MedicalResearch.com Interview with:
Joanna Klubo-Gwiezdzinska, M.D., Ph.D., M.H.Sc.
Assistant Clinical Investigator/Assistant Professor
Metabolic Disease Branch/NIDDK/NIH
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: People with intermediate- and high-risk differentiated thyroid cancer (DTC) are treated with surgical removal of the thyroid gland and radioactive iodine therapy. After surgery and initial treatment, the thyroid hormone levothyroxine is used for long-term management not only to replace appropriate physiologic thyroid hormones post-surgery, but also to suppress thyrotropin (TSH) release from the pituitary gland at supraphysiologic doses.
The current recommended American Thyroid Association TSH suppression goal in patients with a high-risk differentiated thyroid cancer presenting with distant metastases is less than 0.1mIU/ml, and between 0.1-0.5 mIU/ml for patients with intermediate-risk DTC presenting with local metastases to the neck lymph nodes. This TSH goal is much lower than physiologic TSH level, which ranges between 0.4-4.1 mIU/ml, depending on the measurement method and person’s age.
TSH suppression is used because some preclinical evidence suggests that TSH can stimulate growth of cancer cells. However, several preclinical studies show that thyroid hormones may also stimulate cancer growth. In addition, too much levothyroxine, leading to TSH suppression, may cause side effects such as abnormal heart rhythms and decreased bone mass.
In this study, based on a large multicenter database analysis, we found that continuous TSH suppression with levothyroxine was not associated with better progression-free survival and overall survival in patients with either intermediate- and high-risk differentiated thyroid cancer. The patients were followed for an average of 7 years after surgical thyroid cancer removal and radioactive iodine therapy. Continue reading