In the latest Case Record of the Massachusetts General Hospital, a 34-year-old woman, 2.5 months post partum, was admitted to the hospital because of episodic paresthesias and altered mental status, with amnesia for the events. During one episode, hypoglycemia was noted. A diagnostic test was performed.
The differential diagnosis of altered mental status in the postpartum period is broad and includes common disorders such as infections, electrolyte abnormalities, drugs, and diseases of the thyroid, kidneys, or liver. Rare causes, like porphyria and paraneoplastic syndromes, as well as conditions that are specific to the peripartum state, such as cardiomyopathy, eclampsia, and Sheehan’s syndrome, may also be considered.
• What is Whipple’s triad?
Whipple’s triad includes symptoms of hypoglycemia, a low glucose level at the time of symptoms, and resolution of symptoms after correction of hypoglycemia. It is a critical first step in the diagnosis of clinically significant hypoglycemia.
• What are typical symptoms of hypoglycemia?
Hypoglycemic symptoms are described as either autonomic or neuroglycopenic. Autonomic symptoms include intermittent anxiety, sweating, tremulousness, tingling, and paresthesias. Neuroglycopenic symptoms, often seen later, include drowsiness, fatigue, impaired concentration, confusion, amnesia, abnormal behavior, difficulty speaking, and unresponsiveness.
Morning Report Questions
Q: What is the best way to determine the cause of hypoglycemia?
A: The best way to determine the cause of clinically significant hypoglycemia is a supervised 72-hour fast. Concurrent with plasma glucose, the levels of ketones, insulin, C-peptide, and proinsulin should be measured, and a screen for oral hypoglycemic agents should be undertaken if hypoglycemia develops. At the end of the fast, serial measurements of glucose levels obtained after the administration of glucagon can help determine the degree of glycogen storage, which is an insulin-mediated process. The fasting study is useful in distinguishing the causes of ketotic hypoglycemia (+(beta)-hydroxybutyrate) from those caused by an insulin-like effect. Examples of nonketotic causes of hypoglycemia include insulinomas, factitious or felonious administration of hypoglycemic agents, or autoantibodies against insulin or its receptor, while examples of ketotic causes include excessive exercise or prolonged fasting. Factitious or felonious administration of insulin would result in low C-peptide levels, whereas endogenous hyperinsulinemia would be accompanied by a very high C-peptide level. Measuring proinsulin levels and screening for the presence of hypoglycemic agents would help distinguish an insulinoma from secretagogue-induced insulin release.
Q: How is glucose homeostasis affected by pregnancy and lactation?
A: Lactation can cause the increased production of ketones, which can serve as an alternative fuel for the brain during hypoglycemia. Suppression of insulin secretion as circulating glucose levels drop below 80 mg per deciliter results in decreased glucose clearance from the circulation, increased endogenous glucose production through glycogenolysis and gluconeogenesis, and increased ketogenesis. Human breast milk contains approximately 50% more lactose than cow’s milk, and approximately 50 g of glucose is incorporated into breast milk per day. This increased use of glucose lowers circulating glucose levels and suppresses insulin secretion, causing increased ketogenesis, and results in lower insulin requirements for women with diabetes who are lactating. There is a relative increased insulin resistance in late pregnancy contrasted with increased postpartum insulin sensitivity.