Quantitative differences between immunological and receptor binding activities of hGH in pituitary adenomas from...

Human growth hormone (hGH) in the pituitary extracts from patients with acromegaly and normal subjects was measured by radioimmunoassay (RIA) and radioreceptor assay (RRA) using pregnant rabbit liver membrane, and the RRA to RIA ratios of hGH were calculated. The RRA to RIA ratio of hGH for acromegaly was higher than that for normal (0.90 +/- 0.03 vs 0.75 +/- 0.03, p less than 0.01). When the pituitary extracts were gel filtered on Sephadex G-100 column there were three immunoreactive hGH peaks ("pre-big", "big", and "little" hGH); there were no significant differences in gel filtration patterns of hGH between acromegaly and normal. The "little" hGH component (major component) had a higher RRA to RIA ratio than "pre-big" hGH and "big" hGH in both acromegaly and normal. "Little" hGH extracted from acromegaly had a higher RRA to RIA ratio than that from normal (1.14 +/- 0.09 vs 0.93 +/- 0.04, p less than 0.05). These data support the hypothesis that hGH synthesized in acromegaly may be different from normal.