A multicenter international study, including Johns Hopkins, has found that after surgery for thyroid cancer, giving genetically engineered human thyroid-stimulating hormone (rhTSH) before radioiodine treatment avoids the previous need to stop thyroid replacement therapy and the miserable side effects that go with it.
The study, led by Paul Ladenson, M.D., director of the Division of Endocrinology at The Johns Hopkins University School of Medicine, and Furio Pacini at the University of Siena in Italy, was reported in the December online edition of the Journal of Clinical Endocrinology and Metabolism.
Typically, radioiodine treatment for cancer of the thyroid gland requires temporary discontinuation of thyroid hormone replacement for several weeks, leading to weight gain, constipation, fatigue, slowed thinking, depressed mood, muscle cramps, intolerance of cold temperatures and other symptoms. "This study shows that patients who use a recombinant form of TSH can continue their thyroid replacement therapy and enjoy a better quality of life during their cancer treatment," Ladenson says.
Thyroid cancer is first treated by surgical removal of the gland in the neck, often followed by radioactive iodine treatment to remove any remaining thyroid tissue.
Once the thyroid is diseased or removed, it no longer produces the hormones T4 (thyroxine) and T3 (triiodothyronine), which help regulate heart rate, blood pressure, body temperature and weight. Therefore, it is essential to add back the thyroid hormone L-thyroxine to keep the body functioning normally. Paradoxically, for radioiodine treatment to be effective, thyroid hormone treatments previously had to be suspended, according to Ladenson. Suspending hormone treatments stimulates the pituitary gland to produce thyroid-stimulating hormone (TSH). TSH stimulates any remaining thyroid tissue to concentrate the radioiodine, which can then eliminate remaining thyroid tissue. Once inside the cell, radioiodine emits beta particles that damage the DNA in thyroid cells without affecting surrounding tissues, according to Ladenson.
TSH made by the pituitary gland and rhTSH produce equivalent biological actions, according to Ladenson, and there are only slight structural differences.
"This multi-institutional study proved that rhTSH is just as effective as the TSH produced by the body in destroying these remaining thyroid cells," Ladenson says.
This randomized, controlled, study involved 60 patients from four centers in Europe and five in North America. The first patient was enrolled on Dec. 17, 2001, and the last patient completed the final study visit on Sept. 26, 2003.