Serum thyroglobulin differentiated thyroid carcinoma: histological and metastatic classification.

Serum thyroglobulin (tg) levels were measured in 112 patients with proved differentiated thyroid carcinoma (6 pre-operative, 32 post-operative and 74 in whom thyroidectomy was followed by radioiodine treatment). The tg levels were within the normal range in patients who had a residual mass in the neck region after surgery and who were in remission. The patients with metastases showed a wide range (undetectable to microgram quantities) of tg in circulation. The analysis of serum tg with respect to histology showed that the follicular variety of carcinoma tends to show higher tg in serum than the papillary type. Metastatic involvement of bone was associated with much higher serum tg levels than other sites such as lung and lymph node. Thirteen patients with bone metastases of non-thyroidal primary origin had tg levels within the normal range. Serum tg estimation is useful in excluding thyroid as a primary site in patients with bone metastases of unknown primary origin.