Serum Thyroglobulin as a Marker for Differential Diagnosis of Hyperthyroidism.

Objective: To evaluate the role of serum thyroglobulin (TG) as a biochemical marker for differential diagnosis of common aetiologies of hyperthyroidism.

Study Design: Comparative cross-sectional study. Place and Duration of the Study: Department of Chemical Pathology and Endocrinology, Armed Forces Institute of Pathology (AFIP), Rawalpindi, Pakistan, from October 2023 to March 2024.

Methodology: One hundred and forty-eight patients with clinical or biochemical hyperthyroidism were enrolled in the study. Samples were taken for serum thyroglobulin and evaluated for different causes of hyperthyroidism as demonstrated on the thyroid scan. Serum TG levels were measured using a chemiluminescence immunoassay and levels >42 ng/ml were considered elevated. Relationship between TG levels and different causes of hyperthyroidism was determined via independent samples non-parametric Kruskal-Wallis test.

Results: The study found that 76.3% (n = 113) of patients had raised TG levels, with significant differences in median TG levels observed among the different hyperthyroidism aetiologies. Thyroiditis exhibited the highest median TG levels (202.5 ng/ml), followed by toxic adenoma (139 ng/ml) and toxic multinodular goitre (102 ng/ml), while Graves' disease had the lowest levels (34 ng/ml). Sensitivity of thyroglobulin to detect thyroid disease was 76% while specificity came out to be 100%. Positive predictive value (PPV) was 100% while negative predictive value (NPV) was 20.45%.

Conclusion: Serum TG levels vary markedly among different aetiologies of hyperthyroidism with the highest levels in thyroiditis and the lowest in Graves' disease.

Key Words: Thyroglobulin, Hyperthyroidism, Graves' disease, Thyroiditis.