The test strips you want to refer to here would be pregnancy test strips, and thyroid disorders do not usually cause false positives on test strips. Pregnancy test strips measure the value of human chorionic gonadotropin in the body to detect pregnancy. Human chorionic gonadotropin is a specific hormone in the body that occurs after pregnancy, whereas thyroid disorders are caused by abnormal thyroid function and do not affect human chorionic gonadotropin. If a test strip gives a false positive in the absence of pregnancy, it may be due to the quality of the test strip or it may be due to prolonged placement in urine. False positives may also occur if the test strip has been exposed to high temperatures for a long period of time. If the patient is not sure if she is not pregnant, it is recommended to go to the hospital and take a blood HCG test under the guidance of a doctor to determine if she is pregnant, as blood HCG tests are usually more accurate.