LIPID-METABOLISM IN HORSES WITH HYPERADRENOCORTICISM

Lipid metabolism was studied in 21 horses with hyperadrenocorticism. T o be included in the study, horses had to have histologic evidence of a pars intermedia adenoma found at necropsy (n = 9), a baseline ACTH c oncentration greater than 400 pg/ml (n = 6), or a plasma cortisol conc entration 2 hours after Iv administration of 25 IU of ACTH greater tha n 413 nmol/L (n = 16). Mean +/- so baseline plasma cortisol concentrat ion was 338 +/- 261 nmol/L (n = 20), mean +/- so plasma insulin concen tration was 97 +/- 54 mu U/ml (n = 15), mean I so plasma beta-hydroxyb utyrate concentration was 1.8 +/- 1.2 mg/dl (n = 21), and mean +/- so plasma nonesterified fatty acids concentration was 6.2 +/- 6.4 mg/dl ( n = 21). None of the horses had hyperlipemia. Compared with clinically normal horses, horses with hyperadrenacorticism had increased lipolys is and increased ketogenesis. II was concluded that cortisol cannot be the sole factor contributing to insulin resistance in ho uses with hy peradrenocorticism.