Thyroid Stimulating Hormone, Serum

Overview
Department	Biochemistry
Test Code	PTSH
Synonyms	Thyroid Stimulating Hormone hTSH Ultrasensitive TSH II Thyrotropin
Test Availability	Monday - Sunday, testing routinely available out of hours
Turnaround Time	1 day
Stability – Add test	5 days
Specimen Requirements
Specimen Type	Serum Plasma
Preferred	6 mL Red-Top
Acceptable	6 mL SST Yellow-Top or 4 mL Li-Hep Green-Top
Unacceptable
Specimen Transportation
Paediatric Requirements	2 full Li-Hep Microtainer
Aliquot Requirements
Sample Type	Serum
Preferred Volume	1 mL
Minimum Volume	0.3 mL
Aliquot Transportation
Clinical Information
Reference Intervals	0.4 - 4.0 mIU/L
Test Method	Ci8200 analyser
Advanced Notice	Not required
Patient Preparation	Not required
Comments
A TSH will be performed automatically if Free T4 is less than 10 pmol/L.   A normal TSH result excludes thyrotoxicosis in 99% of cases.   A normal TSH coupled with a raised Free T4 is suggestive of Euthyroid Hyperthyroxinemia due to illness, drugs or protein binding abnormalities.   A TSH result of less than 0.3 mIU/L is consistent with Thyroid Autonomy (eg. Goitre), hyperthyroidism or Thyroxine treatment.   TSH may be suppressed in otherwise euthyroid patients in cases of non-thyroidal illness, first trimester pregnancy, goitre, thyroid autonomy and after major surgery. Heterophile antibodies in the serum of certain individuals regularly exposed to animals or who have been treated with animal serum products are known to cause interference with immuno assays.