Tg, short for thyroglobulin, is a major product of the thyroid gland, serving as a macromolecular precursor of thyroid hormone biosynthesis. It also regulates thyroid-specific gene expression and follicle function in conjunction with thyroid-stimulating hormone (TSH) and iodide. Tg can stimulate the growth of thyroid cells in a concentration-specific manner, independent of TSH/cAMP stimulation [2].

Regarding its diagnostic value, thyroglobulin washout of fine-needle aspiration (FNA-Tg) is useful in detecting lymph node metastases from papillary thyroid cancer. High serum Tg is positively correlated with FNA-Tg, and FNA-Tg shows excellent diagnostic performance, though caution is needed when serum Tg is higher than 10 ng/ml [1]. The optimal cutoff value of FNA-Tg should be selected according to the thyroid status to ensure efficient diagnosis of cervical metastatic lymph nodes of papillary thyroid carcinoma, and serum Tg, TSH, and TgAb do not affect the diagnostic performance of the optimal cutoff value of FNA-Tg [3]. Also, in differentiated thyroid carcinoma patients with detectable Tg and negative 131I -scan, Tg kinetics (Tg -doubling time and Tg -velocity) can help predict 2 -[18F]-FDG -PET/CT results [4].

In conclusion, Tg is crucial for thyroid hormone biosynthesis and thyroid follicle function regulation. Its role in the diagnosis of papillary thyroid cancer-related lymph node metastases and prediction of PET/CT results in differentiated thyroid carcinoma patients has been revealed through various studies. Understanding Tg can provide insights into thyroid-related disease diagnosis and management.

References:

1. Wang, Jiahui, Jiang, Xianfeng, Xiao, Guizhou, Zhou, Weiping, Hu, Yan. 2020. Excellent diagnostic performance of FNA-Tg in detecting lymph nodes metastases from papillary thyroid cancer. In Future oncology (London, England), 16, 2735-2746. doi:10.2217/fon-2020-0213. https://pubmed.ncbi.nlm.nih.gov/32812450/

2. Noguchi, Yoshihiko, Harii, Norikazu, Giuliani, Cesidio, Suzuki, Koichi, Kohn, Leonard D. 2009. Thyroglobulin (Tg) induces thyroid cell growth in a concentration-specific manner by a mechanism other than thyrotropin/cAMP stimulation. In Biochemical and biophysical research communications, 391, 890-4. doi:10.1016/j.bbrc.2009.11.158. https://pubmed.ncbi.nlm.nih.gov/19951699/

3. Sun, Jingjing, Li, Peipei, Chen, Xiao, Yu, Qiujie, Li, Li. 2021. The influence of thyroid status, serum Tg, TSH, and TgAb on FNA-Tg in cervical metastatic lymph nodes of papillary thyroid carcinoma. In Laryngoscope investigative otolaryngology, 7, 274-282. doi:10.1002/lio2.717. https://pubmed.ncbi.nlm.nih.gov/35155808/

4. Albano, Domenico, Tulchinsky, Mark, Dondi, Francesco, Bertagna, Francesco, Giubbini, Raffaele. 2021. The role of Tg kinetics in predicting 2-[18F]-FDG PET/CT results and overall survival in patients affected by differentiated thyroid carcinoma with detectable Tg and negative 131I-scan. In Endocrine, 74, 332-339. doi:10.1007/s12020-021-02755-5. https://pubmed.ncbi.nlm.nih.gov/34014437/