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A new study found that 13 million Americans may
be unaware of and undiagnosed for their thyroid conditions and that more
widespread thyroid testing is needed. This number is double the previously
suspected level of undiagnosed cases in the United States. The study was
funded by thyroid drug Synthroid's manufacturer, Knoll Pharmaceutical
Co.
The study, known as the Colorado Thyroid Disease
Prevalence Study, set out to determine how common abnormal thyroid function
actually is, and to look at the relationship between abnormal thyroid
function, cholesterol levels, and thyroid symptoms. The researchers studied
25,862 participants at the Colorado statewide health fair in 1995. Among
patients not taking thyroid medication, 8.9 percent were hypothyroid and
1.1 percent were hyperthyroid. This indicates 9.9 percent of the population
had a thyroid abnormality that had most likely gone unrecognized. These
figures suggest that nationally, there may be 13 million Americans with
an undiagnosed thyroid condition.
The study also found that even a slight decrease
in thyroid function -- what is sometimes referred to as "subclinical"
or low-level hypothyroidism -- may raise cholesterol levels. These findings
are consistent with what was reported on by the American
Association of Clinical Endocrinologists survey regarding cholesterol
and thyroid disease in January of 2000. That study found that as many
as ten percent of the 98 million Americans with high cholesterol levels
may not know that their cholesterol is elevated due to undiagnosed thyroid
problems.
The thyroid/heart disease/cholesterol linkage was
further confirmed in the February
15, 2000 Annals of Internal Medicine's publication of the Rotterdam Study
results. The Rotterdam study found that older women with subclinical
hypothyroidism were almost twice as likely as women without this condition
to have blockages in the aorta, and were also twice as likely to have
had heart attacks.
The thyroid is a butterfly-shaped gland that wraps
around the windpipe, behind the "Adam's Apple" area of the neck. The hormones
produced by the gland are essential to stimulating metabolism, growth,
and the body's capacity to process calories. An underactive thyroid --
hypothyroidism -- affects more women than men, and the risk increases
with age for both men and women. The symptoms of hypothyroidism include
fatigue, depression, weight gain, hair loss, muscle and joint pains, and
many other chronic and debilitating symptoms. Low thyroid can also be
linked to increased levels of LDL -- "bad" cholesterol -- and risk of
heart disease.
The Colorado Thyroid Disease Prevalence Study found,
not surprisingly, that as thyroid function declined, patients reported
more symptoms such as hoarse voice, constipation, feeling tired, puffy
eyes, muscle cramps, slower thinking, among others. But there wasn't a
clear-cut linkage between the proportion and type of symptoms reported,
and the level of thyroid failure, and no one individual symptom was a
clear indicator of thyroid failure.
The link between all stages of hypothyroidism and
cardiovascular health, and the vague correlation between symptoms and
disease state, points to the need for more widespread thyroid stimulating
hormone (TSH) testing and more aggressive treatment, especially for subclinical
patients.
Is This Revised Estimate of 13 Million Still
Too Low?
While the Colorado Study has effectively doubled
the estimated percentage of the population believed to be suffering from
undiagnosed hypothyroidism, some doctors believe that relying on the TSH
normal range as the only way to define hypothyroidism may mean that still
more millions are hypothyroid, but undiagnosed and overlooked due to rigid
interpretation of bloodtest results and a need to reevaluate the TSH normal
range.
The key thing is of course that what doctors are
always told is that TSH is the test that gives us a yes or no answer.
And, in fact, I think that's fundamentally wrong. The pituitary TSH is
controlled not just by how much T4 and T3 is in circulation, but T4 is
getting converted to T3 at the pituitary level. Excess T3 generated at
the pituitary level can falsely suppress TSH.
Many people may be suffering from minute imbalances
that have not yet resulted in abnormal blood tests. If we included people
with low-grade hypothyroidism whose blood tests are normal, the frequency
of hypothyroidism would no doubt exceed 10 percent of the population.
