Primary, secondary, and tertiary hypothyroidism - each has different causes and symptoms. Most often, we are dealing with primary hypothyroidism, resulting from damage to the thyroid gland, which is characterized by an increased level of thyroid stimulating hormone (TSH). However, secondary (depending on the impaired function of the anterior pituitary gland) and tertiary (depending on the impaired function of the hypothalamus), characterized by a reduced or normal level of TSH, are rare.

Primary hypothyroidism: causes

Primaryhypothyroidismis caused by gland damage, which could have been caused by:

  • thyroiditis caused by autoimmune factors: Hashimoto's disease (chronic lymphocytic thyroiditis), subacute inflammation, postpartum inflammation, silent, painless inflammation, these diseases arise on an autoimmune basis;
  • total or partial thyroidectomy, with an autoimmune process, when the body's immune cells begin to attack the fragments of the thyroid gland left after surgery;
  • treatment with radioactive iodine (iodine 131I) in capsules, used, inter alia, in hyperthyroidism - this late effect occurs unfortunately in as many as 80 percent of patients;
  • irradiation that occurs during the treatment of various cancers (e.g. lymphoma or breast cancer);
  • excessive consumption of iodides, which in high concentrations inhibit the action of other hormones;
  • significant iodine deficiency in the environment;
  • congenital hypothyroidism in children born to mothers who suffered from decompensated hypothyroidism during pregnancy;
  • overdose of antithyroid drugs - hypothyroidism caused in this way usually resolves after treatment ends
  • some medications, e.g. lithium s alts, interferon, sulfonamides

Secondary Hypothyroidism: Causes

Secondary hypothyroidism is most often caused by a TSH deficiency, associated with hypopituitarism, which may be caused by a tumor, trauma or hemorrhage. The clinical symptoms of secondary hypothyroidism are similar to those of primary hypothyroidism. However, when the cause ispituitary tumor, symptoms may not be typical. This form of hypothyroidism in hormonal tests gives a low or normal concentration of TSH and a low concentration of fT4 and fT3.

Tertiary hypothyroidism: causes

Tertiary hypothyroidism is rare and is most often caused by hypothalamic tumors, sarcoidosis, or conditions that lead to a break in the continuity of the pituitary gland. This form of hypothyroidism is due to a deficiency of thyreoliberin (TRH) and is characterized by a reduced or normal level of TSH.

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