Thyroid TSH Function Test

Thyroid-stimulating hormone (TSH) is measured in the blood to help evaluate thyroid function.

About the thyroid

The thyroid is a butterfly-shaped gland in the front of the neck that helps regulate how your body uses energy. It plays a role in many essential processes, including metabolism, heart rate, body temperature, and nervous system function. Thyroid activity is regulated by the pituitary gland, which produces thyroid-stimulating hormone (TSH). TSH signals the thyroid to produce thyroid hormones—primarily T4. When this system is out of balance, it can lead to thyroid disorders that affect many parts of the body. While untreated thyroid disease can increase the risk of complications, most thyroid conditions can be effectively managed with medication and regular monitoring.

Thyroid-stimulating hormone (TSH)

TSH helps control how much thyroid hormone your body produces.

• High TSH levels may indicate an underactive thyroid (hypothyroidism)
• Low TSH levels may indicate an overactive thyroid (hyperthyroidism)

TSH is often the first marker used to assess thyroid function and is commonly tracked over time in people with known thyroid conditions. If test results identify abnormal TSH levels, free thyroxine (T4) blood levels will be tested using your submitted sample at no additional cost to you to provide information needed to help your healthcare provider diagnose hypothyroidism.

Symptoms of thyroid disorders can be mild, moderate, or severe and often resemble other medical conditions. You may consider getting a thyroid function test if you're experiencing the following symptoms:

Hypothyroidism (underactive thyroid) symptoms can include:

• Weight gain
• Fatigue
• Increased sensitivity to cold
• Thinning hair
• Enlarged thyroid gland (goiter)
• Muscle aches and pains
• Joint pain and stiffness
• Elevated cholesterol levels
• Constipation
• Depression
• Problems with memory
• Slower than normal heart rate
• Dry skin
• Muscle weakness
• Facial puffiness
• Hoarseness

Hyperthyroid (overactive thyroid) symptoms can include:

• Increased appetite
• Irregular heartbeat
• Palpitations—a fluttering or pounding heartbeat
• Unintentional weight loss
• More frequent bowel movements
• Anxiety or nervousness
• Sweating

Purchaser: You must be 18 years of age or older to purchase a test on questhealth.com.

Patient: This test can be performed on patients between 10 and 100 years old. If this test will be performed on someone less than 18 years old:

• The appropriate age bracket needs to be selected during purchase
• Both parent/guardian (hereinafter "parent") and patient information will need to be provided during test registration
• Both parent and patient must be present for sample collection, the parent will need to have their identification available at collection
• Results will be provided to the listed parent

Sample collection: This test requires sample collection at a Quest Diagnostics location or through Quest Mobile® where available, a convenient option for in-home sample collection*. Collection is not available in AZ or HI.

*Check your zip code here for service availability, testing may not be available in all locations. Quest Mobile is currently only available for individuals ages 18+.

Please note: Laboratory testing for children under 18 years of age should always be conducted with the guidance of a qualified healthcare provider. Our tests are designed to support continuity of care, ease of access, and empower families with accessible health information. They are not a substitute for medical evaluation or ongoing care from a pediatrician. Parents should review test results with their child's healthcare provider to ensure appropriate interpretation, follow-up, and treatment in the context of the rest of your child's care. If your child is experiencing symptoms or you have concerns about their health, please contact your pediatrician or seek other medical care immediately.

After you provide your specimen, it generally takes few business days to process and release your test results. However, processing times may vary. Your test results will be available in a clear and easy-to-read report. If you have or create a MyQuest® account, you may be able to review your new results there with your other Quest results. If your results differ from expected ranges, you may receive an alert call from an independent healthcare coordinator. Independent healthcare providers are available to discuss questions or concerns you may have regarding your results and may be able to prescribe treatment.

If this test is performed on someone less than 18 years old, the results will be provided to the registered parent.