Imperial Collage Healthcare

Alpha subunit

Test Background
The α-subunit is common to TSH, LH, FSH and hCG, while the β-subunit is specific to each hormone. The subunits are synthesised and secreted independently. The α-subunit is consistently elevated in cases of TSH secreting pituitary adenoma and its secretion is autonomous and refractory to the negative feedback of thyroid hormones.

Clinical Indications

  • TSH α-subunit assay is indicated for the differential diagnosis of thyroid hormone resistance and TSH-secreting pituitary adenomas (levels are normal in the former and elevated in the latter)
  • Instances of unexplained hyperthyroidism

Reference Range

See report

Sample Required
Serum (red top)

Sample Volume
0.5 mL

Turnaround Time
Up to 6 weeks

Not currently performed in house; this is a referred test

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