Blood test, thyroid stimulating hormone (TSH)

Procedure Information

What is Thyroid function test?

Thyroid blood tests are useful in determining if your thyroid gland is functioning properly or not. This is done by measuring the amount of thyroid hormone in your blood. 

Your thyroid gland is responsible for the production of thyroid hormones. Thyroid hormones travel through your bloodstream and act on many organs and regulate many aspects of your body’s metabolism including energy and weight. This is why disturbances in thyroid hormone can lead to weight loss or weight gain.

Thyroid gland diseases are diagnosed based on your symptoms and your blood test results that measure the level of TSH and the thyroid hormone thyroxine.

Why would I get a Thyroid function test?

• Diseases of the thyroid gland can manifest either as hypothyroidism (which means decreased thyroid hormone production) or hyperthyroidism (which means increased thyroid hormone production).
• Hyperthyroidism symptoms include weight loss (caused by increased metabolism), increased heartbeat, insomnia, and anxiety.

Hypothyroidism symptoms include weight gain (caused by decreased metabolism), menstrual irregularity, dry and puffy skin, and fatigue.

Many thyroid disorders can cause diseases of the thyroid. These disorders include grave’s disease, thyroid tumors, Hashimoto’s disease, thyroid nodule, goiter, and thyroid cancer. 

What happens during a Thyroid function test?

A needle is inserted and a small amount of blood is collected into a vial or syringe. Once enough blood is collected, the needle is removed and the puncture site is covered with a bandage. The procedure is painless and takes only a couple of minutes.

Thyroid blood tests include thyroid-stimulating hormone (TSH), free T3 or free triiodothyronine, and free T4 or free thyroxin. Measuring the levels of these hormones helps determine the state of your thyroid gland and whether you have hyper or hypothyroidism.

What to expect after a Thyroid function test?

There are no precautions you need to take. You should be able to drive yourself home and do all your normal activities.

The most important test is measuring the thyroid-stimulating hormone (TSH.) Thyroid hormone deficiency (hypothyroidism) leads to an elevated TSH level, while thyroid hormone excess (hyperthyroidism) leads to a low TSH level. 

If your TSH is abnormal, your doctor will ask for measurement of thyroid hormones directly, including thyroxine (T4) and triiodothyronine (T3), to further evaluate the problem.

Other things that can be measured to further assess your thyroid function include thyroid antibodies, calcitonin, and thyroglobulin.

Other things can be measured to assess your thyroid function and help in the diagnosis of many conditions include thyroid antibodies, calcitonin, and thyroglobulin.

Conclusion

Be aware that abnormal readings do not necessarily mean a thyroid disease is present, as each test can be affected by a variety of factors.

Your GP may refer you to an endocrinologist (a specialist in hormone disorders) if you are pregnant, have just given birth, younger than 16, taking medications known to cause thyroid hormone abnormalities, such as lithium or amiodarone, have another health condition, such as heart disease, which may complicate your medicine.

Citations

Cleveland Clinic: Thyroid Blood Tests

Nhs: Underactive thyroid (hypothyroidism)