More Information About the
Best Way to Treat Hypothyroidism
From the Endocrine Society’s 84th Annual Meeting
San Francisco, CA
June 19-22, 2002
Escobar-Moreale Study
There exists an ongoing controversy about whether thyroid patients
need both rapidly-acting T3 and long-acting T4 to treat hypothyroidism.
The Endocrine Society’s recent meeting included an important
clinical presentation entitled Controversies in Thyroid Hormone
Replacement, which provided news about new research.
Dr. Hector F. Escobar-Moreale and colleagues from the Molecular
Endocrinology Institute in Madrid, Spain, described research in
which they gave thyroid hormone treatment to rats from which the
thyroid had been removed and all remaining thyroid tissue had been
destroyed with radioactive 131I.
After confirming hypothyroidism, osmotic minipumps were implanted
under the skin for infusion with either T4 alone (in various concentrations),
or several combinations of T4 plus T3. Rats with normal thyroid
function served as controls. Infusion of T4 alone was unable to
restore normal levels of T4 and T3 in plasma and in the thyroid
tissues of the rats. Although both T4 and T3 appeared in tissues,
the various levels were not the same as found in normal rats.
Dr. Escobar-Moreale emphasized that there was more work to be done
to determine the importance of reaching the exact levels of T4 and
T3 found in normal individuals. Rats, for example, normally have
a 6:1 ratio of T4 to T3 in tissues. It is not clear how important
an exact match of normal ratio is in either rats or patients to
correct evidence of hypothyroidism and relieve symptoms.
Bunevicius/Prang Study
Drs. Robertas Bunevicius and Arthur Prang, Jr., from the Institute
of Endocrinology in Kaunas, Lithuania, and the Department of Psychiatry
at the University of North Carolina, Chapel Hill, respectively,
reported on an important follow-up study. They discussed additional
evidence that treatment with T3/T4 combinations seems to improve
mood in comparison with patients who are treated with T4 alone.
In 1999, the group described the results of treating 33 hypothyroid
patients with T4 alone or with a reduced amount of T4 combined with
a small amount of T3. Improvements in mood state, cognitive functioning,
and concentration of sex hormone-binding globulin occurred after
combined treatment. Later, they reported that improvements in psychological
functioning seemed more evident in cancer patients than in patients
with autoimmune thyroiditis. More recently, they studied ten patients
with hypothyroidism following the removal of the thyroid gland for
Graves’ disease. Here, too, the combination of T4 plus T3
seemed to improve mood in comparison to treatment with T4 alone.
Comment
Although these new figures support the original research hypothesis
of Drs. Bunevicius and Prang, those in the audience seemed to agree
that the numbers of patients studied is still too small to be sure
that patients with combination therapy are indeed better off than
those taking T4 alone. One concern is that T3 may cause brief periods
of temporary hyperthyroidism daily, which could have dangerous effects
on the heart, causing heart arrhythmias and possibly even myocardial
infarction, especially in elderly individuals or those with heart
disease.
There is continuing interest in manufacturing a slow-release T3
product which would not cause temporary hyperthyroidism, but in
the meantime, we expect new research and larger clinical studies
to either confirm or refute the opinion of Drs. Bunivicius and Prang.
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