Insulinoma is a tumour of the insulin-producing beta cells of the pancreas. Because the tumour cells retain the ability to secrete insulin — often in excess and without the normal regulatory controls — the hallmark of this cancer is dangerously low blood sugar (hypoglycaemia). Affected dogs may show weakness, disorientation, trembling, or even seizures, particularly after fasting or exercise. The symptoms can be intermittent, as insulin release from the tumour may fluctuate. Most insulinomas are malignant, though they tend to be slow-growing. Spread is most commonly to the liver and regional lymph nodes. Surgical removal of the tumour can provide significant benefit, and medical management with dietary changes and medications that counter insulin's effects can help maintain stable blood sugar levels. German Shepherds, Irish Setters, and Golden Retrievers are among the breeds at higher risk.