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Excess amounts of T3 circulate in the bloodstream. It is unclear if this is a consequence of compensatory hyperdeiodination or if it results from impaired uptake by certain cell types. Increased T3 levels in the blood may be toxic to some organs and contribute to the signs and symptoms of Allan–Herndon–Dudley syndrome. [citation needed]
Myxedema coma is an extreme or decompensated form of hypothyroidism and while uncommon, is potentially lethal. [ 1][ 2][ 3] A person may have laboratory values identical to a "normal" hypothyroid state, but a stressful event (such as an infection, myocardial infarction, or stroke) precipitates the myxedema coma state, usually in the elderly.
Euthyroid sick syndrome ( ESS) is a state of adaptation or dysregulation of thyrotropic feedback control [ 1] wherein the levels of T3 and/or T4 are abnormal, but the thyroid gland does not appear to be dysfunctional. This condition may result from allostatic responses of hypothalamus-pituitary-thyroid feedback control, dyshomeostatic disorders ...
The main diagnostic sign is an oral body temperature that averages well below 37.0 °C (98.6 °F). This overlaps with normal body temperature, which is usually within the range of 36.5–37.5 °C (97.7–99.5 °F). [5] [6] Wilson says that his diagnosis is confirmed if the patient responds to treatment with slow-release T3 (SR-T3).
Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. [ 3] Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. [ 3] Some, however, use the terms interchangeably. [ 5]
In any case, the concentration of T 3 in the human blood plasma is about one-fortieth that of T 4. The half-life of T 3 is about 2.5 days. [3] The half-life of T 4 is about 6.5 days. [4] T 3 levels start to rise 45 minutes after administration and peak at about 2.5 hours.
An elevation in thyroid hormone levels is suggestive of thyroid storm when accompanied by signs of severe hyperthyroidism but is not diagnostic as it may also correlate with uncomplicated hyperthyroidism. [15] [18] Moreover, serum T3 may be normal in critically ill patients due to decreased conversion of T4 to T3. [15]
Low-T3 syndrome and high-T3 syndrome: Consequences of step-up hypodeiodination, e.g. in critical illness as an example for type 1 allostasis, [20] or hyperdeiodination, as in type 2 allostasis, including posttraumatic stress disorder. [12] Resistance to thyroid hormone: Feedback loop interrupted on the level of pituitary thyroid hormone receptors.