Causes of high levels of thyroid-stimulating hormone include hypothyroidism, a tumor in the pituitary gland, or a need to increase the amount of thyroid hormone medicine, according to WebMD. The pituitary gland produces TSH, which then stimulates the thyroid to produce other hormones to regulate metabolism.
Hypothyroidism is a condition where the thyroid gland does not produce a sufficient amount of hormones for the body. It is most common in females over age 60, according to Mayo Clinic. In its early stages, hyperthyroidism may not cause any symptoms; however, as it advances, it can result in weight gain, pain, infertility and heart diseases. The THS level is a common blood test for hyperthyroidism.
Prior to the development of the THS test, detecting hypothyroidism was difficult and doctors were unable to diagnose the condition until it advanced to cause other symptoms. Because the test is the best screening tool available, doctors order it first and follow up with the thyroid hormone test if the THS levels are high, reports Mayo Clinic.
Medical care providers also use the THS test in monitoring patients who use thyroid replacement therapy. The test results are useful for doctors as they determine the initial dosage for the patient and in determining if there is a need to make adjustments over time, indicates Mayo Clinic.