Intended for healthcare professionals

Education And Debate

Thyroid function tests—time for a reassessment

BMJ 2000; 320 doi: (Published 13 May 2000) Cite this as: BMJ 2000;320:1332

Consequences of the TSH

In 1973 Thyroidologists officially endorsed the newly designed TSH
test for thyroid function. Since I was trained prior to this meeting my
clinical knowledge of how to diagnose hypothyroidism seemed
anachronistic. However watching patients with all the symptoms of low
thyroid taking years or decades to show a raised TSH for what was
clinically obvious has been enlightening. Yes, the TSH may eventually rise
but not necessarily. But, treatment of the clinical symptoms has always
been effective regardless of the TSH. Following behind me has been a
generation of medically trained doctors without any knowledge of the art
of diagnosis of hypothyroidism. Current GP's are unable to diagnose any
form of low thyroid condition without a laboratory test.

The TSH test caused the appearance six years later of chronic fatigue
and fibromyalgia. It also lead to a generation of medical students who did
not recognize that chronic fatigue and fibromyalgia are classic symptoms
of low thyroid as are well discussed in the text-books of the 1930s. It
has been my experience, which is the same as that of George Crile's
testbook in 1930 (1), that if diagnose low thyroid early the symptoms of
low thyroid including chronic fatigue and fibromyalgia completely
disappear. But if it is missed for a number of years then the condition is
more difficult to reverse. We now have 27 years with the TSH and many
people have been permanently disabled by the inability and hesitancy of
the current GP's and Endocrinologists to clinically commit themselves to
the diagnosis of hypothyroidism and as discussed below treat adequately.

There is a further difficulty created by the TSH and that is the
treatment of hypothyroidism has been linked to the TSH value. As we know
from Dr. A.D. Toft(2),(See letter of reply) except at extremes there is no
relationship of signs and symptoms to the TSH value. What has been the
point in teaching medical students to follow this test? Moribund patients
are being treated with doses of thyroid which are too low because of the
extreme sensitivity of the TSH to exogenous thyroid hormone. Before the
TSH test arrived, the normal amount of thyroid used by the medical
profession world wide after 80 years of clinical experience was between
200 and 400 micrograms of thyroxine. The current levels dictated by the
TSH value have average about 75 to 100 micrograms. This is 1/3 the dose
which will make a patient feel normal again. Therefore even if the chronic
fatigue patient does have a raised TSH, the treatment has been inadequate.

Thyroid hormone remains one of the safest therapeutic agents that
came out of the 1800's. Aspirin which also came from that era has caused
huge numbers of deaths from overdose whereas thyroid hormone has yet to
record a death from acute overdose. All the scare about osteoporosis was
unfounded. There has not been a documented case of thyroid hormone use
being related to osteoporosis. The hesitancy to use thyroid hormone has
been established and perpetuated by the TSH test.

1. Crille, G. and associates. Diagnosis and Treatment of Diseases of
the Thyroid Gland 1932 Pages 86-100.

2. Toft,A.D. Throtropin:Assay, Secretory Physiology, and Testing of
Regulation. Werner and Ingbar's The Thyroid A fundamental and clinical
text. Sixth Edition Eds. Braverman, L.E., Utiger, R.D. J.B. Lippincott
Company, London, 1991. Page 294

Competing interests: No competing interests

29 May 2000
David M Derry
Former Assistant professor of Pharmacology University of Toronto
305 Goldstream Av. Victoria BC Canada