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Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T 4), and then triiodothyronine (T 3) which stimulates the metabolism of almost every tissue in the body. [1]
The syndrome can present with variable symptoms, even between members of the same family harboring the same mutation. [1] Typically most or all tissues are resistant to thyroid hormone, so despite raised measures of serum thyroid hormone the individual may appear euthyroid (have no symptoms of over- or underactivity of the thyroid gland).
The most useful marker of thyroid gland function is serum thyroid-stimulating hormone (TSH) levels. TSH levels are determined by a classic negative feedback system in which high levels of T3 and T4 suppress the production of TSH, and low levels of T3 and T4 increase the production of TSH. TSH levels are thus often used by doctors as a screening ...
Stress suppresses TSH, [5] and alterations in thyroid hormone levels may arise in psychiatric illness. In major depressive disorder, an NTIS-like phenotype may be observed, with reduced T3 and increased rT3. T4 may be elevated, and TSH is usually normal, although TSH's normal circadian rhythm may be disrupted. [2]
Levels may be abnormal in the context of other illnesses, and TSH testing in hospitalized people is discouraged unless thyroid dysfunction is strongly suspected [8] as the cause of the acute illness. [17] An elevated TSH level indicates that the thyroid gland is not producing enough thyroid hormone, and free T 4 levels are then often obtained.
Each time the dose is adjusted, TSH levels may be measured at that frequency until the correct dose is determined. [71] Once titrated to a proper dose, TSH levels will be monitored yearly. [71] The target level for TSH is the subject of debate, with factors like age, sex, individual needs and special circumstances such as pregnancy being ...
The diagnosis of hyperthyroidism is confirmed by blood tests that show a decreased thyroid-stimulating hormone (TSH) level and elevated T 4 and T 3 levels. TSH is a hormone made by the pituitary gland in the brain that tells the thyroid gland how much hormone to make. When there is too much thyroid hormone, the TSH will be low.
TSH release in turn is stimulated by thyrotropin releasing hormone (TRH), released in a pulsatile manner from the hypothalamus. [39] The thyroid hormones provide negative feedback to the thyrotropes TSH and TRH: when the thyroid hormones are high, TSH production is suppressed. This negative feedback also occurs when levels of TSH are high ...