Endocrine Abstracts

Introduction: A value of thyroglobulin (Tg) undetectable under treatment with levothyroxine (LT) does not exclude residual/metastatic disease; this can be found in 18–35% of patients after recombinant TSH-stimulated Tg (sTg) measurements.

Objective: Evaluating the role of recombinant TSH-stimulated thyroglobulin (sTg) measurements in patients with differentiated thyroid carcinoma, treated with suppressive LT doses, with basal Tg (bTG)<1 ng/ml.

Methods: Retrospective evaluation of patients with differentiated thyroid carcinoma with bTg<1 ng/ml submitted to sTg measurements between 01/01/2008–31/12/2009. Patients were divided into two groups: bTg<0.2 ng/ml (group 1); bTg between 0.2–1 ng/ml (group 2). Patients with anti-Tg were excluded. Limit of detectable Tg in our institution 0.2 ng/ml.

Results: n=96; 80.2% ♀; diagnosis age=41.8±13.4year; 78.1% papillary (10.4% microcarcinomas), 11.5% follicular. Ablative radioiodine dose=97.1±29.3 mCi. 73 patients belonged to group 1 and 23 to group 2. There was no statistically significant relationship between these groups with respect to gender, diagnosis age, presence of nodal metastasis, stage or radioiodine dose. All patients of group 2 had papillary carcinoma.

There was no statistically significant relationship between sTg>2 ng/ml and gender, diagnosis age, histology, presence of nodal metastases or radioiodone dose. 31.3% of patients with sTg>2 ng belong to stage IV while in the group with sTg<2 ng/ml only 9.3% belong to this stage (P=0.050). There was a positive correlation between bTg and sTg (r=0.329, P=0.001). There was no statistically significant relationship between sTg and gender, diagnosis age, histology, presence of nodal metastasis, stage or iodine dose.

Conclusions: In Group 1, 91.9% with bTg<0.2 ng/ml kept sTg within normal range. In this group, 83.3% with sTg>2 ng/ml had multifocal disease. In Group 2, 56.5% had sTg<2 ng/ml; 60% of this group with sTg>2 ng/ml showed capsule`s invasion. In 50% of patients with sTg>2 ng/ml was detected locoregional disease. There was no distant metastasis.