An insulinoma is a rare type of tumor that grows from part of the pancreas that makes insulin. Insulin is a hormone your body makes to control the level of sugar in the body. When these tumors show up, they release insulin when sugar isn’t present in your blood, which can send your sugar levels plummeting at the wrong time. They can be hard to find because the symptoms they cause are found in many other, more common diseases. While special imaging studies like CT scans or MRIs can find them, they’re often small and can be easily missed.