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Hydroxylase Antibodies

Addison's disease, or primary adrenal insufficiency, is most commonly caused by autoimmune destruction of the adrenal cortex and is characterized by the presence of adrenal cortex autoantibodies in the serum. Addison’s disease can occur sporadically or in combination with other autoimmune endocrine diseases, that together comprise Type I or Type II autoimmune polyglandular syndrome (APS).

The microsomal enzyme, 21-hydroxylase, is the primary antigen associated with Addison's disease. Antibodies to 21-Hydroxylase antibodies are the best marker of autoimmune Addison's disease, whether it presents alone, or as part of Type I or Type II APS. Testing for this antibody may be useful in the investigation of adrenal insufficiency and may also aid in the detection of those at risk of developing autoimmune adrenal failure in the future. The positive rate of hydroxylase antibody detection is summarized in the following table.

Healthy blood donors

6/243

Isolated Addison's disease

43/60

APS type I

11/12

APS type II

27/27

Type 1 diabetes mellitus

4/150

Type 2 diabetes mellitus

0/32

Grave's disease

1/77

Hashimoto's disease

1/67

Myasthenia gravis

0/35

Normals from Mayo NV Study

1/50

+ Insulin Antibody

0/5

+ Thyroid stimulating Immunoglobin

0/5

+ Anti-nuclear Antibodies

0/10

+ Rheumatoid Factor

0/10

A positive result indicates the presence of the antibody. Specimen requirement is a plain red top tube of blood.

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