OP7 – Serum Thyroglobulin Normalized to Thyroid Nodule Size as a Predictor of Malignancy

      Verma, Neil1; Gabra, Nathalie1; Forest, Veronique-Isabelle2; Tamilia, Michael3; Hier, Michael P.2; Payne, Richard J.1,2 1 Department of Otolaryngology – Head and Neck Surgery, McGill University Health Centre, Montreal, Quebec, Canada 2 Department of Otolaryngology – Head and Neck Surgery, Sir Mortimer B. Davis – Jewish General Hospital, McGill University, Montreal, Quebec, Canada 3 Department of Endocrinology and Metabolism, Sir Mortimer B. Davis – Jewish General Hospital, McGill University, Montreal, Quebec, Canada Background: Thyroid nodules are found in 4-8% of adults on clinical examination with approximately 5% of nodules ultimately being malignant 1. Our group has previously developed the McGill Thyroid Nodule Score (MTNS) to assess pre-operative risk of malignancy. Incorporation of criteria such as serum thyroglobulin has improved the sensitivity of the MTNS. We hypothesized that normalization of thyroglobulin levels to nodule size would provide a better indication of its malignant potential. Methods: Retrospective study of patients undergoing partial or total thyroidectomies at McGill University teaching hospitals. Exclusion criteria for the study included patients without documented pre-operative thyroglobulin levels or ultrasound investigations. Serum thyroglobulin levels were measured based on standard diagnostic immunoassays. Nodules were classified as benign or malignant based on final histological diagnosis. All study protocols were approved by McGill University’s Institutional Review Board. Results: Serum thyroglobulin levels were significantly higher in malignant compared to benign nodules (54.38ug/L ± 4.97 vs 177.1ug/L ± 39.9). Normalizing serum thyroglobulin levels to nodule size revealed differences between malignant and benign nodules (49.15ug/L*cm ± 8.09 vs 21.68ug/L*cm ± 2.05). Average nodule size for malignant and benign nodules was not significantly different (2.80cm  ± 0.15 vs. 2.88cm  ± 0.16) Stratification for nodule size into groups 1-1.9cm, 2-2.9cm, ?3 cm demonstrated significant differences between benign and malignant nodules’ normalized serum thyroglobulin levels for nodules larger than 2cm. Conclusions: The role of serum thyroglobulin has been controversial in terms of its use for predicting malignancy prior to surgery. Normalizing serum thyroglobulin levels to nodule size may be useful in the assessment of indeterminate thyroid nodules. References:
    1. Gharib, H., Papini, E., Paschke, R. et al. J Endocrinol Invest (2010) 33: 287. doi:10.1007/BF03346587


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