O TSH may be low in several situations; primarily in hyperthyroidism or by excessive / inappropriate use of exogenous thyroid hormone (for example, in the treatment of hypothyroidism at a dose higher than that required for disease control). It may also decrease with the use of glucocorticoids, levodopa or dopamine, as well as stress, or more rarely when the gland that produces the hormone (pituitary) or hypothalamus, which produces TRH (which stimulates pituitary TSH synthesis), does not work (secondary or tertiary hypothyroidism, respectively).
On the other hand, TSH may be increased primarily in primary hypothyroidism, but also with the use of lithium, methimazole, propylthiouracil or radiographic contrasts.
The TSH test is the dosage of a hormone produced by the pituitary gland (anterior), known as Hormonium tI will gostimulant As its name says, it acts on the thyroid gland stimulating it to produce the hormones T3 (triiodothyronine) and T4 (thyroxine). TSH secretion is inhibited by increased T3 and T4 levels (negative feedback) and is stimulated by the production of TRH (thyrotropin-releasing hormone) in the hypothalamus.
It is a useful test in the evaluation of thyroid function, being considered, in isolation, the most sensitive test for the diagnosis of primary hypothyroidism.
The reference values may vary depending on the method and reagent used, therefore, these values should be clearly stated in the results reports of laboratory tests:
Premature (28 to 36 weeks): 0.7 to 27 mIU / L
Up to 4 days: 1.0 to 39.0 mIU / L
2 to 20 weeks: 1.7 to 9.1 mIU / L
21 weeks to 20 years: 0.7 to 6.4 mIU / L
21 to 54 years: 0.4 to 4.2 mIU / L
55 to 87 years: 0.5 to 8.9 mIU / L
The interpretation of the results of the examination should be performed by the doctor who requested it, together with the history and clinical examination. For more information, see a general practitioner or endocrinologist.
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