Pituitary Pars Intermedia Dysfunction (PPID), commonly called Cushing's disease, is a progressive neurodegenerative condition of the pituitary gland and the most common endocrine disorder in older horses, affecting an estimated 15–30% of horses over 15 years of age. The disease results from degeneration of the dopaminergic neurons that normally inhibit the pars intermedia region of the pituitary gland. Without this inhibition, the pars intermedia enlarges and overproduces hormones, particularly ACTH and related peptides. Elevated ACTH stimulates excessive cortisol production from the adrenal glands, disrupting metabolism, immune function, and hormonal balance. The hallmark sign is hirsutism — a long, curly coat that fails to shed normally in spring. Other signs include muscle wasting along the topline, a pot-bellied appearance, excessive drinking and urination, chronic infections, delayed wound healing, and susceptibility to [laminitis](/conditions/laminitis-founder). PPID-associated laminitis is one of the most serious consequences. Horses with PPID often develop insulin dysregulation similar to [Equine Metabolic Syndrome](/conditions/equine-metabolic-syndrome), and the two conditions frequently coexist. Diagnosis is confirmed by measuring resting ACTH levels. Seasonal reference ranges must be used as ACTH is naturally higher in autumn. The TRH stimulation test provides greater sensitivity for early cases. Treatment involves daily oral pergolide mesylate (Prascend). Most horses require lifelong treatment with periodic ACTH monitoring and dose adjustments.
Hirsutism (long, curly coat that does not shed); Muscle wasting along the topline; Pot-bellied appearance; Excessive drinking and urination (polydipsia/polyuria); Recurrent or unexplained laminitis; Chronic or recurrent infections (skin, hooves, sinuses); Delayed wound healing; Abnormal fat redistribution; Lethargy and poor performance; Excessive sweating or temperature dysregulation
Pituitary Pars Intermedia Dysfunction (PPID), commonly called Cushing's disease, is a progressive neurodegenerative condition of the pituitary gland and the most common endocrine disorder in older horses, affecting an estimated 15–30% of horses over 15 years of age. The disease results from degeneration of the dopaminergic neurons that normally inhibit the pars intermedia region of the pituitary gland. Without this inhibition, the pars intermedia enlarges and overproduces hormones, particularly ACTH and related peptides. Elevated ACTH stimulates excessive cortisol production from the adrenal glands, disrupting metabolism, immune function, and hormonal balance. The hallmark sign is hirsutism — a long, curly coat that fails to shed normally in spring. Other signs include muscle wasting along the topline, a pot-bellied appearance, excessive drinking and urination, chronic infections, delayed wound healing, and susceptibility to [laminitis](/conditions/laminitis-founder). PPID-associated laminitis is one of the most serious consequences. Horses with PPID often develop insulin dysregulation similar to [Equine Metabolic Syndrome](/conditions/equine-metabolic-syndrome), and the two conditions frequently coexist. Diagnosis is confirmed by measuring resting ACTH levels. Seasonal reference ranges must be used as ACTH is naturally higher in autumn. The TRH stimulation test provides greater sensitivity for early cases. Treatment involves daily oral pergolide mesylate (Prascend). Most horses require lifelong treatment with periodic ACTH monitoring and dose adjustments.
Hirsutism (long, curly coat that does not shed); Muscle wasting along the topline; Pot-bellied appearance; Excessive drinking and urination (polydipsia/polyuria); Recurrent or unexplained laminitis; Chronic or recurrent infections (skin, hooves, sinuses); Delayed wound healing; Abnormal fat redistribution; Lethargy and poor performance; Excessive sweating or temperature dysregulation