, Volume 23, Issue 2, pp 131-136
Date: 19 Feb 2009

Influence of thyroid-stimulating hormone on 18F-fluorodeoxyglucose and 99mTc-methoxyisobutylisonitrile uptake in human poorly differentiated thyroid cancer cells in vitro

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Abstract

Objective

In poorly differentiated thyroid cancer originating from thyroid follicular cells, the ability to concentrate iodine is lost. This makes recurrence undetectable by 131I whole-body scan. In this situation, other radiopharmaceuticals, such as 18F-fluorodeoxyglucose (18F-FDG) and technetium-99m-methoxyisobutylisonitrile (99mTc-MIBI), are used to evaluate recurrence or metastasis. Some reports suggest that 18F-FDG uptake is increased by thyroid-stimulating hormone (TSH) stimulation. This study aimed to determine the influence of TSH on 18F-FDG and 99mTc-MIBI uptake in human poorly differentiated thyroid cancer cells in vitro.

Materials and methods

The cells were stimulated with 1000 μU/ml of recombinant human thyroid-stimulating hormone (rhTSH) for 1 day, 3 days, and 5 days. Each cell was incubated with 0.5 MBq/ml-1 MBq/ml of 18F-FDG or 0.5 MBq/ml-1 MBq/ml of 99mTc-MIBI for 1 h at 37°C. The uptake of each radiopharmaceutical in the cells was quantified as a percent of whole radioactivity per total viable cell number. The quantification of glucose transporter 1, 2, 3 and 4 mRNA expression was measured using RT-PCR.

Results

TSH stimulation increased 18F-FDG uptake in a time-dependent manner. Following 5 days of rhTSH stimulation, 18F-FDG uptake was approximately 2.2 times that of the control. The increase in 18F-FDG uptake following rhTSH stimulation was correlated to the increase in GLUT4 mRNA level. The GLUT1 mRNA level was unchanged. An increased uptake of 99mTc-MIBI was observed with a pattern similar to that of 18F-FDG. The 99mTc-MIBI uptake was approximately 1.5 times that of the control 5 days later.

Conclusions

These results suggest that TSH stimulates 18F-FDG and 99mTc-MIBI uptake in poorly differentiated papillary thyroid cancer, and therefore 18F-FDG-PET or 99mTc-MIBI scans under TSH stimulation may be more accurate than under suppression.