How to read thyroid tests
Other platforms explain it with text and video. In VMS you practice it on the patient.
Thyroid problems cause tiredness, weight change, heart rhythm problems and mood changes. A few simple patterns explain most thyroid results.
Step by step
Start with TSH
TSH is the best first test. The pituitary raises TSH when thyroid hormone is low and lowers it when hormone is high. [1]
Add free T4
If TSH is abnormal, check free T4 to see how much active hormone is in the blood. [1]
Match the pattern
Use the table below. High TSH with low free T4 is primary hypothyroidism; low TSH with high free T4 is hyperthyroidism. [1]
Check T3 when needed
If TSH is low but free T4 is normal, check T3. Some overactive thyroids raise only T3. [1]
Think about the pituitary
Low TSH with low free T4 suggests a pituitary problem or severe illness, not a primary thyroid problem. [1]
Look for interference
Severe illness, pregnancy, biotin supplements, steroids and amiodarone can change results. Repeat tests after recovery. [1]
Find the cause
Antibodies help: TPO antibodies suggest Hashimoto thyroiditis and TSH receptor antibodies suggest Graves disease. [2]
Common errors
- Ordering free T4 alone and missing a subclinical problem.
- Calling low TSH with low free T4 hyperthyroidism.
- Testing during severe illness without repeating later.
Common patterns (typical adult TSH about 0.4 to 4.0 mIU/L; use your lab's ranges) [1]
| TSH | Free T4 | Usual meaning |
|---|---|---|
| High | Low | Primary hypothyroidism |
| High | Normal | Subclinical hypothyroidism |
| Low | High | Hyperthyroidism |
| Low | Normal | Subclinical hyperthyroidism or high T3 only; check T3 |
| Low or normal | Low | Pituitary problem or severe illness |
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
VMS cases that train this skill
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCCPA PANCE Content Blueprint. VMS is not affiliated with these organizations. Updated: 2026-10-11.