Thyroid growth-blocking antibodies in primary myxoedema

Area of Science:

• Endocrinology
• Immunology
• Pathology

Background:

• Adult primary myxoedema involves autoimmune thyroiditis, leading to thyroid gland destruction and hormonal failure.
• Pathogenesis involves antibodies against thyroglobulin (TgHA) and microsomal antibodies (McHA), alongside cell-mediated immunity.
• High levels of thyroid-stimulating hormone (TSH) fail to stimulate thyroid regrowth in myxoedema, suggesting blocking factors.

Purpose of the Study:

• To investigate the role of blocking antibodies in the pathogenesis of adult primary myxoedema.
• To determine if immunoglobulins from myxoedema patients inhibit the trophic effect of TSH on the thyroid gland.

Main Methods:

• Utilized an in vitro system to assay the trophic effect of TSH.
• Measured DNA synthesis via Feulgen cytophotometry as an indicator of TSH trophic effect.
• Assessed immunoglobulins from patients with primary myxoedema and thyrotoxic Graves' disease.

Main Results:

• Immunoglobulins from patients with adult primary myxoedema were found to block the trophic effect of TSH in vitro.
• This blocking effect contrasts with the growth stimulation observed with immunoglobulins from patients with Graves' disease.

Conclusions:

• The study identifies blocking antibodies in primary myxoedema that interfere with TSH action.
• These blocking antibodies contribute to the thyroid gland's unresponsiveness to TSH, explaining the disease's progression.