05/16/2025
There are 3 forms of laminitis, and as they are quite different it is important that we are clear which form we are talking about.
Most laminitis (around 90%) is HAL - Hyperinsulinemia-Associated Laminitis - due to high levels of insulin in the blood (hyperinsulinemia), usually after eating sugar and starch. The horse or pony will have (or have had) insulin dysregulation (ID). This is the form of laminitis associated with eating lush spring grass, being overweight, not getting much exercise, being a native pony breed...
HAL has previously been called pasture associated laminitis and endocrinopathic laminitis.
HAL is about insulin, not inflammation - the high concentrations of insulin in the blood act on IGF1 receptors in the feet causing the lamellae to stretch and become dysregulated and weak, which can lead to the pedal bone becoming misaligned with the hoof capsule under the horse's weight/movement. Treatment/management involves bringing insulin levels down quickly by keeping the sugar and starch content of the diet low, and (as with all laminitis cases) supporting and realigning the feet. SGLT2 inhibitor drugs are being used to quickly lower insulin in horses with acute laminitis, but side effects have been reported and use should be kept to a minimum with blood and clinical signs closely monitored.
Note that corticosteroid medications can cause insulin dysregulation and have been used to induce hyperinsulinemia-associated laminitis (Pinnell et al 2023).
The other 10% or so of laminitis cases are either
SRL - sepsis related laminitis, or
SLL - supporting limb laminitis.
Sepsis related laminitis SRL is the inflammatory form of laminitis (that we pretty much thought all laminitis was until it was discovered (only around 15 years ago) that insulin causes most laminitis). SRL develops in horses that are already seriously ill, e.g. with colitis/acute diarrhoea, or infection due to retaining placenta after foaling, and it has been experimentally induced by giving horses huge amounts of starch or oligofructose. Damage in the feet is often sudden and serious, with complete separation of the basement membrane/breakdown of the suspensory apparatus. This form of laminitis has been halted in clinics by continuous cooling of the feet (cryotherapy), and horses with inflammatory illness/SIRS being treated in clinics will often have their feet cooled as a precaution before any clinical signs of laminitis are seen. As well as cryotherapy, the primary disease must be treated, and anti-inflammatory treatment given.
Supporting limb laminitis SLL is very rare and mostly seen in clinics when horses are being treated for fractures or significant leg injuries/infections. Laminitis develops in the leg(s) that are supporting the horse, not so much because the supporting leg(s) are taking more weight than normal, but because reduced movement (reduced limb load cycling) of the supporting leg(s) reduces perfusion of blood in the foot/feet and this damages the lamellae. This is the laminitis of reduced blood flow/ischemia. Research is ongoing into how SLL can be prevented and treated, focusing on how to increase limb load cycling (lifting the supporting foot/feet off the ground) and blood perfusion.
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