What is hypothyroidism
L'hypothyroidism is a clinical syndrome due to an inability of the thyroid gland "H" shaped endocrine present inside our neck, to synthesize its hormones. Such hormones are called triiodothyronine (or T3) is thyroxine (T.4), are summarized starting from iodine and play numerous roles in the body's metabolism: in the event of a deficit of these molecules, these processes can be altered, slowed down or even inhibited. This pathology is termed dysthyroidism, as it is associated with a non-optimal functioning of the endocrine gland. Hypothyroidism, together with thyroid hyperfunction,hyperthyroidism, are the most frequent thyroid disorders.
The stimulation of the production of this hormone is generated from the hypothalamus, the lower-center region of the brain, which produces a factor, the TRH ("Thyrotropin releasing hormone" - thyrotropin-releasing hormone), which induces the anterior portion of the pituitary - adenohypophysis - to release a second element produced by the anterior pituitary, called TSH (or Thyroid-Stimulating Hormone), which directly stimulates the thyroid to produce its hormones and to bind them to thyroglobulin, a storage protein found within the thyroid follicles.
Many can be the causes that lead to a malfunction of the thyroid gland and an insufficient production of hormones. Among the dozens of possibilities, the most important are:
- Autoimmune Diseases. The production of reactive antibodies against thyroid hormone-producing cells (including thyroid anti-peroxidase or TPO, antibodies to thyroglobulin and TSH receptor antibodies) is the mechanism by which this group of diseases are established. More frequent in women over 60, their onset can be sudden or very slow. Causes of autoimmune hypothyroidism include Thyroiditis of Hashimoto, the Graves' diseaseGraves and atrophic thyroiditis;
- Removal thyroid surgery (or "Thyroidectomy"). There are diseases, mainly neoplastic, which, for a correct therapeutic management, require the removal of the damaged part of the gland or of the whole thyroid. Complete removal is associated with permanent hypothyroidism, as there are no other sites of production of these organs;
- Radiation. It is another type of treatment for serious diseases, mainly neoplastic, at the thyroid level and in other sites, such as the brain. Prolonged use of radioactive iodine can lead to thyroid problems of varying severity, up to a destruction of the gland which, if consistent, will cause hypothyroidism;
- Alterations congenital. During the development of the fetus, it is possible that there are anatomical alterations of the thyroid (as it may not form, partially form or be in a different location from the usual one) or functional, such as the production of not fully functional hormones. In some cases, these variants do not allow a correct functioning of the gland, with thyroid problems that can reach a condition of congenital hypothyroidism;
- Infections of the thyroid, by bacteria and viruses.
- Some drugs, like amiodarone and lithium, they prevent the gland from producing its hormones normally. Chronic use of these aids is associated with a condition of hypothyroidism;
- Ingestion not consonant with iodine through diet. If your iodine intake is too much or too little compared to normal, you may have hypothyroidism.
We have seen how the causes can be numerous and very different from each other. Each of them will have a different diagnosis and treatment methodology from the others. For this reason, it was considered necessary to create classifications that would bring together all the possible causes of this pathological condition. To date, primary, secondary, tertiary or generalized resistance to thyroid hormones hypothyroidism are recognized.
This category includes all the causes that directly affect the thyroid. They are distinguished:
- Causes of congenital hypothyroidism (less frequent), such as anatomo-functional alterations, altered iodine levels during pregnancy, passage of autoantibodies through the placenta, which cause neonatal hypothyroidism;
- Causes of acquired hypothyroidism (much more frequent), such as autoimmune diseases, surgical removals (post thyroidectomy), radiotherapy, reduced or increased iodine intake with the diet, use of toxic drugs for the thyroid, neoplasms, infiltrative diseases (such as thyroiditis of Riedel) and transitory situations (thyroiditis in pregnancy, postpartum thyroiditis or post-pharmacological treatments).
Together with the tertiary, they account for less than 1% of the causes of hypothyroidism. It is due to a reduction in pituitary TSH combined with high TRH values. All the causes that lead to damage to this organ (tumors, adenomas, vascular lesions, etc.) can lead to a reduced secretion of this factor (and also of other hormones at the same time) and therefore consequently to a condition of hypothyroidism.
Type of hypothyroidism caused by the reduction of hypothalamic TRH, which induces a low stimulation of a well-functioning thyroid. They are very rare causes of hypothyroidism, most often linked to severe lesions of the central nervous system.
Hypothyroidism due to generalized resistance to thyroid hormones
Rare cause of hypothyroidism, more often of mild severity and hereditary nature (80% of cases). It is characterized by poor or absent tissue response as opposed to elevated thyroid hormone values.
The symptomatology of hypothyroidism is not always evident: it often happens that the initial symptoms of the disease are few, absent, or gradual over time, even over several years. For this reason, doctors usually distinguish two conditions of hypothyroidism from a clinical-laboratory point of view:
- Subclinical hypothyroidism (or latent hypothyroidism): characterized by a high dosage of TSH and normal levels of triiodothyronine and free thyroxine (called fT3 and fT4). Symptoms of subclinical hypothyroidism are faded or even absent. The prevalence is 4-10% in the general population and 7-26% in the elderly population;
- Manifest hypothyroidism: characterized by a high concentration of TSH compared to a low concentration of thyroxine and free triiodothyronine (fT3 low and fT4 bass). In this situation we can see clear signs and symptoms of hypothyroidism with high TSH and low thyroid hormones.
