Located in front of the neck, the thyroid gland is the largest endocrine organ in the body, and its main function is to synthesize and secrete thyroid hormones. Hyperthyroidism refers to a clinical syndrome in which the synthesis and secretion of thyroid hormones by the thyroid tissue due to a variety of causes causes, resulting in increased excitability and hypermetabolism of the nervous, circulatory, digestive and other systems.
Causes and classification of hyperthyroidism
Depending on the etiology, hyperthyroidism is divided into several types, the most common is toxic diffuse goiter (Graves disease, about 80%), others are toxic multinodular goiter (Plummer disease, about 10%), autonomous high-functioning thyroid adenoma (about 5%), drug hyperthyroidism (levothyroxine sodium, amiodarone and other iodine-containing drugs), chorionic gonadotropin (HCG)-associated hyperthyroidism, pituitary hyperthyroidism (also called "secondary hyperthyroidism") and so on.
In addition, in the early stage of subacute thyroiditis, chronic lymphocytic thyroiditis (Hashimoto thyroiditis), after radioactive iodine therapy, etc., due to the destruction of thyroid follicles, thyroid hormone spillage, resulting in elevated blood thyroid hormone levels and hyperthyroidism, clinically called "destructive thyrotoxicosis".
However, this "hyperthyroidism" is mostly temporary and can be converted into hypothyroidism later on. Therefore, in the strict sense of the word, it is not true hyperthyroidism, because the thyroid iodine uptake rate and synthetic function of such patients are reduced.
What are the clinical manifestations of hyperthyroidism?
Typical symptoms of patients with hyperthyroidism include heat intolerance, hyperhidrosis, palpitations, polyphagia, wasting, "hyperbolite syndrome" and "sympathetic excitation symptoms" such as excitement, impatience, irritability, hand tremor, and insomnia. In addition, most patients have positive signs such as goiter, protruding eyes, and pre-tibia myxedema.
It should be noted that the symptoms of hyperthyroidism in the elderly are often atypical, and even contrary to the typical hyperthyroid symptoms, they are manifested as loss of appetite, taciturnness, low mood, indifferent expression and so on.
What tests should be done to confirm hyperthyroidism?
This includes thyroid function measurements and related tests around the cause of hyperthyroidism.
Thyroid function tests
Used to determine the presence or absence of hyperthyroidism. When patients have elevated levels of total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4), and free thyroxine (FT4), and decreased levels of thyrotropin (TSH), they are diagnosed with "hyperthyroidism" (specifically, "thyrotoxicosis").
The cause may be due either to an increase in the synthesis of thyroid hormones by the thyroid gland itself (true hyperthyroidism) or to the destruction of thyroid tissue, resulting in increased release of thyroid hormones within the follicle (i.e., "destructive thyrotoxicosis").
In addition, if the patient has elevated TT3, FT3, TT4, FT4, normal or mildly elevated TSH, "pituitary hyperthyroidism" should be highly suspected, and pituitary magnetic resonance imaging may reveal pituitary hyperplasia or adenoma.
Thyroid autoantibody testing
Thyroid autoantibodies, including thyroid peroxidase antibodies (TPOAb), thyroglobulin antibodies (TGAb), and thyrotropin receptor antibodies (TRAb), are primarily used to identify the cause of hyperthyroidism.
TPOAb and TGAb are "destructive" antibodies that destroy thyroid follicle cells and increase thyroid hormone release, which are significantly elevated, considering that transient "hyperthyroidism" may be caused by autoimmune thyroiditis (e.g., Hashimoto thyroiditis). If TRAb is elevated with TPOAb and TGAb, it may be Hyperthyroid Hashimoto with Graves disease.
The thyroid gland sucks 131 iodine rates
This test is mainly used to distinguish "Graves disease" from "early subacute thyroiditis". Both can present with symptoms of hyperthyroidism, but the thyroid 131 iodine rate is increased and the peak moves forward in "Graves disease", while the thyroid 131 iodine rate is reduced in "subacute thyroiditis", accompanied by fever, thyroid pain, and significantly accelerated erythrocyte sedimentation rate (ESR).
Thyroid ultrasound
Knowing the presence or absence of enlarged thyroid glands and nodules can assist in the diagnosis of "toxic multinodular goiter" and "thyroid autonomic high-functioning adenomas".
Thyroid nuclide scan (ECT)
In patients with hyperthyroidism with nodules, isotopic ECT scans can help detect hyperthyroidism due to highly functional adenomas. For those who intend to be treated with 131 iodine, it can also help calculate the dose of 131 iodine required.
Other tests
As mentioned earlier, hyperthyroidism can affect various systems throughout the body, such as the digestive system, blood system, cardiovascular system, etc., resulting in abnormal liver function, leukopenia, electrolyte disorders (such as hypokalemia), tachycardia, atrial fibrillation and so on. Therefore, after the diagnosis of hyperthyroidism, it is also necessary to check the blood routine, liver function, electrolytes, electrocardiogram, etc., to understand whether the patient has leukopenia, abnormal liver function, hypokalemia, arrhythmias and other symptoms, so as to facilitate the evaluation of the disease and guide treatment.
What are the dangers of hyperthyroidism?
Hyperthyroidism brings patients not only changes such as hyperphagia, weight loss, palpitation, hyperhidrosis, irritability, sudden eye irritability, and goiter, but also causes damage to target organs in various systems throughout the body, for example, damage to the heart, leading to hyperthyroid heart disease (tachycardia, atrial fibrillation, myocardial hypertrophy, heart failure, etc.); damage to the liver, resulting in abnormal liver function; involvement of the gastrointestinal tract, causing intractable diarrhea; involvement of the hematopoietic system, resulting in leukopenia; involvement of the nervous system, causing periodic paralysis, muscle weakness; affecting the reproductive system, Causes menstrual irregularities and infertility in women.
In addition, if the condition is not well controlled, it can also lead to serious complications such as blindness, symptomatic psychosis, hyperthyroidism and crisis, and even life-threatening.
How is hyperthyroidism treated?
Because iodine is the raw material for the synthesis of thyroxine, patients with hyperthyroidism should avoid eating high-iodine foods such as kelp and seaweed, and eat uniodized salt (except for pregnant women with hyperthyroidism).
There are three treatment options for Hyperthyroidism in Graves:
1. Antithyroid drug (ATD) treatment. The domestic mainstream treatment plan has an accurate, safe and non-traumatic effect, and the disadvantage is that the treatment course is long and the recurrence rate is high;
2. Radioactive 131 iodine therapy. The efficacy is good, but it is prone to hypothyroidism, and most patients need to take Yomethylol for life;
3. Surgical treatment. Indicated for severe enlargement of the thyroid gland, symptoms of compression or suspicion of malignancy or retrosternal goiter.
Destructive thyrotoxicosis usually requires only symptomatic treatment (e.g., oral β receptor blockers) and generally does not require antithyroid drug therapy, and radioactive iodine-131 and surgery are contraindicated.
Source: Endocrine Channel of the Medical Community
Edited by: Yeah Reviewer: Xiao Ran