroidism is caused by the TTG-producing adenoma of the pituitary gland. Against the background of elevated levels of T ₃ and T ₄ will be determined by the highest TTG.

When diagnosing diffuse toxic goiter, determination of antibody titer to thyroglobulin, microsomal fraction is of great importance.

An indirect immunofluorescent method for the determination of antithyroid antibodies has been developed. Using this method, four types of antithyroid antibodies (antibodies to microsomal antigen, thyroglobulin, nuclear antigens and the second colloid antigen) can be detected in the blood of patients with diffuse toxic goiter. In their works, SL Vnotchenko and GF Aleksandrova showed that classical antithyroid antibodies are markers of the pathological process in the thyroid gland.

The activity of thyroid-stimulating immunoglobulins (TCI) is determined by the biological method for the growth of human cytomegal cAMP sections.

In addition to the biological method, the method of determining immunoglobulins inhibiting the binding of TSH is used. The most reliable information is provided by their combination with the simultaneous determination of TSH in the blood. As studies have shown, TI are detected in 80-90% of cases in untreated patients with diffuse toxic goiter. The magnitude of their percentage does not determine the severity of thyrotoxicosis, does not correlate with the level of thyroid hormones, but can serve as a criterion for the duration of drug therapy. Discontinuation of treatment at a thyroid-stimulating level of immunoglobulins above 35 / o leads to a relapse of the disease. Patients receiving thyreostatic therapy, apparently, should determine the level of TSI at the beginning of therapy and before the expected cancellation of the maintenance dose of the drug. At a long-term elevated level, it is advisable to refer patients to surgical treatment. The maintenance of a high TII is a risk factor for recurrence of the disease. After adequate treatment of thyrotoxicosis with thyreostatic drugs or radioactive iodine, the TSI titer decreases in half of the patients, after subtotal resection of the thyroid gland - in 83%. Given the transplacental penetration of TGI, the definition of the indicator may have a diagnostic value in pregnant women to determine the risk of congenital hyperthyroidism.

In recent years, a radioisotope study of thyroid function has been used much less frequently in connection with the possibility of determining the level of thyroid hormones and TSH. The method is based on the ability of the thyroid gland to selectively accumulate iodine. The evaluation of its function is based on the rate of iodine uptake, its maximum accumulation and the rate of decline in activity. Radioactive iodine ( ¹³¹ I) is administered intramuscularly in an indicator dose equal to 1 μCi. Determination of activity after 2 and 4 hours shows the rate of its absorption, after 24-48 hours - the maximum accumulation, after 72 hours - the rate of decline.

Absorption of I in disorders of thyroid function,%

Time of determination, h	The rate of fluctuation	Easy hyperthyroidism	Severe hyperthyroidism	Euthyroid goiter	Hypothyroidism
2 4 24	4.6-13 5.32-22 10.0-34	11-37 14.3-40 25-57	15-69 30-75 31-80	4.4-19 7.3-27 11-37	1-5.8 1-5.6 0.6-9

In healthy people, the maximum seizure of radioactive iodine occurs by 24-72 hours and is 20-40% of the indicator dose. In hyperthyroidism, the capture numbers are usually increased depending on the degree of activity of the thyroid gland, more than 40% after 24 hours. In hypothyroidism, the seizure of ¹³¹ I, as a rule, does not exceed 15% of the indicator dose. In evaluating the results of this test, it must be remembered that many drugs can reduce to some extent the seizure of ¹³¹ I by the thyroid gland (salicylates, bromides, thyreostatics, iodine compounds such as enteroseptol, mixase, valocordin, some antibiotics, sulfonamides, mercury diuretics , derivatives of rauwolfia, estrogens, glucocorticoids, adrenaline, many hypoglycemic drugs). Radiocontrast iodine-containing drugs can suppress the capture of ¹³¹ I to the hypothyroid level for a period of several weeks to several years. In connection with the above, low absorption figures have no diagnostic value without evaluation of clinical manifestations. The diagnostic value of the described study is enhanced by using the technetium isotope - ^99m Tc.

Radioisotope scanning (scintigraphy) of the thyroid gland allows revealing a functionally active tissue in it, determining the shape and dimensions, and the presence of nodes. In addition, this method can help detect ectopic areas of thyroid tissue that capture isotopes. The scan is performed 24 hours after taking 1-5 μCi ¹³¹ I or 2-3 μCi ^99m Tc. For diffuse toxic goiter (Graves' disease), an enlarged image of the thyroid gland with increased isotope capture is characteristic.

Ultrasound examination allows to determine the size and volume of the thyroid gland, the features of its echostructure. In hyperthyroidism caused by autoimmune processes, a diffuse decrease in the echogenicity of thyroid tissue is detected.

Of non-specific biochemical indicators of blood should be noted hypocholesterolemia, moderate hyperglycemia.

If there is a characteristic symptomatology of thyrotoxicosis, the diagnosis of diffuse toxic goiter is not very difficult. It is more difficult to put the right diagnosis in cases where the symptoms of a violation of any one system predominate, for example, the cardiovascular, gastrointestinal tract or the psyche, and it is necessary to differentiate diffuse toxic goiter from the corresponding diseases. Difficult diagnosis in elderly patients, when, in addition to the symptoms of thyrotoxicosis, accompanying chronic diseases worsen.

With mild forms of thyrotoxicosis, a physician should conduct differential diagnosis with vegetovascular dystopia. Persistent tachycardia, independent of position of the patient at rest, increased T ₃, T ₄, increased numbers of absorption of thyroid isotopes favor the hyperthyroidism.

Thyrotoxicosis of moderate severity usually does not cause difficulties in diagnosis. However, in the absence of an increase in the thyroid gland, eye symptoms and the presence of predominant disorders from the cardiovascular system, there is a need for differential diagnosis with rheumatic myocarditis, heart defects, tbc-intoxication. The diagnosis is confirmed by an increase in the content of thyroid hormones, increased absorption of I, increased size of the gland.

In severe form, when practically all internal organs and systems are involved in the process, a differential diagnosis with pituitary cachexia, organic lesions of the liver, kidneys, cardiovascular system, miastenia gravis is required. In addition to the studies mentioned above, the presence of tropic hormones of the pituitary gland, the function of the liver and kidneys; a liver scan is performed, as well as a test with proserin, which allows to exclude myasthenia gravis.

Symptoms in toxic adenoma are not significantly different from those with diffuse toxic goiter (Graves' disease), with the exception of exophthalmos, which is practically not found in adenoma. The scintigram determines the absorption of the isotope at the place of the palpable seal with reduced absorption or absence of it in the surrounding tissue. With the introduction of exogenous TSH, the isotope concentration in previously non-accumulating areas of the gland occurs, which makes it possible to differentiate the toxic adenoma from the anomaly of the development of the thyroid gland.

Hyperthyroidism with thyroiditis de Kerven, or subacute thyroiditis is characterized by a low absorption of the isotope. In this case, it is advisable to determine the level of thyroglobulin. For example, with an increase in thyroid hormones and low digestion values of ¹³¹ I with the thyroid gland, the increased level of thyroglobulin is characteristic of subacute thyroiditis, and a low level for thyrotoxicosis.

Hyperthyroidism due to trophoblastic tumors may be suspected if there is an anamnesis of a recent pregnancy, a tumor and a high level of chorionic gonadotropin.

[1], [2], [3], [4], [5]