Thyroid Function Tests: TSH and Free T4
Assessment Stage: Baseline Assessment
Included in Future Health Assessment: Yes
Partner: DHM Pathology
Provider: DHM Pathology
Approximate Cost: Medicare where eligible
What is it?
Thyroid function testing assesses whether the thyroid gland is producing an appropriate amount of thyroid hormone.
The main tests are:
Thyroid-Stimulating Hormone (TSH)
Free Thyroxine (Free T4)
TSH is produced by the pituitary gland and signals the thyroid to make hormone. T4 is the main hormone produced by the thyroid and is converted in the body into the more active hormone T3. (Healthdirect)
What does it measure?
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Reflects the pituitary gland's signal to the thyroid.
High TSH may suggest an underactive thyroid.
Low TSH may suggest an overactive thyroid or excessive thyroid replacement.
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Measures circulating unbound thyroxine available to body tissues.
Free T4 is commonly added when:
TSH is abnormal
Pituitary disease is suspected
Thyroid treatment is being monitored
Pregnancy or other specific clinical circumstances apply
Why is it important?
Thyroid dysfunction can affect:
Energy
Weight
Heart rhythm
Cholesterol
Mood
Cognition
Bowel function
Temperature tolerance
Bone health
Menstrual function
Both overactive and underactive thyroid disease may develop gradually.
Who may benefit?
Testing is particularly relevant for people with:
Fatigue
Unexplained weight change
Palpitations
Heat or cold intolerance
Constipation
Tremor
Menstrual disturbance
High cholesterol
Family history of thyroid disease
Known autoimmune disease
Thyroid medication use
What happens during the test?
A routine blood sample is collected.
TSH is generally measured first, with Free T4 added automatically or clinically requested depending on the result and indication.
Preparation
No fasting is usually required.
Tell your clinician about:
Thyroid medication
Amiodarone
Lithium
Biotin supplements
Pregnancy
Recent severe illness
Biotin can interfere with some thyroid assays and may need to be withheld according to laboratory advice.
Advantages
Simple blood test
Highly validated
Detects common treatable endocrine disorders
Useful for treatment monitoring
Limitations
Acute illness can temporarily alter results.
Medications and supplements can interfere.
Symptoms are not always explained by thyroid function.
Free T3 is not routinely required for standard screening.
How Future Health uses this investigation
TSH and Free T4 are interpreted alongside:
Symptoms
Medication use
Lipids
Heart rhythm
Body composition
Menopause status
Previous thyroid results
Future Health Summary
TSH and Free T4 provide a reliable assessment of thyroid function and can identify treatable causes of fatigue, metabolic change, heart-rhythm disturbance and reduced wellbeing.