Thyroid antibodies

I still adjust depending on the TSH value. I've never heard of adjusting based on antibodies.

UPTODATE

ANTITHYROID ANTIBODIES — Several antibodies against thyroid antigens have been described in chronic autoimmune thyroiditis. The antigens include:

• Thyroglobulin (Tg, formerly known as the colloid antigen)
  
• Thyroid peroxidase (TPO, formerly known as the microsomal antigen)
  
• The TSH receptor
  

Thyroglobulin (Tg) is synthesized by follicular cells and secreted into the lumen of the thyroid follicle, where it is stored as colloid. Thyroid peroxidase (TPO) catalyzes the iodination of tyrosine residues of Tg to form monoiodotyrosine and diiodotyrosine. Nearly all patients with Hashimoto's thyroiditis have high serum concentrations of antibodies to Tg and TPO. TSH receptor antibodies (TRAb) have been classified as stimulating, blocking, or neutral. TSH receptor antibodies of the stimulating variety (thyroid stimulating immunoglobulins) cause Graves’ disease. However, both TSH receptor blocking and stimulating antibodies are seen in patients with Graves’ disease. TSH receptor blocking antibodies may also be seen in patients with atrophic Hashimoto’s thyroiditis. The role of these antibodies in the pathogenesis of autoimmune thyroid disease is reviewed separately. (See "Pathogenesis of Graves' disease" and "Pathogenesis of Hashimoto's thyroiditis (chronic autoimmune thyroiditis)".)

Routine measurement of antithyroid antibodies is not necessary for the assessment of thyroid function. As an example, serum antithyroid peroxidase antibodies need not be measured in patients with overt primary hypothyroidism because almost all have chronic autoimmune thyroiditis. However, a test for antithyroid peroxidase antibodies may be useful to predict the likelihood of progression to permanent overt hypothyroidism in patients with subclinical hypothyroidism. (See "Subclinical hypothyroidism", section on 'Evaluation'.)

Measurement of TSH receptor antibodies (TRAb) is unnecessary for establishing the cause of hyperthyroidism if a radioiodine uptake has been obtained. However, TRAb measurements are being used increasingly as an alternative and may be useful when a radioiodine uptake is unavailable or contraindicated (eg, to distinguish Graves’ hyperthyroidism from postpartum thyroiditis in a nursing mother). TRAb measurements are also useful for assessing the likelihood of remission after a course of antithyroid drugs in patients with Graves’ disease. (See "Diagnosis of hyperthyroidism", section on 'Determining the etiology' and "Postpartum thyroiditis", section on 'Differential diagnosis' and "Thionamides in the treatment of Graves' disease", section on 'Can remission be predicted?'.)

The type of assay used to detect TRAb depends upon local availability. Thyroid stimulating immunoglobulin (TSI) assays measure the ability of the antibody to bind to the TSH receptor and stimulate adenylate cyclase production. While they are very specific for Graves’ disease, they are less sensitive and may be normal in mild hyperthyroidism. The second generation TSH receptor binding inhibitor immunoglobulin (TBII) assays measure stimulating, blocking, and neutral antibodies. They are more sensitive but may be less specific for Graves’ hyperthyroidism [25]

I have Hashimoto's thyroiditis and see my endocrinologist q3-4 months and he has never adjusted my Synthroid based on my antibodies. In fact my antibodies have only been drawn once. My endocrinologists makes adjustment based on my symptoms and my FT4, TSH, T3.

TSH...... Have you had a chance to look back in the record to see whats been happening? What does your consulting provider say?

The OP may NOT have a consulting provider. I don't and I never will have a "consulting provider".

Thyroid peroxidase antibody (TPO Ab) is initially drawn along with TSH w/ reflex to T4, T3 total, Free T3, Reverse T3 when a person is suspected for Hashimoto thyroiditis, idiopathic myxedema, Graves disease, and Riedel thyroiditis. TPO Ab is also drawn initially along with aldosterone, cortisol, ACTH when a person is suspected of adrenal crisis. Once a diagnosis is established, TPO Ab is not oftenly rechecked unless pt. quit taking meds for at least more than 6 months to yrs or in case of overdose of meds.

Synthroid and cytomel dosages are adjusted based on TSH, T4, T3. In the same way, steroids and vasopressors are based on cortisol, ACTH level for adrenal crisis. TPO Ab helps to diagnose severe hypo or hyper extremes of thyroid or adrenal gland and is not used to adjust dose.

We should not be adjusting meds based on thyroid antibodies. They are used to establish the Dx. Adjust based on the TSH/FT4 picture, with FT3 as an additional bit of info if you need it. And symptoms, of course!

Thanks all....I've been adjusting/monitoring pt's based on TSH/FT4 and 3 which is why it really threw me off to have this pt say hers needed to be adjusted based on Abs....

Thanks