Toxic multinodular goiter: a variant of autoimmune hyperthyroidism

Area of Science:

• Endocrinology
• Immunology
• Nuclear Medicine

Background:

• Toxic multinodular goiter (TMG) is a common cause of hyperthyroidism.
• The etiology of TMG is not fully understood, with some cases potentially linked to autoimmune processes.

Purpose of the Study:

• To investigate the potential autoimmune basis in a subgroup of patients with toxic multinodular goiter.
• To differentiate TMG subtypes based on thyroid-stimulating immunoglobulin (TSI) activity and scintiscan patterns.

Main Methods:

• Measurement of TSI activity using a sensitive bioassay with cultured human thyroid cells.
• Classification of TMG patients based on scintiscan patterns (Type A: diffuse uptake, Type B: discrete nodules).
• Comparison of clinical and laboratory features between TSI-positive and TSI-negative TMG subgroups.

Main Results:

• All patients with active Graves' disease showed detectable TSI activity.
• TSI was undetectable in patients with toxic adenoma, cold nodules, and most nontoxic goiters.
• A subgroup of TMG patients (n=11) were TSI-positive, predominantly exhibiting a Type A scintiscan pattern.
• TSI-positive TMG patients (Type A) were younger and had more autoimmune markers (antibodies, ophthalmopathy) than TSI-negative Type B patients.

Conclusions:

• A subset of TMG patients (Type A scintiscan) likely represents a variant of autoimmune hyperthyroidism (Graves' disease).
• Another subset of TMG patients (Type B scintiscan) appears to have non-autoimmune hyperthyroidism, akin to toxic adenoma.
• Distinguishing these subgroups is crucial for understanding TMG pathogenesis and guiding treatment.