Between consequences is symptoms of a hypothyroidism overt untreated we find:
- Increase of weight
- Poor appetite
- Myxedema, thickening of the connective tissue of the dermis due to the accumulation of hydrophilic mucopolysaccharides in the cellular matrix, which induce a strong retention of liquids. Pretibial myxedema is one of the most frequent sites of formation of this problem, even if more frequent in pathologies causing hyperthyroidism, such as Graves' disease;
- On the face, myxedema produces a characteristic face, called "Myxedematous facies", consisting of: short and wide face; yellowish-gray skin; puffy, small and narrowed eyes; widened nose; tongue of increased size (macroglossia) and a tendency to face inexpressiveness;
- Fatigue and increased fatigue, with a feeling of shortness of breath even for minimal efforts;
- Reduction of the frequency (bradycardia) and cardiac contractility (which would explain less resistance to exercise);
- Intolerance to the cold;
- Dry skin
- Fragility of hair is nails;
- Hoarse voice;
- Slowdown of thoughts is movements;
- Ache is muscle weakness (cramps), including in the respiratory muscles (would explain reduced resistance to exercise and shortness of breath);
- Problems of memory (especially in the elderly population);
- Reduction of the sexual desire;
- Irregular menstruation and / or abundant, with reduced fertility and frequent hyperprolactinaemia;
- Tingling to hands and fingers;
Congenital hypothyroidism, on the other hand, is shown in newborns with excessive sleepiness, cold and dry skin, myxedematous facies (later), rare crying and screaming, slow sucking, difficulty in breathing, delayed statural and mental development (defined "cretinism" ).
Among the possible complications of this condition we can find:
- Goiter, or an increase in the volume of the thyroid gland, which takes on a hard consistency and which can cause swallowing or breathing problems;
- Increase of cholesterol circulating (hypercholesterolemia) and, consequently, of the cardiovascular risk;
- Alterations of the pregnancy, which start from a simple reduction in fertility to severe forms of pre-eclampsia. What all these conditions have in common is the increased risk of miscarriage if this condition is not diagnosed and treated;
- Myxedematous coma (most severe of all), characterized by poor thyroid activity, marked hypothermia, shaking chills, confusion and altered mental status, low heart rate and respiratory depression. Mortality from this condition is around 35-40% of patients
The therapy of hypothyroidism is generally of a medical nature and is aimed at restoring the normal state of thyroid hormone levels (a condition that is defined "Euthyroidism"). First of all, it will be important to understand the cause of this condition, as not all conditions need therapy. Transient hypothyroidism or subacute thyroiditis, for example, are treated by watchful waiting and frequent checks, in order to wait for the remission of the underlying disease and to evaluate the initiation of corrective hormone therapy.
There medical therapy it is almost exclusively based on the administration of artificial thyroxine (levothyroxine, whose drug has commercial names such as "Eutirox" or "Tirosint"), starting from low doses and increasing them until reaching a maintenance dose of the treatment that allows the correct performance of all metabolic functions of our body (especially in the case of hypothyroidism pregnant). We must avoid overdosing this drug, as this inevitably leads to a condition of pharmacological hyperthyroidism, with all the symptoms related to it (tachycardia, weight loss, nervousness, mood swings, changes in blood pressure, tremors).
There are also drugs that have both thyroxine and triiodothyronine, but they are little used as the effects they determine in the body are comparable to those obtained by administering thyroxine alone. In the case of autoimmune diseases (as for example in Hashimoto's hypothyroidism), cortisone and immunomodulatory drugs must be administered to control the underlying disease.
There surgical therapy, instead, it is used not so much to solve the hypothyroid condition, but to eliminate any pathologies that may endanger the patient (thyroid tumors, goiters, etc.). If removal is complete, replacement medical treatment with thyroxine appears to be necessary.
The therapy of myxedematous coma, a fearful complication of this condition, is a mixture of hormone replacement therapy, treatment of symptoms due to coma and concomitant diseases, such as infections.
Hypothyroidism and diet
The diet must have the correct quantities of iodine for the correct functioning of the thyroid gland: an iodine intake of less than 100 µg / day (which is defined as a "dietary iodine deficiency") in the long run can cause the onset of hypothyroidism. About two billion people in the world, mostly concentrated in mountain areas, in Europe and Africa, do not take the correct amount of iodine.
What to eat in course of hypothyroidism? The foods richest in iodine, the best natural remedies for this pathology, are seaweed, fish, shellfish and fruits and vegetables such as tomatoes, coconut, apples, mangoes and pineapples. However, it has been seen that encouraging the consumption of these foods did not significantly reduce the percentage of endemic hypothyroidism. Under the supervision of the WHO, the progressive iodization of table salt in the diet for hypothyroidism was promoted, which dramatically reduced the overall number of hypothyroid glands. In recent years, however, the great prevalence of hypertension, especially in the first world, has led to a reduction in the consumption of salt and, consequently, again to a reduced general intake of iodine in the diet.
Among the foods to be avoided, however, we find soy and its derivatives (seitan), raw broccoli, dairy products and derivatives and poor quality foods (refined carbohydrates, seed oils, margarine).Tags: Endocrinology Thyroid