Low T 3 / Low T4 Syndrome

The low T3 / low T4 syndrome corresponds to decreased serum levels of thyroid hormones in clinically euthyroid patients with systemic diseases unrelated to the thyroid. Diagnosis is made by exclusion of hypothyroidism. The underlying disease must be treated; Thyroid hormone replacement is not indicated.

The low T3 / low T4 syndrome corresponds to decreased serum levels of thyroid hormones in clinically euthyroid patients with systemic diseases unrelated to the thyroid. Diagnosis is made by exclusion of hypothyroidism. The underlying disease must be treated; Thyroid hormone replacement is not indicated.

(See illustration of the thyroid function.) The low-T3 / low T4 syndrome corresponds to decreased serum levels of thyroid hormones in clinically euthyroid patients with systemic diseases unrelated to the thyroid. Diagnosis is made by exclusion of hypothyroidism. The underlying disease must be treated; Thyroid hormone replacement is not indicated. Patients with various acute or chronic diseases, thyroid independent may have pathological test results of thyroid function. These include acute and chronic diseases, particularly hungry states, protein deficiency, severe trauma, myocardial infarction, chronic renal failure, diabetic ketoacidosis, anorexia nervosa, cirrhosis, burns, hypothermia undSepsis. Decreased triiodothyronine (T3) levels are the most common. Patients with more severe or prolonged illness also show decreased thyroxine (T4) levels. Serum levels of the reverse T3 (rT3) are elevated. The patients are clinically euthyroid and do not have elevated thyroid stimulating hormone (TSH) levels. The pathogenesis is not known, but may be associated with a reduced peripheral conversion of T4 to T3, a reduced degradation of from T4 nascent rT3 as well as a decreased thyroid hormone binding to thyroxine-binding globulin (TBG). Pro-inflammatory cytokines (eg. As tumor necrosis factor-alpha, IL-1) may be responsible for some changes. The interpretation of abnormal thyroid function tests in seriously ill patients is complicated by effects of many drugs. These include iodinated contrast agent, and amiodarone, the effect on peripheral T4 / T3 -Konversion, and drugs such as dopamine, and corticosteroids, which inhibit pituitary TSH secretion so that serum TSH levels to fall and T4 secretion decreases below. Tips and risks thyroid function tests should not be performed in patients in intensive care, unless there is an increased suspicion of a thyroid malfunction. Diagnostic TSH serum cortisol Clinical judgment The diagnostic difficulty is the distinction between hypothyroidism and a low-T3 / low T4 syndrome. The best test of this is the measurement of TSH, which may be low, normal or slightly increased in low-T3 / low T4 syndrome, but not as high as is the case with hypothyroidism. The serum rT3 is increased, this measurement has found no place in the routine. may be increased cortisol serum in low-T3 / low T4 syndrome, while it is in hypothyroidism lowered by the pituitary / hypothalamus disorder or low-normal. Since the clinical presentation and diagnosis are nonspecific, it requires the clinical picture to interpret the pathological thyroid tests in acutely or chronically ill. Unless a thyroid dysfunction is suspected thyroid values ??for patients in the ICU should be determined only orienting. Therapy Treatment of the underlying disease, the treatment by substitution of thyroid hormones is not appropriate. If the underlying condition is treated, the results of thyroid tests normalize. Conclusion Many seriously ill patients have low thyroid hormone levels but are not clinically hypothyroid and require no additional thyroid hormone. Patients with low T3 / low T4 syndrome have low, normal or only slightly elevated TSH levels, in contrast to the significant increase in TSH real hypothyroidism.

Health Life Media Team

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