Thyroid Stimulating Hormone Test
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for Western Australians
The TSH Test
Thyroid disease is very common. Unfortunately thyroid disease is often poorly diagnosed and
poorly managed. Many Australians are hypothyroid and remain undiagnosed, perhaps for
many years to come.

Thyroid disorders can cause many symptoms which may be misdiagnosed as separate
conditions such as depression, atherosclerosis (increased cholesterol), carpal tunnel
syndrome, sleep apnea, anxiety, hypoglycaemia, infertility, insomnia and so on.  

Once diagnosed, patients may also not receive optimal thyroid hormone replacement therapy
and as a result may continue to suffer unnecessarily. The symptoms experienced by patients
with an underactive thyroid are often treated with further drugs or the patients may be
referred to specialists for their thyroid related problems and they may even have
unnecessary surgery. There are a number of reasons why this occurs and it can be explained
as follows:

Many doctors focus solely on test results, in particular the TSH (thyroid stimulating hormone).
The TSH test is seen as the golden standard for diagnosis and treatment of hypothyroidism
and hyperthyroidism. However the TSH is a hormone released by the pituitary gland in the
brain which controls the thyroid gland, but it doesn’t measure thyroid hormone itself and it can
therefore be a poor measure of thyroid hormone production.

Typically hypothyroidism is diagnosed when the TSH is high. The thyroid gland can become
underactive if the pituitary gland fails to produce enough TSH or if the hypothalamus fails to
produce enough TRH (thyrotropin releasing hormone) as seen in the graph below. These
conditions can cause a low TSH and hypothyroidism (low thyroid hormone levels).
Hypothyroidism cannot be diagnosed with a TSH test if either the pituitary gland or the
hypothalamus is not functioning properly.
What is a normal TSH?

In 2002 the US National Academy of Clinical Biochemists (a panel of international experts)
published a comprehensive set of guidelines for the Laboratory Support for the Diagnosis
and Monitoring of Thyroid Disease. One of the guidelines was to reduce the TSH reference
range to 2.5 mIU/L, because the normal reference range for the TSH, used by laboratories,
was considered too wide. Numerous large studies like the one below, showed that the most
common value for the TSH was 1.25 mIU/L. It was concluded that people who had thyroid
antibodies with a TSH of 4 mIU/L or less, who were included in the study, were in the early
stages of thyroid disease. Laboratories are still using the old range of 0.4 to 4 mIU/L today.

European Journal of Endocrinology, 2000, 143 639-647
Drugs and some conditions that decrease or increase the TSH

Certain conditions can also reduce the TSH and give misleading results, such as in
depression, pregnancy and in euthyroid sick syndrome (non-thyroidal illness) which is seen
in acute or chronic severe illness.

Some of the following drugs/supplements can either increase or decrease the TSH and/or
they may interfere with the absorption of thyroxine;


•        Amiodarone or Propranolol (heart medications)
•        Aspirin
•        Warfarin (blood thinning medications)
•        Hormone replacement therapy (oestrogen)
•        Oral contraceptives
•        Anti-depressants, such as Lithium, SSRIs & tricyclic anti-depressants
•        Anti-psychotics (Seroquel)
•        Metoclopramide
•        Morphine
•        Aminoglutethimide
•        Dopamine
•        Anabolic steroids
•        Somatostatin analogues
•        Non-steroidal anti-inflammatory drugs (NSAIDs)
•        Corticosteroids, anti-inflammatory drugs (Prednisolone, dexamethasone)
•        Anti-viral medications (Ritonavir)
•        Anti-malarial medications (Chloroquine)
•        Drugs used to treat diabetes (insulin)
•        Drugs used to decrease cholesterol Ion-exchange resins (cholestyramine)
•        Drugs used for epilepsy (Phenytoin)
•        Drugs used to treat heart failure (Digoxin)
•        Iron supplements
•        Calcium supplements
•        Some antibiotics (Ciprofloxacin, Rifampicin)

Your pharmacist will have a complete list of drugs which may interfere with thyroxine!

A TSH test alone therefore may miss many cases of hypothyroidism. Measuring thyroid
hormone levels such as free T4 and free T3 in addition to the TSH is therefore
recommended.

Click here for further information on Thyroid Function Tests

Disclaimer  The information provided is for educational purposes only and is not intended to be medical
advice. The contents must not be relied upon in place of advice and treatment from a qualified medical
practitioner. Thyroid WA Support Group Inc. and the author disclaim any liability whatsoever. Copyright ©
Monique Atkinson 2011

Thyroid WA Support Group Inc.  -  ABN  84 263 220 330