Adrenal gland disease is the most common serious illness in ferrets in North America, largely attributable to early spay-neuter practices that can be prevented through hormonal implants.
Ferret adrenal disease is a largely iatrogenic welfare problem — caused by veterinary and commercial breeding practices that became standard in North America. Early spay-neuter at 4 to 6 weeks of age suppresses sex hormone production, leading the adrenal glands to compensate by producing excess sex hormones themselves, eventually causing adrenal tumors. European ferrets, where different breeding and management practices prevail, have far lower adrenal disease rates. Welfare improvements require shifting to hormonal management with deslorelin implants rather than surgical neutering, which addresses the behavioral reasons for neutering (odor, aggression) without the adrenal consequences. This is a case where veterinary practice change has major welfare implications.