Thanks to Courtney and Joe for presenting the fascinating endocrine case today! Here are some of the pearls:
- The counterregulatory hormones to insulin include glucagon, epinephrine, cortisol, and growth hormone. Euglycemia in the 70-100 range is maintained by glucagon. When blood glucose is <70, both glucagon and epinephrine are secreted. When blood glucose falls below 60, both cortisol and growth hormone are also secreted.
- Hypoglycemia framework:
- Insulin mediated: Insulinoma, exogenous (insulin, sulfonylurea, meglitinides
- Non-insulin mediated: alcohol, sepsis, hepatic failure, adrenal insufficiency, malnutrition
- Surreptitious/exogenous sulfonylurea intake is indistinguishable from insulinoma without the urine sulfonylurea screen (classic boards question)
- Whipple’s triad for hypoglycemia: 1) Hypoglycemia sx are present 2) low glucose on P7 3) Prompt resolution of sx after glucose ingestion…..ask Mike Cruz for his tetrad =)
- Insulinoma work up includes 72 hour fast, check labs when hypoglycemia occurs including BHB, pro-insulin, C-peptide, plasma insulin, glucose level
- Reason BHB is low with insulinoma: The high insulin levels tell the body that it’s in a fed state, so the body does not break down FFA to produce ketones. This also means that glycogen stores are normal, so when glucagon is given at the end of the fast, the glucose will rise >25 mg/dl. In contrast, if a healthy person goes on a 72 hour fast, he/she will deplete her glycogen stores, and there will be a minimal response to glucagon. BHB levels will be elevated due to starvation and use of ketones as an alternate glucose source.
- Management includes surgical resection when diagnosed with imaging. If surgery not possible, diazoxide (Calcium channel blocker no longer available in the US), octreotide, propranolol, verapamil are some medical therapies that can be tried.
|Plasma Glucose||Serum Insulin||Plasma C-Peptide||Urine sulfonylurea screen|
Dr. Patty Salmon our endocrinology attending shared these two great articles. One is the classic NEJM article on insulinoma and the other are practice guidelines. Thanks!