Value of diagnostic radioiodine scintigraphy and thyroglobulin measurements after rhTSH injection.
Measurements of thyroglobulin (Tg) levels 72 h after administration of recombinant human thyrotropin (rhTSH) are recommended by the manufacturer in the follow-up of patients with differentiated thyroid carcinoma (DTC). In our department, Tg measurements are performed both 24 h and 72 h after administration of rhTSH, together with 72 h post rhTSH 131I whole body scintigraphy (WBS). The OBJECTIVE of this study is to compare the diagnostic usefulness of Tg measurements 24 and 72 h after rhTSH administration, and 131I WBS.


METHODS
181 patients were included who had been referred to our Nuclear Medicine Department for follow-up after 131I ablation of DTC. Tg measurements 24 h (Tg24) and 72 h (Tg72) after rhTSH, and 131I WBS, were done in all patients. The lower detection limit of Tg was 0,2 microg/l.


RESULTS
47 patients (26%) had detectable Tg levels: in 4/47 cases (8%) only Tg24 was detectable (always <1 microg/l), and in 6/47 cases (11%), only Tg72 was detectable. In 10/47 patients with detectable Tg-levels, Tg24 and Tg72 tested equally. In 27/47 cases, Tg24 was lower, and in 10/47 higher, than Tg72. Two patients with one or two positive Tg-test results also had a positive 131I WBS. In 8 patients (14%) only the 131I WBS was positive; an anatomical substrate for such a Tg-negative positive WBS was confirmed in only 2 patients.


CONCLUSIONS
Tg-measurement 72 hours after rhTSH injection reveals all clinically relevant detectable Tg-levels. Diagnostic 131I scintigraphy may be omitted, even in high-risk patients.
Verburg
F A
FA
University Medical Center Utrecht, Department of Nuclear Medicine, Utrecht, Netherlands. Verburg_E@klinik.uni-wuerzburg.de
de Keizer
B
B
de Klerk
J M H
JM
Lentjes
E G W M
EG
Lips
C J M
CJ
van Isselt
J W
JW
D002291:Carcinoma, Papillary / Q000097:blood / Q000601:surgery; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000601:surgery; D013972:Thyrotropin / Q000008:administration & dosage / Q000494:pharmacology*; D013974:Thyroxine / Q000627:therapeutic use
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine