Some pituitary macroadenomas may secrete only alpha subunit (ASU) making this a diagnostically useful test.Decreasing levels following surgery or radiotherapy can be useful in patient management. ASU measurement may also find a use in the differential diagnosis of TSH-secreting pituitary tumour versus thyroid hormone resistance.
The glycoprotein hormones TSH, LH, FSH and HCG are composed of an alpha and beta subunit – the former is common to all these hormones. ASU is normally secreted as the free hormone as well as in combination with the glycoprotein hormone beta subunit.
Serum: Plain red topped tube preferred but can use an SST sample
Please send clinical details including results of other pituitary hormone tests.
Selly Oak Hospital