05/09/2026
With the warmer weather, a few points to consider:
Adipose tissue (fat) functions as an endocrine organ in horses, just as it does in humans.
In both species, white adipose tissue is far more than an energy-storage depot. It actively secretes bioactive molecules called adipokines (and adipocytokines) that act locally or systemically to influence energy balance, appetite, insulin sensitivity, inflammation, and other processes. 
Key similarities
• Leptin: Secreted in proportion to fat mass. Higher body fat → higher circulating leptin. It signals satiety to the brain and is elevated in obese horses.
• Adiponectin: Produced almost exclusively by adipocytes. It improves insulin sensitivity and has anti-inflammatory effects. Levels generally fall as fat mass rises; low adiponectin is linked to insulin dysregulation and higher laminitis risk in horses.
• Other factors: Inflammatory cytokines (e.g., TNF-α, IL-1β, IL-6, CCL2) and other adipokines are produced, especially when adipose tissue becomes dysfunctional in obesity.
• Steroid hormone metabolism: Adipose tissue contains enzymes (such as 11β-HSD1) that locally activate glucocorticoids, influencing metabolism and adipocyte differentiation.
These functions are well-documented in equine research, particularly in the context of obesity and equine metabolic syndrome (EMS). EMS shares parallels with human metabolic syndrome: excess adiposity, insulin dysregulation, chronic low-grade inflammation, and increased risk of related problems (laminitis in horses versus type 2 diabetes/cardiovascular disease in people). 
Notes on differences in knowledge depth
Scientific understanding of the equine adipocyte “secretome” is less complete than in humans or rodents, but the core endocrine role is clearly established. Regional fat depots (e.g., nuchal/cresty neck fat, visceral/peri-renal, retroperitoneal) can differ in activity and inflammatory profile, which is clinically relevant for EMS risk assessment.
In short, the recognition of fat as an endocrine organ applies to horses in the same fundamental way it does to humans, with important implications for managing equine obesity and metabolic health.
Equine metabolic syndrome (EMS) is a common endocrine disorder in horses, ponies, and donkeys. It is defined as a collection of risk factors centered on insulin dysregulation (ID) that greatly increases the risk of hyperinsulinemia-associated laminitis (HAL), the most common form of laminitis in the general equine population (accounting for >90% of cases in many studies). 
EMS is not a single disease but a syndrome arising from the interaction of genetic predisposition and environmental factors (especially diet and management). It is analogous in some ways to human metabolic syndrome, though the primary clinical concern in horses is laminitis rather than cardiovascular disease or type 2 diabetes.
Core Features
• Insulin dysregulation (ID) — the consistent, defining component. This includes any combination of:
• Resting (basal) hyperinsulinemia
• Exaggerated or prolonged insulin response after eating or carbohydrate challenge (postprandial hyperinsulinemia)
• Tissue insulin resistance (peripheral or hepatic)
• Increased adiposity — generalized obesity (body condition score typically ≥7/9) and/or regional adiposity (cresty neck, fat pads over the tailhead/rump, behind the shoulder, prepuce, or mammary gland). Note: Lean phenotypes with regional fat deposits also exist (“lean EMS”).
• Predisposition to laminitis (acute episodes or chronic/subclinical with divergent hoof rings).
• Variable additional findings: altered lipid metabolism (e.g., hypertriglyceridemia), abnormal adipokine levels (high leptin, low adiponectin), and sometimes mild hypertension or reproductive changes in mares.
Obesity is common and exacerbates the problem but is not required for diagnosis—ID is the essential feature. 
Pathophysiology
ID develops through a combination of excessive pancreatic insulin secretion in response to nonstructural carbohydrates (NSCs — sugars and starches), reduced hepatic insulin clearance, and tissue insulin resistance. High circulating insulin is toxic to the digital laminae of the hoof, leading to HAL.
Adipose tissue plays a key role as an endocrine organ (as discussed previously). Dysfunctional fat secretes elevated leptin and pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, CCL2) while producing less adiponectin (an insulin-sensitizing and anti-inflammatory adipokine). This contributes to systemic inflammation, further impairs insulin signaling, and promotes a vicious cycle of worsening ID and adiposity. 
Genetic factors (a “thrifty” or easy-keeper genotype) interact with modern management: high-NSC diets (lush pasture, grain, treats), overfeeding, and insufficient exercise.
Predisposed Groups
Higher risk in ponies, donkeys, miniature horses, and certain horse breeds including Morgans, Arabians, Andalusians/Iberian breeds, Paso Finos, Saddlebreds, and some Warmbloods. Thoroughbreds and Standardbreds are less commonly affected. It typically appears in young-to-middle-aged animals (often 5–15 years), though it can occur at any age and may coexist with pituitary pars intermedia dysfunction (PPID/Cushing’s) in older horses.
Diagnosis
Diagnosis relies on history, physical examination (body condition scoring, cresty neck score, evidence of current or past laminitis), and laboratory confirmation of ID. Visual assessment of obesity alone is insufficient.
Recommended tests (per Equine Endocrinology Group / EEG guidelines):
• Oral sugar test (OST) — preferred dynamic test: measure insulin (and sometimes glucose) after administering corn syrup. Detects exaggerated postprandial insulin responses and is useful for assessing laminitis risk.
• Insulin tolerance test (ITT) — evaluates tissue insulin resistance.
• Resting (basal) insulin and glucose — useful for screening moderate-to-severe cases but less sensitive for mild ID.
• Additional tests may include adiponectin measurement or ruling out concurrent PPID (e.g., ACTH testing) in older animals.
Testing is recommended for at-risk horses, those with unexplained laminitis, before corticosteroid use, or as part of wellness/pre-purchase exams. 
Management and Treatment
The foundation is management, not just medication:
1. Dietary control (most important):
• Strict restriction of NSCs (ideally forage NSC