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Alpha subunit

Category Biochemistry
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 & container 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