Validation and application of a radioimmunoassay for ovine growth hormone in the diagnosis of acromegaly in cats.

The validity of an ovine growth hormone (OGH) assay for the detection of feline growth hormone (FGH) was demonstrated by the parallel displacement of radiolabelled OGH by standard concentrations of OGH and serial dilutions of pooled FGH-rich serum. The minimum detectable limit of the assay was 1.67 microg/l. The mean (sd) basal fasting FGH level in 19 non-acromegalic, non-diabetic cats aged two to 16 years was 4.01 (1.38) microg/l (range 1.87 to 6.33); 19 acromegalic cats had significantly higher FGH levels (range 8.45 to 33.2 microg/l). There were no significant differences in the FGH levels measured when aprotinin was added to the samples or when plain serum and serum gel separation tubes were used for blood collection, but the FGH levels were significantly higher when the samples were collected into EDTA. There were also no significant differences between the concentrations of FGH measured in samples in which the separation of the serum and storage had been delayed by 24 hours, or in samples that had been stored for up to four weeks at -20 degrees C.