Non-thyroidal illnss syndrome
Various abnormalities of thyroid hormone and TSH levels can be registered as a side effect in a number of diseases. That condition is called Euthyroid Sick Syndrome (ESS). According to some estimates, in hospitalized patients, a low level of T4 occurs in approximately 20% of patients, elevated level of T4 in 5 - 15%, while low level of T3 can be detected in 25 - 70% of patients. About 10% of patients have a irregular TSH value. Nonthyroidal illness syndrome is a condition with disturbed functioning of the hypothalamus-pituitary-thyroid axis due to various external factors that are not directly related to the mentioned organs.
These are most often different acute and chronic infectious diseases, chronic non-infectious diseases (psychiatric, gastrointestinal, pulmonary, cardiovascular and renal diseases, stroke, malignant tumors, infiltrative and metabolic diseases), severe malnutrition, conditions after complicated and long-term surgical procedures and solid organs and hematopoietic stem cells of the bone marrow transplantations. Life-threatening patients and patients treated in intensive care units are also often affected (sepsis, conditions after massive trauma, burns and surgeries) and also emotional stress and taking certain medications can be triggers. Cytokine-mediated changes (IL-1, IL-6, TNF-α) occur in the hypothalamus, pituitary gland and thyroid gland, which lead to reduced stimulation of the thyroid gland, pituitary gland and hypothalamus or changes in thyroid hormone metabolism.
Clinical picture and diagnosis
The clinical picture depends on the primary disease, symptoms of reduced or increased thyroid function are not present, but as already mentioned, laboratory tests can determine different values of TSH and thyroid hormones. Usually there is a normal value of T4 and TSH, a reduced value of T3 with an increased value of rT3. In a severe form of the nonthyroidal illness syndrome, there is a decreased value of T4, T3 and TSH with an increased value of rT3. The diagnosis is based on specialist and ultrasound examination of the thyroid and laboratory determination of thyroid hormones and TSH. Specific thyroidological treatment is not necessary and the principle of action is the treatment of the underlying disease that causes a secondary disorder of the thyroid function.