Hormonal, clinical, and survival outcomes in horses and ponies diagnosed with pituitary pars intermedia dysfunction in primary care practice.

Overview

• This study investigated factors that influence hormonal, clinical, and survival outcomes in horses and ponies diagnosed with pituitary pars intermedia dysfunction (PPID) in a primary care setting.
• The research focused on how initial hormone levels, clinical signs, treatment approaches, and owner-related factors affect the recovery and longevity of equids with PPID.

Background

• PPID is a common endocrine disorder in horses and ponies, often affecting older animals, and characterized by dysfunction in the pituitary gland’s pars intermedia region.
• It causes elevated hormone levels, particularly adrenocorticotropic hormone (ACTH), leading to various clinical signs and potentially decreased survival.
• Previous research has lacked comprehensive analysis on which factors best predict hormonal normalization, clinical improvement, and survival in affected equids.

Study Objectives

• To evaluate how initial hormone concentration, clinical symptoms, treatment regimens, and owner-related socio-economic variables influence the outcomes of PPID in horses and ponies.
• Specifically, to identify variables associated with:
  • Normalization of ACTH hormone levels after diagnosis
  • Clinical improvement post-diagnosis
  • Survival time following diagnosis

Methods

• Data was collected retrospectively from medical records of 213 horses and ponies diagnosed with PPID in two university-affiliated primary care practices.
• The study design was an analytical observational cohort study.
• Statistical analyses included:
  • Fisher’s exact tests and Mann-Whitney U tests to identify associations between variables and outcomes.
  • Stepwise backward multivariable logistic regression to find independent predictors of outcomes, reporting odds ratios (OR) with 95% confidence intervals (CI).

Key Findings

• Hormonal normalization (ACTH levels):
  • Lower age at diagnosis increased the likelihood of normalization (OR: 0.90 per year, indicating younger age has better odds).
  • Shorter time intervals between hormonal tests also favored normalization (OR: 0.96 per month).
• Clinical improvement:
  • Moderate body condition scores (BCS between 4 and 6 out of 9) at diagnosis were strongly associated with clinical improvement (OR: 15.07), indicating healthy weight status is important.
  • Higher median household income (MHI) in the owner’s county was independently associated with better clinical improvement outcomes (OR: 1.17 per $1000 increase), suggesting socio-economic factors impact care and recovery.
• Survival after diagnosis:
  • Younger age at diagnosis was positively associated with longer survival (OR: 0.91 per year).
  • Higher MHI was also linked to improved survival chances (OR: 1.04 per $1000 increase).

Interpretation

• Early diagnosis appears critical for better hormone control and survival outcomes in equids with PPID.
• Maintaining a healthy body condition (neither too thin nor overly fat) at diagnosis supports favorable clinical outcomes.
• Frequent monitoring of hormone levels enables faster detection of changes and targeted treatment adjustments.
• Owner-related factors such as financial resources, as approximated by county median income, may affect the level of veterinary care and management possible, influencing both clinical improvement and survival.

Conclusions and Implications

• Management of PPID should prioritize early detection and regular hormonal testing to optimize treatment effectiveness.
• Attention to maintaining balanced body condition may enhance clinical responses.
• Veterinary care providers should recognize the influence of socio-economic factors and work to support all owners in achieving optimal outcomes.
• These findings can guide clinicians in prognosis, client counseling, and tailored therapeutic management strategies for horses and ponies with PPID.