What is of special concern, though, is that many people whose test results
are dismissed as normal could continue to have symptoms of an underactive
thyroid. Their moods, emotions, and overall well-being are affected by
this imbalance, yet they are not receiving the care they need to get to
the root of their problems....Even if the TSH level is in the lower segment
of the normal range, a person may still be suffering from low-grade hypothyroidism.
What are the Implications for the Public?
This study, the largest to date that has looked
at the prevalence of thyroid disease, has some important implications
for the public.
The estimated 10% of the population -- double the
number previous thought -- that is suffering from undiagnosed hypothyroidism
points to an urgent need for doctors to become better educated about and
more proactive in testing for thyroid disease. Patients also need to become
more informed, and insist on thyroid testing when doctors or HMO's are
reluctant.
The researchers felt that a careful evaluation of
patients' symptoms should be an important part in the diagnosis of hypothyroidism,
and the existence of several symptoms in tandem should be a signal to
test for thyroid problems. This is a change in focus, in which doctors
have indicated that most patients would not even experience symptoms at
subclinically hypothyroid TSH levels. It is hoped that this realization
that the symptoms -- and negative health consequences such as higher cholesterol
-- of subclinical hypothyroidism warrant that the warning symptoms be
taken more seriously, and not dismissed in the catchall "stressed, depressed,
PMS'd or pre-menopausal" non-diagnosis that many thyroid patients have
for years before they are actually diagnosed.
Among patients taking thyroid medication, only 60%
were within the normal range of TSH. The fact that forty percent of patients,
a number that translates to millions of Americans, are already taking
thyroid hormone and being treated by a doctor but are still not in TSH
range is of great concern. Not only does this show the need for more frequent
monitoring and adjustment of dosages -- versus the typical doctor's recommendation
of maximum yearly testing -- but may in fact suggest that there are serious
inadequacies in the current therapies, which primarily almost solely on
synthetic thyroid hormone replacement known as levothyroxine (brandnames
Synthroid, Levoxyl, Levothyroid, Eltroxin).
The inadequacy of the standard therapy in relieving
symptoms was addressed in February of 1999 when the February 11, 1999
New England Journal of Medicine published a landmark T3
Thyroid Drug Study that found that the majority of patients studied
felt better on a combination of two drugs, including levothyroxine (T4)
and T3, and NOT solely levothyroxine/T4 (i.e., Synthroid or Levoxyl) alone.
The addition of T3 helped relieve depression, brain fog, fatigue and other
symptoms.
Results May Aid Synthroid's Stepped-Up Sales
Efforts
These study findings come shortly after an announcement
by Knoll Pharmaceutical's parent company, BASF, indicating that they plan
for their pharmaceutical activities to achieve a 15 to 20 percent return
on sales in the upcoming year. Eggert Voscherau, a member f BASF's Board
of Executive Directors with oversight for the company's Health & Nutrition
segment, has said:
"We have set this return target as our priority,
and we intend to achieve it by rapidly developing and marketing new drugs,
consistently exploiting the potential of our drugs now on the market and
increasing the focus of our activities."
Part of this effort is BASF Pharma's plans to implement
targeted campaigns to fully take advantage of the market potential for
some of its drugs, such as Synthroid.
How much more of the market Synthroid intends to
capture, or how much more they plan to charge in order to increase their
return, is a question that patients should seriously examine. Synthroid
is already the number two drug sold in the U.S., has an estimated 85 percent
of all the thyroid hormone market in the U.S.. Synthroid is also currently
embroiled in what appear to be the last stages of a class
action lawsuit. This suit, which patients can join until March 10,
2000, is based on the company's alleged suppression of research results
that showed that Synthroid was not superior to its competitive brandname
levothyroxine products, and was thus not entitled to charge as much as
two to three times the competitor's prices.
Archives of Internal Medicine
2000;160:526-534
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