The first test your doctor will usually request to detect a problem with your thyroid gland is a TSH test. If your TSH level is abnormal, the doctor will usually request a free T4 test to confirm the diagnosis. A free T3 test may be requested as well.
- TSH – to test for hypothyroidism, and hyperthyroidism, to screen newborns for hypothyroidism, and to monitor treatment with thyroid hormone tablets.
- Free T4 – to test for hypothyroidism and hyperthyroidism.
- Free T3 – to test for hyperthyroidism.
Additional tests that may be performed include:
Thyroid antibodies - to help differentiate different types of thyroiditis and identify autoimmune thyroid conditions
Calcitonin - to help detect overproduction of calcitonin
When are these lab tests requested?
Since one out of every 4,000 infants is born without a working thyroid gland, there is a UK screening programme for all newborn babies looking for hypothyroidism. This occurs approximately 1 week after birth and uses a drop of blood taken from a heel prick which is sent to the laboratory for a TSH test.
Thyroid function tests are also requested when a doctor notices that a patient has symptoms which can occur in thyroid disease. In hypothyroidism for instance a patient might show signs of fatigue, weight gain, increased sensitivity to cold, or skin dryness. In hyperthyroidism the signs might include fatigue, weight loss, increased sensitivity to heat, and nervousness. Tests are also requested in individuals who have a family history of thyroid disorders.
Non-Laboratory Tests
Ultrasound – an imaging scan that allows doctors to determine whether a nodule is solid or fluid-filled and can help measure the size of the thyroid gland
Thyroid Scans – a test that uses radioactive iodine or technetium to look for thyroid gland abnormalities and to evaluate thyroid function in different areas of the thyroid
Biopsies – often a fine-needle biopsy, a procedure that involves inserting a needle into the thyroid and removing a small amount of tissue and/or fluid from a nodule or other area that the doctor wants to examine; an ultrasound is used to guide the needle into the correct position