Growth hormone, insulin, glucose, cortisol, luteinizing hormone, and diabetes in beagle bitches treated with medroxyprogesterone acetate.

Adult beagle bitches (20 to 101 months old) received medroxyprogesterone acetate (MPA; 75 mg/kg, im) or control vehicle at 3 month intervals. Changes in serum concentrations of GH, insulin and glucose were determined in 18 MPA-treated and 6 of 12 control bitches at 0, 2, 4, 8, 16 and 17-24 months of treatment (Exp. I). GH, LH and cortisol responsiveness to combined im injection of TRH (10 micrograms/kg), GnRH (10 micrograms/kg), and ACTH (5 micrograms/kg) was determined in 9 MPA-treated and 9 control bitches at 17 months of treatment (Exp. II). In Exp. I, serum concentrations of GH at month 2 (2.6 +/- 0.3 micrograms/l), 4 (3.0 +/- 0.3 micrograms/l), 8 (4.0 +/- 1.2 micrograms/l), 16 (8.5 +/- 1.7 micrograms/l), and 17-24 (21.2 +/- 4.1 micrograms/l) of treatment were greater (P less than 0.05) than pretreatment (1.4 +/- 0.07 micrograms/l) and control (1.5 +/- 0.1 microgram/l) levels. The increase in GH at 2 months preceded (N = 4) or coincided (N = 2) with the development of hyperinsulinaemia and insulin resistance in 6 of the 18 treated bitches, two of which became diabetic by 17 months of MPA treatment. GH (24.6 +/- 5.0 vs 11.4 +/- 2.1 micrograms/l) and insulin (308 +/- 77 vs 119 +/- 9 pmol/l) concentrations were greater (P less than 0.05) in older (49 +/- 4 months; N = 12) than in the younger (26 +/- 2 months; N = 6) treated bitches at 17-24 months of MPA treatment. In Exp. II, pretreatment concentrations of GH were increased (9.8 +/- 3.0 vs 1.4 +/- 0.1 micrograms/l, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)