🔬 Men's Health
Thyroid Tests Explained
TSH, T3, T4 — what your thyroid results actually mean
Thyroid function tests (TFTs) are among the most commonly ordered blood tests in Nigeria — yet patients frequently receive results without adequate explanation. 'Your thyroid is fine' or 'your thyroid is off' leaves most patients confused. This guide explains what TSH, free T4, and free T3 mean, what abnormal results indicate, and what happens next.
When to Seek Help
Any abnormal thyroid resultAlways discuss with a doctor — do not interpret results in isolation or self-medicate based on online research.
Normal thyroid result but ongoing symptomsResults must be interpreted alongside clinical symptoms — a 'normal' TSH does not exclude all thyroid pathology.
TSH above 10 or below 0.1These values usually require treatment — see a doctor promptly.
Tests & Diagnosis
🧪 TSH (Thyroid-Stimulating Hormone)
Produced by the pituitary gland. It rises when the thyroid is underactive (hypothyroidism) and falls when the thyroid is overactive (hyperthyroidism). TSH is the single best screening test. Normal range: 0.5–4.0 mIU/L (varies slightly by lab).
🧪 Free T4 (free thyroxine)
The main hormone produced by the thyroid. Low free T4 confirms hypothyroidism when TSH is elevated. Normal range: 12–22 pmol/L.
🧪 Free T3 (free triiodothyronine)
The active form of thyroid hormone — mostly converted from T4 in the tissues. Useful in hyperthyroidism (T3 toxicosis) and monitoring. Not routinely needed for initial diagnosis.
🧪 Anti-TPO antibodies (anti-thyroid peroxidase)
Elevated in Hashimoto's thyroiditis and Graves' disease. Confirms autoimmune cause. Normal: below 34 IU/mL (lab-dependent).
🧪 Anti-thyroglobulin antibodies
Also elevated in autoimmune thyroid disease. Often measured alongside anti-TPO.
🧪 TSH receptor antibodies (TRAb)
Specific for Graves' disease. Elevated confirms the autoimmune cause of hyperthyroidism.
Frequently Asked Questions
Why does TSH go up when the thyroid is underactive?
The pituitary gland (at the base of the brain) senses low thyroid hormone levels in the blood and releases more TSH to stimulate the thyroid to produce more. It is a feedback loop: low thyroid output = high TSH = more stimulation. Elevated TSH is therefore the first sign that the thyroid is struggling — often before T4 falls.
Why are my T3 and T4 levels checked if TSH is the main test?
TSH is the best screening test, but T3 and T4 confirm the diagnosis and degree of dysfunction. TSH alone can occasionally give misleading results — for example, in pituitary disease (causing secondary hypothyroidism with low TSH and low T4), or in the early stages of Graves' disease.
What does it mean if my anti-TPO antibodies are high but my TSH is normal?
High anti-TPO with normal TSH = Hashimoto's thyroiditis without overt hypothyroidism. The immune attack is present but the thyroid is still compensating. These people are at increased risk of developing hypothyroidism over time — annual TSH monitoring is recommended.
Can thyroid tests be affected by illness or medications?
Yes — severe illness (non-thyroidal illness syndrome) alters thyroid tests without true thyroid disease. Biotin supplements (commonly taken in Nigeria for hair loss) falsely lower TSH and elevate T4 in some assays — stop biotin for 48 hours before a thyroid test. Amiodarone, heparin, and certain other medications affect results.
How often should I have my thyroid checked?
For monitoring on treatment (levothyroxine or antithyroid drugs): every 6–8 weeks when adjusting doses; annually once stable. For known Hashimoto's thyroiditis with normal TSH: annually. For a family history of thyroid disease: every 2–3 years. In pregnancy: each trimester.