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Thyroid-Stimulating Hormone

TSH Thyrotropin
Serum (SST) mIU/L

About this test

Pituitary glycoprotein that regulates thyroid hormone synthesis and release. Most sensitive test for thyroid dysfunction; abnormal TSH should be followed by Free T4 (and Free T3 if TSH low).

Reference Ranges

Sex Age Range Notes
All 0–1 yrs 1 – 10 Neonatal (first days higher; confirm with local ranges)
All ≥ 18 yrs 0.4 – 4 Adult; targets vary in pregnancy and in elderly

Clinical Interpretation

Low / Decreased
Low TSH — hyperthyroidism (primary), exogenous thyroid hormone, central hypothyroidism (TSH may be inappropriately normal).
High / Increased
Elevated TSH — primary hypothyroidism, subclinical hypothyroidism, TSH-secreting pituitary tumour (rare — check FT4).

Related Tests

Free T4 Free T3
Specimen
Serum (SST)
Reporting Unit
mIU/L
Category
⚗️ Endocrinology

⚠ Clinical Note
Reference ranges are indicative. Always interpret results in the context of the individual patient and local laboratory reference intervals, which may vary.