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) |
| Reference range | See report |
| Sample & container required | Serum (red top) |
| Sample volume | 0.5 mL |
| Turnaround time | Up to 6 weeks |
| Notes | Not currently performed in house; this is a referred test |