Genetically Engineered Thyroid Test
By Sean Henahan, Access Excellence
Baltimore, MD (9/30/97)- A genetically engineered form
of human thyroid-stimulating hormone offers an effective and safer alternative
to the cnventional test now used, report researchers at Johns Hopkins University.
The research invovled recombinant human thyroid-stimulating hormone
(rhTSH), a synthetic form of thyroid-stimulating hormone, the hormone produced
in the pituitary gland that stimulates the thyroid to release an essential
hormone for regulating metabolism. Ordinarily, patients receiving chemotherapy
for thyroid cancer need to stop taking their thyroid medications for TSH
testing. This can cause a host of problems including fatigue, depression
and weight gain. The new study showed that rhTSH facilitated accurate testing
for recurrent cancer while patients stayed on their usual thyroid hormone
suppression drugs.
"This could revolutionize the way we manage the health care of
patients with thyroid cancer," says Paul W. Ladenson, M.D., director of
endocrinology and metabolism at Johns Hopkins. "In most patients, the test
quality with the synthetic compound is the same or better than with traditional
hormone withdrawal and with a markedly higher quality of life for patients."
The research represents a culmination of nearly ten years of research.
In 1988, members fo the research team discovered the gene for human thyroid-stimulating
hormone. This was the key step needed for the development of the synthetic
TSH and the new test that followed.
In the current study, the researchers evaluated 127 people who had part
or all of their thyroid gland removed because of cancer. Each patient had
a test called a radioiodine scan to look for recurrence of cancer.
The first scan was done while patients took both their thyroid hormone
suppression drug and rhTSH. The second scan was done the traditional way,
with patients taken off hormone suppression medication temporarily
so the thyroid gland was reactivated to absorb the radioiodine on its own.
The scans using the artificial compound turned out to be as good or
better than the traditional method in 109 patients, or 86 percent of the
study group. Of these, 106 had equal scans and three had better scans.
The results also indicated that the patients had a better quality of
life when given the artificial compound coupled with their medication than
when they were taken off medication. The quality of life score measured
the severity of hypothyroid symptoms, including depression, weight gain,
fatigue, muscle weakness, cramps and dry skin.
Traditional post-operative treatment of thyroid cancer patients includes
a long period of taking medication to suppress production of thyroid-stimulating
hormone, which may fuel tumor growth, and periodic radioiodine scans to
make sure the cancer has not returned.
Going on and off hormone-suppression therapy typically causes unpleasant
symptoms that put stress on the body, including strain on the heart, as
patients' thyroid hormone level falls.
"It is gratifying to see these results. We anticipate that patients
will no longer have to endure the debilitating side effects of hypothyroidism
in order to have sensitive testing to detect thyroid cancer," noted Bruce
D. Weintraub, M.D., of the University of Maryland Medical Center.
The study was published in the Sept. 25, 1997 issue of The New England
Journal of Medicine.
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