A sensitive double antibody radioimmunoassay for Human Growth hormone (HGH): levels of serum HGH following rapid tolbutamide infusion

Summary A double antibody radio-immunoassay for human growth hormone is described. — The assay can detect 0.0625 mg HGH/ml serum and has good reproducibility. It was found that: 1. a highly pure labelled hormone; 2. a specific and very potent guinea pig antihuman growth hormone antibody; and 3. at least five days of incubation for the first reaction were necessary to achieve this accuracy and sensitivity. -Porcine and rat growth hormone, sera from cow, guinea pig, rabbit, mouse, and toad fish did not react with the guinea pig anti-HGH serum used in the assay. — In four patients after hypophysectomy, HGH concentrations disappeared almost completely, and in another patient no rise of the hormone was seen during an IV insulin tolerance test.-Undiluted human serum appears to produce falsely high levels of HGH. — Normal males exhibited fasting HGH levels from 0 –2.2 mg/ml (mean 0.8 mg/ml). Females ranged from 0.6–15.0 mg/ml (mean 5.1 mg/ml) and 15 acromegalics from 8.0–103.0mg/ml (mean 31.2 mg/ml). — During a rapid tolbutamide tolerance test, serum HGH rose between 2.5- and 82-fold over the fasting levels within 10 to 70 minutes following the glucose nadir.Performed in part during a postdoctoral fellowship Stiftung Volkswagenwerk, Germany.