Anti-Thyroid Microsomal Antibody

Sample for Anti-Thyroid Microsomal Antibody

1. The serum is needed.
2. The fasting sample is preferred.
3. Stop vitamins before taking the sample.

Pathophysiology of auto-antibodies of the thyroid gland:

1. The auto-antibodies are directed against various self-antigens like cellular components (Antimicrosomal antibodies) or proteins(thyroglobulins).
2. These autoantibodies are found in the autoimmune diseases of the thyroid gland.

The thyroid autoantigens are:

1. Thyroglobulin.
2. Thyroid microsomal antigen (the vesicle-like structure formed from the endoplasmic reticulum when cells are disrupted).
3. Thyroperoxidase (a component of thyroid microsomal antigen).
4. TSH-Receptor (Thyrotropin receptor).
5. Rarely auto-antigens are:
   1. TSH.
   2. T4 and T3

The thyroid auto-antibodies are:

1. Antithyroglobulin antibody.
2. Antimicrosomal antibody.
3. Anti-thyroid peroxidase antibody.
4. Long-acting thyroid-stimulating antibody (LATS) includes:
   1. TSI = thyroid-stimulating immunoglobulin.
   2. TSH-R antibody = thyroid hormone receptor antibody.

Antithyroid microsomal antibody: 

1. This test differentiates between Hashimoto’s thyroiditis and chronic lymphocytic thyroiditis in children.
   1. These are found more in chronic thyroiditis than antithyroglobulins antibodies.
2. These are present in 70% to 90% of Hashimoto’s thyroiditis.
3. This antibody is against the microsomes of the thyroid cells.
4. There is a cytotoxic injury to the thyroid follicles.

Anti-thyroid Microsomal Antibody: Antimicrosomal antibody and its value in thyroid diseases

A lab diagnostic method for thyroid microsomal antibody:

Thyroid microsomal antibodies can be detected by:

1. Complement fixation test.
2. Immunofluorescence of tissue biopsy.
3. Passive hemagglutination.
4. ELISA method.
5. Radioimmunoassay (RIA).
6. Normal Antimicrosomal antibodies:
   1. Negative = < 1:100
   2. 5% to 10% are present in healthy people without thyroid disease.

Antithyroid peroxidase antibody:

1. Anti-thyroid peroxidase autoantibodies are replacing atimicrosomal antibodies and anti-thyroglobulins.
2. This is recognized as the thyroid microsomes’ principal and possibly only autoantigen component.
3. This is suggested in routine in the case of autoimmune disease of the thyroid.
4. The thyroid microsomal antibodies are difficult to perform.
   1. There are irrelevant thyroid antigens, autoantibodies, and contamination of microsomes with thyroglobulin.
   2. The thyroperoxidase antibody eliminates these complications.
5. The RIA and chemiluminescence can detect these antibodies.
   1. The above two methods are more accurate than passive hemagglutination.
6. Antiperoxidase antibodies are seen in the following:
   1. These are seen in Hashimoto’s thyroiditis, idiopathic myxedema, and most cases.
   2. These are positive in 90% of the cases of Hashimoto’s thyroiditis.
   3. The high titer of these antibodies suggests Hashimoto’s thyroiditis, but its negative value does not rule out Hashimoto’s thyroiditis.
7. Anti-thyroid peroxidase antibody is seen in the following:
   1. A titer of >1:1,000 is seen in Grave’s disease and Hashimoto’s thyroiditis.
   2. Grave’s disease.
   3. Diabetes mellitus type 1.
   4. It may be seen in nonimmune thyroid disease.
8. Normal anti-thyroid peroxidase antibody:
   1. Titer = <1:100

Thyrotropin receptor antibody (TSH-R antibody):

1. Some immunoglobins bind to the thyroid cell membrane near or to the TSH-receptor site.
2. These are often seen in Grave’s disease patient’s blood.
3. These are also found in other thyroid autoimmune diseases.
4. Their function is variable:
   1. In some cases, they may have a stimulatory effect.
   2. In some cases, they block the TSH-receptor site and decrease thyroid function.
   3. In some, there may be no effect.
5. Their functional role may be in the pathogenesis of Grave’s disease. It is found as a long-acting thyroid stimulator in the serum of these patients.

Antithyroid Ab Positive in:

1. Chronic thyroiditis (40 to 70 %).
2. Thyrotoxicosis (Grave’s disease).
3. Hypothyroidism.
4. Hashimoto’s thyroiditis.
5. Pernicious anemia.
6. Other autoimmune diseases like Rheumatoid arthritis and systemic lupus erythematosus.

• Table showing various thyroid diseases and auto-antibodies

• LATS antibodies are of two types:
  • TSI = Thyroid stimulating immunoglobulin.
  • TSH-R antibody = Thyroid-stimulating hormone receptor antibody.
• Please see more details on the Antithyroglobulin antibody.+

Antimicrosomal autoantibodies increased level seen in:

1. Hashimoto’s thyroiditis.
2. Thyroid cancer.
3. Myxedema.
4. Sjogren’s syndrome.
5. Goiter.
6. Autoimmune hemolytic anemia.
7. Lupus erythematosus.
   Antimicrosomal antibodies positivity in various diseases:

   Clinical disease	Antimicrosomal antibody	Antithyroglobulin antibody
   Grave’s disease	75% (71% to 86%)	55% (29% to 65%)
   Hashimoto’s disease	97% (92% to 100%)	70% (50% to 86%)
   Nontoxic nodular goiter	27%	5% to 50%
   Primary myxedema	75% (67% to 86%)	55% (50% to 64%)
   Thyroid carcinoma	20%	20%
   Female, normal	15%	2% to 20%
   Male, normal	0% to 3%	0% to 2%

• Either hemagglutination or immunofluorescent methodology can do the above tests.

Summary of thyroid autoantibodies:

1. Anti-thyroglobulin antibody:

1. These antibodies are a sign of Hashimoto’s thyroiditis.
2. There is a high level of these antibodies.

2. Thyroid peroxidase antibody:

1. These antibodies are a sign of Hashimoto’s thyroiditis.
2. These are autoimmune antibodies that lead to hypothyroidism.
3. Grave’s disease is hyperthyroidism.

3. Thyroid-stimulating hormone (TSH) receptor:

1. These antibodies are signs of Grave’s disease.

4. Thyroid microsomal antibodies:

1. These antibodies are present in Hashimoto’s thyroiditis.
2. It differentiates Hashimoto’s thyroiditis from chronic lymphocytic thyroiditis.

Questions and answers: