Synonyms

Thyroid stimulating hormone

Clinical Indications

TSH secretion is regulated by negative feedback from serum free thyroid hormone levels. The serum TSH response to change in free T4 is logarithmic; a twofold change in free T4 induces inverse 10-100 fold changes in TSH. Thus, this negative amplified feedback as the serum T4 increases or decreases, makes TSH a sensitive marker of thyroid function which can become abnormal before there is a diagnostic change in free T4. 

Part of Profile

Thyroid Function Tests

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's)

Availability

On request.

Specific Criteria

None

Turnaround Time

Same Day (Monday to Friday)

Specimen

Serum

Volume

0.5 ml

Container

Yellow top (SST) tube

Collection

No specific collection conditions

Causes for Rejection

Unlabelled sample

Reference Range

0.4 to 5.0 mU/L. Neonates may have levels up to 20 mU/L which decrease to normal by 6 weeks of age.