Thyroperoxidase antibodies (= TPO-Ak or anti-TPO; thyroid peroxidase antibodies = PAK) or antibodies against microsomal thyroid antigen (microsomal antibodies, microsomal auto-AK = MAK) are thyroid autoantibodies that may be present in the blood in various diseases of the thyroid gland.
Thyroperoxidase (thyroid peroxidase) represents an important component in the biosynthesis of thyroid hormones. It is the key enzyme for the iodination of thyroglobulin and for the coupling of two dityrosines. The thyroid peroxidase antibody is directed against the enzyme thyroidea peroxidase, which catalyzes iodination.
The thyroperoxidase antibody (TPO-Ak) is positive in five percent of the healthy population! Thus, a positive finding is not proof of the presence of autoimmune thyroid disease. In addition, microsomal antibodies (MAK) can also be determined; however, these are less specific.
The procedure
Material needed
- Blood serum
Preparation of the patient
- Not necessary
Disruptive factors
- None known
Standard values
TPO-Ak
| Normal value in U/ml | <80 U/ml |
| Borderline finding | 80-150 U/ml |
| Positive | ≥ 150 U/ml |
| Reference values | < 34 kU/I |
MAK
| Standard value in U/ml | < 100 |
| Positive | ≥ 150 U/ml |
Indications
- Suspected thyroid dysfunction.
- Alopecia (hair loss)
- Habitual abortion – ≥ three miscarriages of unclear cause.
- Addison’s disease (primary adrenocortical insufficiency/underactivity of the adrenal cortex).
Interpretation
Interpretation of increased values
- Hashimoto’s thyroiditis (autoimmune thyroiditis) – autoimmune disease of the thyroid gland leading to hypothyroidism (underactive thyroid) (detection frequency* : 90%).
- Primary myxedema (atrophic autoimmune thyroiditis) [detection frequency* : 40-70%]
- Graves’ disease – autoimmune disease of the thyroid gland leading to hyperthyroidism (hyperthyroidism) [detection frequency* : 60-80%]
- Postpartum thyroiditis – special form of chronic thyroiditis that occurs after childbirth. In this case, a temporary hyperthyroidism (hyperthyroidism) develops, which is followed by a temporary hypothyroidism with spontaneous healing. [Detection frequency* : 50-70%]
- Thyroiditis de Quervain – subacute thyroiditis; rare form of thyroiditis (often with very severe pain), which often occurs after viral infections and shows transient symptoms of initially hyper- and later hypothyroidism (hyper- and hypothyroidism) [detection frequency* : < 5%].
- Thyroid autonomy (rare) [detection frequency* : circa 5%]
* TPO-Ak/MAK