The decrease in the production and adequate release of thyroid hormones can cause a series of symptoms, in the context of a pathology called hypothyroidism.
Concepts about hypothyroidism
As we already know, thyroid hormones (so-called free triiodothyronine and free thyroxine, free T3 and free T4, respectively) are essential for the functioning of various organs. Therefore, the decrease of its circulating levels below normal limits, causes dysfunction in various apparatus and systems, including neurons and the heart.
Hypothyroidism is defined as a decrease in blood levels of free T4, in conjunction with an increase in the level of thyroid stimulating hormone (TSH). In some cases, TSH may be elevated without affecting circulating free T4 levels, calling this condition sub-clinical hypothyroidism.
Causes of hypothyroidism
For the synthesis of thyroid hormones, adequate production of thyrotropin-releasing hormone (or TRH, which is generated in the hypothalamus), of TSH (which is produced in the pituitary) and the proper functioning of the thyroid gland is required.
In central hypothyroidism (due to the presence of tumors, ischemia, postpartum necrosis, among others) the pituitary gland (secondary hypothyroidism) or the hypothalamus (tertiary hypothyroidism) are affected.
However, most hypothyroidisms are primary (in 95% of cases) associated with involvement of the thyroid gland. Its causes include: iodine deficiency goiter, autoimmune causes such as Hashimoto's thyroiditis (produced by antibodies that attack the thyroid), thyroidectomy (surgical procedure indicated for the treatment of some types of hyperthyroidism), radiation, congenital hypothyroidism, drug-induced hypothyroidism, among others.
How is hypothyroidism diagnosed?
The diagnosis of hypothyroidism is based on laboratory results, associated with the symptoms reported by the patient. However, hypothyroidism is a highly variable disease and some patients may have decreased T4 levels and no symptoms. Some symptoms reported by patients are:
· Weight gain.
· Sleep disorders.
· Presence of thyroid goiter (diffuse enlargement of the thyroid gland).
· Edema or swelling in the face.
· Fatigue or tiredness
· Cold intolerance
· Dry skin.
· Menstrual disturbances
· Mild joint pain.
· Bradycardia (decrease in heart rate below normal values).
· Slow speech and course of thought.
Associated with the symptoms, laboratory tests should be performed, in the first instance serum TSH levels should be requested. If these are elevated, free T4 levels should be requested. These two measurements are obtained from a blood sample, in the morning hours, during the fasting of the patient. If the results show an elevated TSH and a decreased free T4, it is suggested to repeat them to corroborate the diagnosis of hypothyroidism.
Given this diagnosis, other laboratory tests should be requested to determine the exact cause of its production and where the original fault is found (in the thyroid, pituitary or hypothalamus). In the event that autoimmune disease is suspected, levels of anti-thyroid antibodies (such as anti-peroxidase or Anti-TPO antibodies) are requested.
It will also be necessary to perform a thyroid ultrasound and in cases in which pathology of the pituitary or hypothalamus is suspected, neuroimaging studies such as a brain MRI will be requested. Other studies requested in sub-clinical hypothyroidism will be the complete hematology and the lipid profile.
What is the proper treatment for hypothyroidism?
In most cases, hypothyroidism is a chronic and permanent condition that requires ongoing treatment. Treatment is based on the supplement of thyroid hormones with synthetic levothyroxine (T4) administered orally, in the morning hours and during the fasting of the patient, on a daily and continuous basis.
Synthetic levothyroxine is prescribed in micrograms, so its doses must be taken exactly and uninterruptedly, since a small change could condition the continuity of the symptoms of hypothyroidism or, on the contrary, produce symptoms of hyperthyroidism due to excess of the required dose.
The main goal of treatment is to normalize TSH levels, in addition to decreasing the size of the goiter (if present), reducing symptoms, and preventing complications of severe hypothyroidism.
When treatment is started, TSH and free T4 levels should be monitored to avoid exceeding the required levels of thyroid hormones. In elderly patients with cardiovascular comorbidities, low doses of levothyroxine should be started and gradually increased, if necessary, according to the monitoring of symptoms and hormone levels.
It is important that the patient with hypothyroidism constantly go to the doctor so that their treatment is monitored and controlled in the best possible way.
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