Thyroid Antibodies
Immune proteins that attack the thyroid gland. Used to diagnose autoimmune thyroid conditions like Hashimoto's and Graves' disease.
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What are Thyroid Antibodies?
Thyroid antibodies are immune system proteins that mistakenly target components of your thyroid gland. Their presence indicates autoimmune thyroid disease.
The main types are:
- TPO Antibodies — Attack thyroid peroxidase enzyme
- Thyroglobulin Antibodies (TgAb) — Attack thyroglobulin protein
- TSI (Thyroid-Stimulating Immunoglobulin) — Stimulate the thyroid (causes Graves')
Why They Matter
Confirming Autoimmune Cause
When thyroid function is abnormal, antibodies confirm whether the cause is autoimmune. This affects treatment decisions and monitoring.
Hashimoto's Thyroiditis
90%+ of Hashimoto's patients have elevated TPO and/or thyroglobulin antibodies. The condition slowly destroys the thyroid, leading to hypothyroidism.
Graves' Disease
TSI antibodies are specific for Graves' disease, causing the thyroid to overproduce hormones (hyperthyroidism).
Risk Prediction
Positive antibodies in someone with normal thyroid function predict higher risk of developing thyroid problems, especially:
- During pregnancy
- With age
- Under stress
Testing Approach
- TPO antibodies are tested first (most common)
- Thyroglobulin antibodies added if TPO is negative but autoimmune disease is suspected
- TSI tested specifically for Graves' disease