12/01/2026
Laminitis is not a primary disease; it is always the secondary outcome of some event, ranging from sepsis, supporting limb laminitis, black walnut shavings, or endocrine disorders -- the latter accounting for the majority of reported cases. The causal agent of endocrinopathic or “insulin-induced” laminitis is insulin. Dietary sugar and starch, obesity, lack of exercise are factors that play a role in insulin regulation but are not the cause. Iron overload disorder (hyperferritinemia) from excessive dietary iron can be associated with insulin resistance and diabetes in humans and many animal species including equines but does not cause insulin resistance or laminitis. *(PMID: 32042647). Genetic makeup is likely the greatest contributor to the development of EMS and PPID. *(PMID: 32534851).
Exercise is by far the best way to maintain normal glucose and insulin dynamics in all animals. In cases where insulin is abnormally high (hyperinsulinemia), controlling the amount of dietary hydrolyzable carbohydrates (simple sugars and starch) responsible for glucose and insulin secretion will help to lower insulin and reduce the risk of laminitis. Hyperinsulinemia can be transient. For example, a healthy horse with normal insulin can graze spring grass or eat a grain meal and can have high serum insulin concentrations that respond normally to the amount of simple sugars and starch in the meal. Within hours, insulin values return to normal. In contrast, an equine with EMS has an even higher insulin response to all meals, even meals with low sugar/starch, and fasting insulin is higher.
There are plenty of sedentary, overweight, grain-fed equines that don’t have EMS. Likewise, there are many older horses that don’t develop PPID. There are many horses with excessive iron in their diets that don’t develop iron overload disorder (IOD; hyperferritinemia). Yes, lack of exercise can lead to increased risk of obesity. Obesity can lead to increased risk of insulin resistance and inflammation of adipose tissue (fat) *(PMID: 36244309), but insulin-induced laminitis is not caused by adipose tissue or systemic inflammation. What is the best predictor of insulin-induced laminitis? Insulin! *(PMID: 35263471).
This is not a matter of semantics – it’s basic physiology. In order for treatments or management to be effective, we must understand the direct cause. In a recent publication, the authors stress the importance of testing for insulin resistance "...in communications about endocrinopathic laminitis, whether in scientific publications, disease awareness initiatives, or continuing education events.” *(PMID: 34958881).
Of course, we shouldn’t ignore the other factors that play important roles in the management of EMS or the treatment of PPID. If able, introduce exercise to encourage weight loss and stimulate glucose uptake, reducing the demand to secrete more insulin. Limit simple sugars and starch in the diet. Analyze forage to identify mineral deficiencies and excesses. Feed a mineral balanced diet to assure a solid nutritional foundation to work from. Keep the focus on insulin as the central cause of endocrinopathic laminitis.
* Those interested in reading the PMID references can go to https://pubmed.ncbi.nlm.nih.gov and enter the PMID number into the search box.
**For more information, download Dr. Kellon’s proceedings “Protein, Iron and Insulin” from the 2021 NO Laminitis! Conference here: https://www.e-junkie.com/i/11jjd. and https://www.ecirhorse.org/proceedings-2013.php
Kathleen M. Gustafson, PhD
President and Research Advisor, ECIR Group Inc,
