• 4/12/2004
  • New York
  • Amy Norton
  • Journal of Nuclear Medicine

A standard post-surgery routine that can leave thyroid cancer patients feeling run-down for weeks may be largely unnecessary, new research suggests. The procedure, widely used for decades, calls for patients who have had their cancerous thyroid glands removed to go off of their normal hormone replacement therapy for six to eight weeks so that they can receive follow-up care.

But in the new study, researchers found that just two weeks off of thyroid replacement was sufficient for about 90 percent of the 284 patients they assessed. This shortened time frame could cut the amount of time that patients suffer the side effects of stopping their normal hormone replacement therapy, according to the study authors.

The thyroid is a gland in the neck that secretes hormones that help regulate metabolism. When thyroid hormone levels drop too low, a condition called hypothyroidism, metabolism slows, and symptoms such as fatigue, poor memory, weight gain and depression set in. So when the gland is removed due to cancer, patients must take synthetic replacement hormones for life. However, doctors have to temporarily stop patients’ replacement therapy to give them radioactive iodine. Because the thyroid gland absorbs nearly all of the iodine that enters the body, radioactive iodine can be used to destroy cancerous thyroid cells. Alternatively, iodine can be given in a small amount to reveal on X-rays any residual cancer remaining after surgery.

When patients stop their hormone replacement, the brain produces more thyroid-stimulating hormone (TSH), which causes any remaining thyroid cells in the body to become “really hungry for iodine,” Dr. Perry W. Grigsby, the study’s lead author, explained.

So once TSH levels are high enough, any thyroid cells remaining after cancer patients’ surgery will soak up the radioactive iodine. Doctors have traditionally thought that to get this TSH elevation, patients have to reduce thyroid medication levels for four to six weeks, then go off hormone replacement completely for two weeks. The problem is that this sends them into weeks of what Grigsby called “profound” hypothyroidism. “They feel really lousy,” he told Reuters Health. “They’re tired, worn out.”

To minimize the time that patients go through this misery, Grigsby and his colleagues at Washington University School of Medicine in St. Louis have relied on simply stopping patients’ thyroid hormone therapy for two weeks.
Their study, reported in the Journal of Nuclear Medicine, reviewed the records of 284 of these patients. It found that nearly 90 percent had sufficiently high TSH levels after about two weeks off of their medication.

According to Grigsby, the standard, six- to eight-week routine arose from a recommendation made several decades ago that was essentially based on logic rather than scientific evidence. The rationale was that giving patients a weaker thyroid medication for several weeks would allow the body to clear the hormone–and boost TSH levels–more quickly once the medication was stopped. But the approach has not been backed up by evidence. “I think it’s been basically a medical myth,” Grigsby noted.

In contrast, he said he thinks there is sufficient science to support his team’s abbreviated tactic. Two other recent studies, he and his colleagues note, have also shown that at least 90 percent of patients reach the needed TSH level after two to three weeks off of hormone replacement