Euthyroid Sick Syndromes, also known as Non-thyroidal Illness Syndrome (NTIS), is a medical term used to describe a group of abnormalities that occur in the hormone levels of individuals who are acutely or critically ill, but whose thyroid gland is functioning normally. The word "euthyroid" refers to a normal functioning thyroid gland, while "sick syndromes" indicates the presence of an illness or disease.
In these conditions, the body's response to an acute illness or stressor leads to alterations in the production, metabolism, and regulation of thyroid hormones. Euthyroid Sick Syndromes are often characterized by changes in levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and triiodothyronine (T3). These changes typically include low T3 levels, normal or low FT4 levels, and either normal or low TSH levels.
The exact cause of Euthyroid Sick Syndromes is still not fully understood, and it can occur in a variety of medical conditions such as sepsis, trauma, heart failure, and severe burns. However, it is believed to be a physiological response aimed at conserving energy and resources during times of stress or illness.
It is important to note that the thyroid hormone imbalances observed in Euthyroid Sick Syndromes are generally transient and resolve as the underlying illness or stressor is treated. As a result, treatment for Euthyroid Sick Syndromes primarily focuses on managing the underlying condition rather than directly targeting the thyroid hormone imbalance itself.
