Thyroid Panel
Thyroid testing should distinguish function from cause. TSH and free T4 are commonly central to assessment; T3 and thyroid antibodies may answer additional questions in selected situations. The right panel is based on the clinical question, not the largest available list.
TSH and free T4
TSH reflects the pituitary signal to the thyroid; free T4 helps assess circulating hormone. A clinician interprets the pair with symptoms, medication, pregnancy status and relevant history. Results after acute illness or a recent medication change may need different interpretation.
T3, antibodies and reverse T3
T3 is often more helpful in evaluating hyperthyroidism than diagnosing hypothyroidism. TPO or thyroglobulin antibodies may support evaluation of autoimmune thyroid disease; TSH-receptor antibodies address different questions. Reverse T3 is not routinely useful for diagnosing hypothyroidism or guiding replacement treatment in otherwise healthy outpatients. Availability does not establish clinical necessity.
Preparation and follow-up
Provide a complete medicine and supplement list, including biotin. Ask the ordering clinician whether fasting, dose timing or a temporary supplement pause is necessary for your specific test. Do not independently stop medication. Discuss what each proposed test would change, costs and who will explain the results.
What different tests can and cannot answer
| Clinical question | Possible starting point | Important limitation |
|---|---|---|
| Is thyroid function abnormal? | TSH, with free T4 as appropriate | Interpretation depends on context, medicines and pregnancy. |
| Is autoimmunity involved? | Selected thyroid antibody tests | Positive antibodies do not establish the degree of hormone deficiency. |
| Is there a structural lump? | Examination and ultrasound, with specialist assessment | Normal hormone tests do not exclude an important nodule. |
| Does a food cause allergy? | Reaction history and appropriately selected allergist testing | A food IgG panel cannot diagnose or exclude allergy. |
| Are stress symptoms an adrenal disease? | Medical history and validated testing when indicated | “Adrenal fatigue” is not an established diagnosis. |
Questions and answers
What should I know about tsh and free t4?
TSH reflects the pituitary signal to the thyroid; free T4 helps assess circulating hormone. A clinician interprets the pair with symptoms, medication, pregnancy status and relevant history. Results after acute illness or a recent medication change may need different interpretation.
What should I know about preparation and follow-up?
Provide a complete medicine and supplement list, including biotin. Ask the ordering clinician whether fasting, dose timing or a temporary supplement pause is necessary for your specific test. Do not independently stop medication. Discuss what each proposed test would change, costs and who will explain the results.
Sources and further reading
- American Thyroid Association: Thyroid hormone treatment
- American Thyroid Association: Hashimoto’s thyroiditis
- NIDDK: Thyroid tests
- American Thyroid Association: Thyroid function tests
- NIDDK: Hashimoto’s disease
- NIDDK: Graves’ disease
- American Thyroid Association: Thyroid nodules
- Endocrine Society: Adrenal fatigue
- AAAAI: Limits of food IgG panel testing
- NIDDK: Diagnosis of celiac disease
- American Thyroid Association: Hypothyroidism during pregnancy
Educational information only, not medical advice, diagnosis or a treatment plan. Do not stop, start or change prescribed medication based on this resource. Pregnancy, children, significant heart symptoms and complex endocrine disease require appropriate medical care. Seek emergency help for chest pain, severe breathing difficulty, fainting, or high fever with confusion and a very fast heartbeat. A discovery call is not urgent medical care.