Free T4

Clinical Chemistry

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Description

TSH is synthesised in the anterior pituitary following stimulation by TRH (thyrotropin-releasing hormone), which is released by the hypothalamus. TSH then stimulates the thyroid to produce and secrete the thyroid hormones thyroxine (T4) and triiodothyroinine (T3). The thyroid hormones, T4 and T3, are essential for normal growth and development and are involved in many metabolic processes, including stimulation of the basal metabolic rate. T4 and T3 also negatively feedback on the pituitary to decrease TSH production.

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Indications

Suspected thyroid disorders, monitoring treatment of patients with known thyroid disorders, monitoring of patients on amiodarone and lithium therapy, suspected or known pituitary or hypothalamic disorders. Please provide relevant clinical details to ensure correct interpretation and addition of relevant tests.

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Sample Type

Serum, SST/Gel, minimum 2 mL (1 mL separated serum).

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Reference Range

Reference ranges are provided on the report. Alternatively, please contact the laboratory for current ranges.

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Turnaround Time

Within 1 day

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Testing Frequency

As required. Please note that STH uses a TSH-first TFT protocol. Free T4 and Free T3 will be reflexed based on clinical details provided and TSH results. All other cases need to be discussed with the Duty Biochemist during normal working hours.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.