Effects of proligestone and megestrol on plasma adrenocorticotrophic hormone, insulin and insulin-like growth factor-1 concentrations in cats.

This paper reports changes in adrenocorticotrophic hormone (ACTH), insulin and insulin-like growth factor-1 (IGF-1) concentrations in cats from a previously published study. The cats were given oral megestrol acetate (MA, 5 mg once daily for 14 days), subcutaneous proligestone (PRG, 100 mg on two occasions one week apart) or subcutaneous saline (1 ml as for PRG). In the cats given saline (n = 6), basal ACTH, insulin and IGF-1 did not change significantly throughout the following seven weeks. The cats given MA (n = 7) developed significant suppression of plasma ACTH concentrations and hyperinsulinaemia during treatment and for two to four weeks after MA dosage ceased. In the cats given PRG (n = 7), plasma ACTH concentrations were not significantly altered although three cats had markedly suppressed values for some time after PRG treatment had ceased. Serum insulin concentrations were not significantly altered in the PRG-treated cats. The results suggest PRG may be a preferable alternative to MA in some situations.