Abstract
1332
Objectives: There are two means of TSH stimulation to enhance radioiodine uptake (RAIU) in using I-131 to detect or ablate residual/recurrent differentiated thyroid cancer (DTC). Thyroxin withdrawal (TW) for >4 weeks represents a chronically increasing TSH mode while rhTSH injection in 48 hours denotes an abrupt presence of high TSH level. To compare the effects of the two modes of TSH stimulation in Na+/I- symporter (NIS)-mediated RAIU and thyroglobulin (Tg) synthesis in DTC, we conducted a study using organotypic cultures of surgical samples allowing TSH stimulation ex vivo to examine RAIU and Tg level in a pair-wise comparison manner.
Methods: Surgical samples of DTCs were used for cultures. In addition to control group (no TSH added), experimental groups included (1) Gp1 with stepwise TSH increasing up to 2 mIU/ml in 1 week and (2) Gp2 with acute dosing of TSH 5.0 mIU/ml in the last 24 hours, with such design to allow tissues exposing to approximate 120 mIU-hour. I-125 uptake assay and Tg was determined from the culture tissues and pertinent media. The mRNA expression of NIS and Tg was quantified by RT-real time PCR from the cultured tissues.
Results: 16 samples were collected. As normalized to the controls, (1) no significant difference of TSH-induced RAIU in Gp1 and Gp2 (3.4+/- 1.7 vs. 3.4 +/- 2.1, p=0.09); (2) 2.9-fold higher increment of Tg concentration in Gp2 than Gp1 and (3) significant higher NIS mRNA and Tg mRNA expression in Gp2 than in Gp1.
Conclusions: Our data supports the clinical observation that similar effects of TW and rhTSH to facilitate RAIU, but the discrepancy between two different modes of TSH stimulation to induce rise of Tg level, NIS and Tg mRNA expression require further research.
- Society of Nuclear Medicine, Inc.