What is hyperthyroidism
Hyperthyroidism is a pathological condition due to the presence of elevated levels of thyroid hormones in the blood, due to an increase in function and production by the thyroid gland. It is a more frequent pathology in women and, among the thyroid disorders, it is the one that has the greatest family correlation.
The thyroid is an organ present inside our neck, stimulated upstream by the hypothalamus, which produces a factor, the TRH, which will stimulate the pituitary gland to release a factor that will directly activate the endocrine organ , TSH (or thyrotropin). This organ basically produces two types of hormones, which control most of the metabolic processes in our body:
- Triiodothyronine (or T.3): it has 3 iodine atoms, it is the most active hormone of the two (effects 10 times higher than T.4) and constitutes 20% of thyroid secretions;
- Thyroxine (or T.4): has 4 iodine atoms, constitutes the 80% of endocrine secretions and is less effective than T3. Therefore, approximately 40% of the circulating quota is converted in the periphery into T.3, in order to have a better response to the needs of the organism.
Through the coordination of the levels of thyroid hormones, TSH and TRH, we can have a fine control of the needs of our organism, through negative feedback mechanisms: if the levels of thyroid hormones were to be low or insufficient to carry out the activities of the organism, there is a stimulation to the release of TRH and TSH, which will stimulate the gland in such a way as to be able to produce what is necessary and, vice versa, will stop its production in the event that the levels of T3 eT4 circulating are higher than the norm.
Values of hyperthyroidism
In the blood, these hormones can be bound to plasma proteins, therefore in silent form, or be free from any bond, composing that hormonal fraction that is actually active and available to the body.
In adults, the average concentration of the various components is:
- Total thyroxine (tT4): 60 - 150 nmoles / L;
- Free thyroxine (fT4): 10 - 25 pmoles / L;
- Total triiodothyronine (tT3): 1.1 - 2.6 nmoles / L;
- Free triiodothyronine (fT3): 3.0 - 8.0 pmoles / L;
- TSH: 0.15 - 3.5 mU / L.
These values may differ slightly from laboratory to laboratory, but mainly according to age and the concomitant presence of pregnancy.
Causes of hyperthyroidism
We can distinguish:
- Primary hyperthyroidism, i.e. linked to an alteration in the thyroid itself. Among the most frequent causes we remember: Basedow-Graves disease, autoimmune hyperthyroidism which, through the production of thyroid stimulating antibodies (or TSI), binds to the thyroid receptors for TSH, inducing the activation of the gland; toxic multinodular goiter, in which, due to an insufficient production of thyroid hormones over time, there is a generalized increase in the size of the gland; solitary toxic thyroid adenoma (or Plummer's disease), where the increase in size of the gland is asymmetrical, as an area of glandular tissue begins to produce thyroid hormones by freeing itself from negative feedback mechanisms; thyroiditis, divided into acute (with infectious etiology, which lead to a rapid release of thyroid hormones, which reach very high concentrations, due to the acute destruction of the glandular parenchyma, causing the so-called "thyrotoxic crisis"), subacute (with viral or autoimmune), and chronic (with a prevalent autoimmune etiology, as in the case of Hashimoto's thyroiditis; some tumors; thyroid ectopic tissue secreting active hormones;
- Secondary hyperthyroidism, that is all those causes that derive from an increased stimulation upstream of the thyroid gland (at the level of the hypothalamus and / or pituitary gland through the increased secretion of TRH and / or TSH respectively); they are lesions that have a lower frequency than the primary thyroid pathologies described above. Among the most frequent, we remember the TSH-secreting pituitary macroadenomas;
- Iatrogenic, caused by inadequate intake of artificial thyroid hormones (such as levothyroxine), which produces a condition called "factitic thyrotoxicosis" or "artificial thyrotoxicosis". In some cases, these drugs are prescribed for clinical conditions in which there is low production of these hormones (called “hypothyroidism”), or for weight loss purposes.
The symptoms depend on the increase in oxygen consumption due to the increase in metabolic processes, with a consequent increase in the production of heat linked to metabolism. Therefore, the consequences of hyperthyroidism are expressed through general manifestations and symptoms of an overfunctioning thyroid, such as:
- Restlessness and hyperactivity;
- Muscle weakness, called "asthenia";
- Fever, if there is an ongoing infectious cause;
- Excessive thirst
- Intolerance to heat and increased sweating, with warm, thin and yellowed skin due to the increase in local vascularization;
- Presence of edema in the lower limbs (as in the case of pretibial myxedema of Graves' disease);
- Sudden weight loss and fragile and thin hair, due to an increased muscle and fibrillar protein catabolism of the skin appendages.
From a cardiovascular point of view, hyperthyroid can complain of:
- Tachycardia (i.e. an increase in heart rate) and palpitations;
- Increased force of contraction of the heart (called "cardiac inotropism")
- Arterial hypertension, which, if not corrected early, can lead to left ventricular hypertrophy due to the increased effort of the heart chamber to be able to pump blood into the systemic circulation;
- Changes in the conduction of the heartbeat, including severe arrhythmias (including atrial fibrillation)
From a neurological point of view, however, we have an involvement of the brain and the central nervous system, which are affected by the alterations in the levels of circulating thyroid hormones. Patients often complain:
- Insomnia and sleep disturbances;
- Psychosis (which appears when these alterations continue over time without suitable therapy).
From the glandular point of view, it is very common to complain of a mass inside the neck, felt as bulky or heavy and which can compress the underlying structures, namely the trachea and esophagus.
In addition to all this, patients may complain of genitourinary problems (irregular menstruation, infertility, decreased libido, etc.), at the level of the eyes (exophthalmos, i.e. the protrusion of the eye beyond the eyelid line, particularly important in Graves' disease), in the intestine (nausea, vomiting, diarrhea, etc.).
In the case of hyperthyroidism in pregnancy, the presence of symptoms depends on the underlying cause: autoimmune diseases tend to improve with pregnancy (perhaps due to the state of generalized immunosuppression), while others require rigorous monitoring.
In this pathology, the diagnostic process is fundamental, as each cause has its own treatment and it is important to know right away what the path to take in order to have a faster resolution of hyperthyroidism and a better long-term result.
Initially, the suspicion must come from a clinic suggesting a thyroid disease. A thorough physical examination and a complete medical history of the patient must be proceeded immediately. In particular, it must be evaluated very well if the patient is taking specific drugs for other concomitant diseases (amiodarone, thyroid hormones for the treatment of hypothyroidism, etc.), has been exposed to pathological agents, such as bacteria and viruses, if there is familiarity with other people of the family of origin etc ...
Then, one of the first actions to take is a simple blood test to measure the thyroid hormones in the circulation. You can therefore have different paintings:
- Normal TSH levels, with normal free thyroid hormone levels: this is the picture of the healthy patient;
- Low TSH levels, with high ft4 and ft3 levels: picture of the patient with subclinical hyperthyroidism, in which there is no manifestation of hyperthyroidism, but in any case there is a situation of equilibrium;
- Very low TSH levels, with a high ft3 and ft4 level: this picture belongs to manifest hyperthyroidism, as the increase in the blood concentration of thyroid hormones is associated with a characteristic symptom set of the disease.
In addition to this, other elements can also be sought from the blood sample, useful for defining the underlying cause of hyperthyroidism. For example, the presence of autoantibodies against various thyroid structures, such as anti-thyroperoxidase antibodies, anti-thyroglobulin antibodies and anti-TSH receptor antibodies, in the event that we are inclined to an autoimmune disease; alteration of the patient's biological parameters, such as the presence of anemia, dyslipidemia, increase in inflammation indices, increase in hepatic transaminases etc…; thyroglobulin levels, as an increased blood concentration can be observed in some types of tumors, such as follicular adenocarcinoma.
Often, however, it is necessary to use precise imaging exams, in order to better view and evaluate the glandular structure. Among the examinations that can be performed, we find:
- Ultrasound of the thyroid, with echocolordoppler of the thyroid vessels. It is the first-line exam, simple to perform and very low cost. It does not require a particular preparation and allows to distinguish very well possible structural and vascularity alterations of the organ. During this procedure, it is possible to carry out further tests, such as aspiration of the contents of possible thyroid nodules, in order to evaluate the aspirate under the microscope;
- Scintigraphy of the thyroid gland, using a radiolabeled iodinated contrast medium (such as technetium 99Tc pertecnetato), so that it is picked up by the thyroid gland and allows you to view the structure of the gland from the outside
- CT and MRI are not among the most useful tests for the evaluation of the thyroid, but are used in the case in which there is an involvement of other structures within the body, as in the case of a metastasis starting from a primary thyroid tumor , especially when associated with a FDG-PET.
Treatment of hyperthyroidism
Once the cause has been found, targeted therapy is established against the agent causing the problem. Therapy can be of the following type:
- Symptomatic drugs can be used, against the systemic symptoms of the disease (NSAIDs and antibiotics, in the case of a microbiological cause; beta-blockers, such as propranolol, if persistent tachycardia appears; cortisone drugs, to lower the degree of inflammation etc ...), but also drugs aimed at solving the thyroid problem (synthetic antithyroid drugs, such as methimazole (trade name "tapazole"), which inhibit the production of thyroid hormones; iodide and radioactive iodine, which prevent the release of thyroid hormones, inducing a destruction of the glandular parenchyma);
- Percutaneous, such as drainage of abscesses and / or sacked collections of liquids, to be performed under ultrasound control;
- Surgical on the gland, ie the “thyroidectomy”, which can be lobar, subtotal or total based on the severity of the underlying disease and the percentage of parenchyma affected by the pathology. We must be very careful, as this intervention is associated with important problems, among which it is important to remember the alterations in calcium levels due to the possible removal of organs involved in calcium metabolism, called parathyroid glands.
There are also specific protocols for pregnant patients, which must be constantly monitored and treated very carefully, primarily with antithyroid drugs only in the case of overt hyperthyroidism.
Hyperthyroidism and nutrition
Lifestyle habits also need to be regulated and you need to know what to eat during hyperthyroidism: avoid smoking and alcohol, take a lot of fiber and low calories, such as fruits and vegetables in general, preferably raw, a correct amount of protein and avoid coffee, tea, smoked cheeses, spicy sauces, seafood and fatty meats and iodized salt.
Tags: Endocrinology Thyroid