How to deal with undetectable and low measurable serum thyroglobulin levels in the follow-up of patients with differentiated thyroid carcinoma?

Abstract

Serum thyroglobulin (Tg) was measured in 52 patients 3 months to 15 years (mean 5.3 years) after thyroidectomy with or without subsequent radioablation for differentiated thyroid carcinoma, before and after the interruption of suppressive thyroxine (T4) replacement therapy for 5 weeks. Whole body scintigraphy was carried out at the end of the T4 withdrawal period. Serum Tg was undetectable (< 3 \g=m\g/l ) in 38 patients on T4 therapy, in 18 the scintigraphy showed a minimal accumulation in the neck region and in 20 no uptake anywhere after withdrawal of T4. In the former group Tg rose in 10 patients to 4\p=n-\21\g=m\g/lwhen off T4 which seemed to correspond to the normal tissue left in situ, in the latter group Tg rose only in 2 patients to 5 and 21 \g=m\g/l ,respectively. Two patients out of 14 with detectable Tg on T4 had pulmonary metastases as uncovered by whole body scintigraphy (in one of them Tg rose from 12 \g=m\g/l on T4 to 1200 \g=m\g/l off T4) and 6 patients were suspected for having recidual cancer tissue (2 patients had a negative scintigraphy) because the Tg rose (66\p=n-\ 215 \g=m\g/l) over the upper limit of the reference range (< 50 \g=m\g/l ) after T4 withdrawal. In conclusion, in the follow-up of patients with differentiated thyroid carcinoma no routine scans are needed as long as serum Tg remains undetectable but further examinations are shortly warranted when detectable Tg is obtained during T4 suppression.

Diagnostic value of serum thyroglobulin measurements in the follow‐up of differentiated thyroid carcinoma, a structured meta‐analysis

“…As the category of patients without thyroid ablation, on thyroxine, comprised only three studies, data were not pooled. Sensitivity was 1·000 and specificity 0·750 in Valimaki and Lamberg (1985); however, this study contained only one tumour case. In Ronga et al .…”

“…The range for sensitivity was 0·500–1·000, for specificity 0·214–1·000, when patients with unspecified thyroid region activity were excluded. The studies with remarkably high specificity (Valimaki & Lamberg, 1985; Dadparvar et al ., 1995) were limited by the fact that they were small, and contained only few tumour cases. According to Table 1 and Fig.…”

The clinician and the thyroid

“…Its molecular structure and function have been studied for many years. Thus, serum hTg is an excellent marker for residual thyroid tissue after this kind of treatment, for local relapse of thyroid cancer and, most importantly, for the detection of distant metastases which may occur later in the course of the disease (Valimaki and Lamberg 1985). The development of RIAs to measure hTg made the discovery possible that hTg is a normal component of human serum; until 20 years ago, it was thought to be confined to the thyroid gland (Rawitch et al 1985).…”

Study of Serum Thyroglobulin in Differentiated Thyroid Carcinoma

“…The precise cut off values used depends on postoperative Thyroid Stimulating Hormone (TSH) [5,6,7] and the time of surgery. [8,9] Van herle who devised the original assay for thyroglobulin, states that serum thyroglobulin levels higher than 10 ng/ml raises the suspicion of thyroid remnant after thyroidectomy or presence of metastases. Such levels of 35±8.1 ng/ml were noted in the present study in 8 subjects.…”