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Equine Cushing’s Disease (PPID), insulin resistance, and high-NSC feeds are closely linked in a cycle of metabolic dysfunction. Many horse owners notice issues like laminitis, lethargy, coat changes, or abnormal fat distribution, but understanding the underlying hormonal connections is essential for effective management.
This article breaks down how high levels of NSC in the diet, insulin resistance, elevated cortisol, and dopamine suppression are all connected in horses, particularly those at risk of PPID (Cushing’s Disease).
NSC (Non-Structural Carbohydrates) include sugars, starches, and fructans, carbohydrates that are rapidly digested in the small intestine and cause spikes in blood glucose and insulin levels.
ESC = Ethanaol Soluble Carbohydrate (simple sugars including glucose, fructose and sucrose that are digested in the small intestines
WSC = Water Soluble carbohydraes include the simple sugars plus fructans and short chain polysaccharides. Fructans are digested in the hindget.
NSC = Non Structural Carbohydrate = WSC + Starch
Common sources include:
When horses regularly consume high-NSC feeds, their bodies must produce more insulin to move glucose into cells. Over time, tissues become less responsive to insulin, leading to insulin resistance. This means glucose stays in the bloodstream longer, and insulin levels remain elevated, a condition known as equine insulin dysregulation.
Insulin resistance increases the risk of:
Chronic insulin resistance and inflammation from high-NSC feeding can influence the endocrine system. In some horses, this metabolic stress affects the hypothalamic-pituitary-adrenal (HPA) axis, leading to increased output of cortisol—the stress hormone.
Elevated cortisol levels contribute to:
In healthy horses, the dopaminergic neurons in the brain help regulate the pituitary gland, particularly the pars intermedia, which controls hormone output. With age, oxidative stress, or chronic metabolic strain (such as long-term high-NSC diets), these neurons degenerate, reducing dopamine levels. Low dopamine results in the pituitary gland becoming overactive, producing excess ACTH (adrenocorticotropic hormone), which drives up cortisol levels further. This hormonal imbalance is the hallmark of Cushing’s Disease (PPID).
To summarise the cascade:
If your horse is at risk of or already showing signs of Cushing’s Disease or insulin resistance, here’s what you can do:
