The assay for thyroid stimulating immunoglobulins using cultured human thyroid cells.

Area of Science:

• Endocrinology
• Immunology
• Thyroidology

Background:

• Thyroid-stimulating immunoglobulins (TSI) are implicated in Graves' disease pathogenesis.
• Measuring TSI via cyclic AMP increases in thyroid cells is a reported detection method.
• Thyrotropin binding inhibitor immunoglobulins (TBII) are another marker used in thyroid disorder assessment.

Purpose of the Study:

• To compare the detection frequency of TSI versus TBII in patients with various thyroid disorders.
• To investigate the correlation between TSI, TBII, and thyroid hormone levels (T3, T4).

Main Methods:

• Analysis of immunoglobulin (Ig) fractions from 114 sera of 112 patients with thyroid disorders.
• Detection of TSI by measuring cyclic AMP increases in isolated thyroid cells.
• Detection of TBII by standard assays.

Main Results:

• TSI detected in 95.6% of untreated thyrotoxic Graves' disease patients, compared to 54.2% for TBII.
• TSI showed significant positive correlation with serum T3 and T4 levels.
• TSI was detected in all patients with relapsed Graves' disease, while TBII was rarely found.
• TSI was found in one Hashimoto's thyroiditis patient and three patients with exophthalmos without hyperthyroidism.

Conclusions:

• TSI appears to be a more sensitive marker than TBII for active Graves' disease, especially during relapse.
• TSI levels correlate with the severity of thyrotoxicosis.
• TSI may be present in other thyroid conditions, including hypothyroidism and exophthalmos.