1. What is hyperthyroidism?
Hyperthyroidism, is a set of clinical symptoms caused by excessive production of thyroid hormones. Thyroid gland is an odd gland located in the anterolateral lower part of the neck. Hyperthyroidism occurs in 1.6% of women and 0.14% of men.
Thyroid produces three hormones, thyroxine (T4), triiodothyronine (T3), and calcitonin. Calcitonin is produced by thyroid C cells and is responsible for reducing the content of calcium ions in the blood and stops calcium in the bones. Hormones T4 and T3 are controlled by the pituitary hormone thyrotropin (TSH), i.e. when the amount of TSH increases, the levels of T3 and T4 decrease, whereas if the amount of TSH decreases, the levels of T3 and T4 increase. This is a typical feedback characteristic of the regulation of the endocrine system.
T3 and T4 are found in the blood in the so-called free form – fT3 and fT4, from the English word free. Other hormones are associated with plasma proteins such as globulin or albumin. Only free hormones are active and can bind to cellular receptors. T4 in peripheral tissues undergoes dehydrogenation to T3 under the influence of dejodinase enzymes produced, e.g. through the pituitary, liver, kidneys. Most T3 are formed in this way and it is several times more biologically active than T4.
Hyperthyroidism can be divided into
– subclinical, which is asymptomatic or oligosymptomatic, and the concentration of free hormones (T3 and T4) in the blood is normal, there is a decrease in TSH,
– clinically manifest, accompanied by symptoms of overactivity, and the concentration of free hormones in the blood is above the reference values,
– primary, caused by disorder of thyroid hormone secretion,
– secondary, caused by excessive secretion of TSH by the pituitary gland, e.g. as a result of pituitary tumor.
2. Hyperthyroidism – causes
Hyperthyroidism can be caused by:
– Graves-Basedova disease,
– hyperactive nodular goiter (Plummer disease – multiple autonomic bumps, Goetsch’s disease – a single thyroid nodule, scattered micro-throats throughout the thyroid),
– iod-Basedow syndrome, i.e. hyperthyroidism induced by excessive iodine exposure,
– an overactive condition that accompanies other thyroid diseases, e.g. inflammation, cancer,
– taking medicines, for example, iodine (amidaron) compounds or hormones in the treatment of hypothyroidism,
– transient hyperthyroidism may occur in the course of thyroiditis, e.g. in Hashimoto’s thyroiditis,
– secondary hyperactivity caused by excessive secretion of TSH from the pituitary gland, e.g. by a pituitary tumor.
The most common cause of hyperthyroidism is Graves’ disease, which has an autoimmune background. This means that the body produces autoantibodies against the receptor for TSH (TRAb) that „mimic” the effects of TSH, stimulating the thyroid receptors to increase the secretion of hormones T3 and T4. Consequently, the secretion of TSH by the pituitary gland is inhibited. The cause of the disease is not entirely clear. It is suspected that this is the impact of both genetic and environmental factors (smoking, stress, estrogen, infection). In the course of Graves’ disease, other autoantibodies against thyreoperoxidase (anti-TPO) and thyroglobulin (Tg) are also observed, however, they have less diagnostic significance. A characteristic symptom of the disease is the so-called Merserburg triad, ie stare, goiter and tachycardia.
Another common cause of hyperthyroidism is hyperthyroid goiter resulting from the hyperplasia of thyroid follicular epithelium, which secrete thyroid hormones in an autonomous manner, independent of TSH. Goals are typical for areas where iodine deficiency occurs. Iodine deficiency leads to hypertrophy of thyroid cells and increased secretion of TSH from the pituitary gland. As a result, cells become overly enlarged (hypertrophy) and there are too many (hyperplasia).
3. Hyperthyroidism – symptoms
Symptoms of hyperthyroidism are the result of increased secretion of thyroid hormones. Thyroid gland and its hormones control a number of metabolic processes such as protein, fat and carbohydrate metabolism, energy metabolism and heat production
– excessive sweating,
– hypersensitivity to heat,
– tachycardia (acceleration of heart rate),
– muscle weakness,
– weight loss,
– shortness of breath,
– increased appetite,
– shaking hands,
4. What is thyroid storm?
Thyroid gland is a dangerous condition that threatens health and even life. Symptoms of a thyroid breakthrough resemble symptoms of overactivity, but are more severe. It appears in people with unrecognized or incorrectly treated hyperthyroidism. The breakthrough can be infection, serious illness, surgical operations, overdose of thyroid hormones, severe stress, pregnancy.
Symptoms of a thyroid dislocation are
– increase in thyroid hormones,
– very high fever (up to 40 ° C),
– excessive sweating and dehydration,
– excessive agitation or a reverse condition leading to coma,
– symptoms of heart failure.
Mortality in the case of thyroid crisis is 30-50%, therefore the thyroid disorder requires immediate hospitalization.
5. Thyrotoxicosis – diagnostics
Diagnosis of hyperthyroidism is based on laboratory tests of TSH level, which is currently the most sensitive indicator of thyroid dysfunctions, and fT3 and fT4.
The TSH concentration is first ordered and if it is below the reference value, then the concentration of fT3 and fT4 is ordered. The normal concentration of TSH does not exclude hyperthyroidism, because it can be observed in subclinical and secondary hyperthyroidism. Although the values of TSH in the range of reference values usually reflect normal thyroid functions, it must be borne in mind that the so-called the fT4 concentration regulation point regulating the secretion of TSH by the pituitary gland is individually variable.
Determination of fT3 concentration is used to predict relapse of Graves’ disease or suspected hyperthyroidism.
Depending on whether the hyperthyroidism is primary or secondary, the concentration of TSH may be different. In the case of primary hyperthyroidism, TSH is reduced, and in the case of secondary hyperthyroidism is increased or in the norm.
In diagnostics of hyperthyroidism, immunological tests assessing the concentration of anti-receptor antibodies to TSH (TRAb) are also useful, which allows to determine the cause of hyperthyroidism.
Other laboratory auxiliary tests that may be useful in the diagnosis of hyperthyroidism include blood count (in people with hyperactivity, anemia, decreased neutrophil counts, increased number of lymphocytes, monocytes and eosinophils may occur), lipidogram (decrease in total cholesterol and LDL, slight increase in HDL) and reduction of triglycerides), increase in alkaline phosphatase (ALT), increase in total calcium.
In patients with suspected hyperthyroidism with a morphological basis, an ultrasound examination (USG) is performed. Hyperthyroidism should be differentiated with drug conditions and phaeochromocytoma, because excess catecholamines give similar symptoms to excess thyroid hormones.
6. Hyperthyroidism – treatment
The method of treatment of hyperthyroidism depends on its cause, age of the patient, the severity of the disease and co-morbidities. Therefore, the treatment method is selected individually by the doctor.
In the treatment of hyperthyroidism is used
– antithyroid drugs (thyrostatic agents), e.g. thiamazole and propylthiouracil, which inhibit the production of thyroid hormones,
– beta blockers as adjuvant therapy, used in people with cardiovascular symptoms and hand tremors,
– treatment with radioactive iodine, treatment is not used in pregnant or breast-feeding women,
– surgical treatment (thyroidectomy) consisting in the removal of the thyroid gland, is used in people with suspected malignancy