An enzyme-linked immunoadsorbent assay for human pituitary glycoprotein free alpha-subunit: evaluation and initial experience in patients with pituitary disease.
An enzyme-linked immunoadsorbent assay (ELISA) for measuring human pituitary glycoprotein free alpha-subunit is described. Pituitary tumours may secrete glycoprotein hormones, their free subunits (alpha, beta) or a combination of these. Non-functioning adenomas often secrete free alpha-subunit. Assays for free alpha-subunit have previously used radioimmunoassay or immunoradiometric principles. Some of these methods are time-consuming and lack specificity and sensitivity. In order to overcome these problems, we have developed a two-site ELISA for alpha-subunit which uses a monoclonal antibody to alpha-subunit as the capture antibody to provide greater specificity. An affinity-purified polyclonal anti alpha-subunit conjugated to alkaline phosphatase was the signal antibody. Detection and quantification were based on phenolphthalein monophosphate conversion to phenolphthalein. The ELISA specifically measured glycoprotein free alpha-subunit in serum or plasma, discriminating between alpha-subunit and the intact glycoprotein hormones. The assay can be completed in 4 h. The assay sensitivity was 0.03 micrograms/l, and a normal range of 0.05 to 0.22 micrograms/l was established. In a retrospective study, elevated circulating glycoprotein alpha-subunit was detected in 22% of patients with non-functioning pituitary tumours previously treated with surgery and/or radiotherapy.
Anyaoku
V N
VN
Unit of Metabolic Medicine, St Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, U.K.
Wood
D F
DF
Pavlou
R
R
Williams
P
P
Tan
K
K
Fidler
S
S
Johnston
D G
DG
D000293:Adolescent; D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005069:Evaluation Studies as Topic; D005260:Female; D015292:Glycoprotein Hormones, alpha Subunit / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000097:blood; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
D015292:Glycoprotein Hormones, alpha Subunit