About TSH / Thyroid stimulating hormone:
Thyroid stimulating hormone, often abbreviated to TSH and sometimes called thyrotropin or thyrotropic hormone, is a pituitary hormone that can be used to stimulate the thyroid gland and encourage production of thyroxine and triiodothyronine. This has been shown to stimulate the metabolism of almost every tissue in the body.
TSH concentrations tend to be higher in children than they are in adults. They gradually drop in younger children and decrease further during puberty and into adulthood.
TSH Mechanism & Function
Disease diagnostics are one of the main functions of thyroid stimulating hormone. TSH concentrations are measured to determine whether patients have too many thyroid hormones (hyperthyroidism) or too few thyroid hormones (hypothyroidism). The levels of TSH and T4 are calculated to give a diagnosis. In some patients, measuring T3 levels can give more information.
The target range of TSH level for patients undergoing treatment ranges between 0.3 and 3.0 μIU/mL. Measurement of TSH alone is usually adequate for hypothyroid patients that are taking thyroxine. An increase in TSH above the normal range shows a lack of effectiveness in the treatment while a noticeable reduction in TSH suggests over-treatment. Changes to the dosage can help in both of these cases.
However, there are some issues with the interpretation of TSH measurement, which may cause misdiagnosis. The same TSH concentration can suggest different things when used for diagnosis of thyroid dysfunction or for monitoring of substitution therapy with levothyroxine. This is usually because the TSH-T3 shunt is disrupted in treated hypothyroidism, causing the shape of the relation between free T4 and TSH concentration to be altered.