TSH (Thyroid-Stimulating Hormone)
Thyroid stimulating hormone, or TSH, is a type of peptide hormone made and secreted by the thyrotrope cells of the pituitary gland. This hormone is responsible for regulating the thyroid's production of thyroxine, or T4, which controls metabolism, as well as triiodothyronine, or T3, which controls the growth rate, body temperature and heart rate. Excessively low or high levels of TSH have have significant effects on growth, energy levels, weight gain and many other aspects of the body.
A TSH test is most appropriate for patients who suspect they may have a thyroid disorder, or those patients who have already been diagnosed with hypo or hyperthyroidism and who need to monitor their treatment programs. Screening may occur in adults, children or even newborns, but is most common for people who have sudden weight and energy fluctuations accompanied by mood disorders like depression or anxiety.
Normal test results range between 0.4 and 3.0 micro international units per milliliter, but some labs accept ranges as high as 4.5 or as low as 2.5. TSH concentrations above 4.5 micro IU/mL could indicate hypothyroidism, while very high levels indicate under production of thyroid hormones. If tests show that TSH levels are high, with normal T3 and T4 levels, the subject may have mild hypothyroidism. High TSH levels with low T4 levels and low to normal T3 levels indicate a more severe problem. If TSH levels are low and T3 and T4 levels are normal to high, the patient may have hypothyroidism, while low TSH with low T3 and T4 indicates non-thyroidal illness or pituitary hypothyroidism.
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