Epidemiology of pituitary pars intermedia dysfunction: A systematic literature review of clinical presentation, disease prevalence and risk factors.
Authors: Ireland J L, McGowan C M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Epidemiology of Pituitary Pars Intermedia Dysfunction Pituitary pars intermedia dysfunction (PPID) represents an age-related degenerative condition of dopaminergic neurones with considerable clinical significance in equine practice, yet robust epidemiological data have remained sparse. Ireland and McGowan's systematic review synthesised 29 publications from 358 initially identified papers, examining clinical presentation, disease prevalence and risk factors, though meta-analysis was precluded by substantial methodological heterogeneity across studies. The most consistent clinical manifestations were hypertrichosis and abnormal hair coat changes, laminitis, and epaxial muscle wastage or atrophy—all demonstrating increased prevalence with advancing age—with robust prevalence estimates of 21.2% in horses and ponies aged ≥15 years and 2.9% across the general equine population. Whilst investigations into breed and sex predispositions yielded equivocal findings, advancing age emerged as the sole definitively established risk factor. For practitioners, this emphasises the importance of maintaining heightened clinical vigilance for characteristic signs in geriatric horses and ponies, particularly those presenting with refractory laminitis or unexplained muscular deterioration, whilst recognising that current evidence does not support routine screening based on breed, sex, or other demographic variables.
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Practical Takeaways
- •Expect PPID in approximately 1 in 5 horses aged 15+ years; clinical suspicion should be high in older animals with hypertrichosis and laminitis
- •Monitor senior horses for hair coat changes and muscle wasting over the epaxial region as early indicators of PPID, regardless of breed or sex
- •Age-related degenerative changes in dopaminergic neurons are inevitable; focus management on early detection and symptom control rather than prevention
Key Findings
- •PPID prevalence is 21.2% in horses and ponies aged ≥15 years and 2.9% in the general equine population
- •Hypertrichosis, hair coat abnormalities, laminitis, and epaxial muscle wastage are the most frequently reported clinical signs
- •Clinical sign prevalence increases with advancing horse age
- •Increasing age is the only significant risk factor identified; breed and sex predispositions remain equivocal