A 62-year-old man comes to the office for a follow-up visit. He recently had episodes of sweating, headache, tremor, and palpitation while working in his backyard; his wife has noticed that he seems confused during these episodes. Medical history is notable for long-standing type 2 diabetes mellitus treated with insulin glargine and glipizide, hypertension, peripheral vascular disease, and hyperlipidemia. The patient also has chronic kidney disease, and his renal function has declined significantly over the past 2 years despite optimal glycemic control. Which of the following is most likely responsible for this patient's symptoms?
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This patient is likely experiencing recurrent hypoglycemia, presenting with both neurogenic (eg, sweating, tremor, palpitation due to autonomic activation) and neuroglycopenic (eg, confusion, impaired consciousness due to inadequate CNS glucose supply) symptoms. Hypoglycemia generally occurs when circulating insulin levels are excessive for the associated glucose levels.
As blood glucose levels fall during activity or fasting, insulin secretion normally decreases. At the same time, the production of counterregulatory hormones (eg, glucagon) increases to stimulate glycogenolysis and gluconeogenesis in the liver. However, patients taking exogenous insulin are vulnerable to exercise-induced hypoglycemia because insulin continues to be released from the injection site despite falling glucose levels. In addition, strenuous exertion may cause changes in skin perfusion that can lead to increased insulin absorption.
Patients with chronic kidney disease are at increased risk of hypoglycemia due to delayed clearance of insulin by the kidneys. These patients often also have additional factors, such as altered nutrition and autonomic dysfunction, that can delay the normal physiologic compensation.
(Choice A) Patients with diabetes and coronary artery disease may experience atypical anginal symptoms such as fatigue, dyspnea, and nausea. However, this patient's mental confusion is more consistent with the neuroglycopenic effects of hypoglycemia.
(Choice B) Pheochromocytoma is an uncommon catecholamine-secreting tumor that presents with headache, palpitations, diaphoresis, and severe hypertension. However, confusion is less typical and more characteristic of hypoglycemia.
(Choices D and G) Orthostatic hypotension or a vasovagal reaction would cause symptoms of presyncope (eg, light-headedness, darkening of vision) or syncope. Tremor is also uncommon.
(Choice E) Panic attacks can present with tachycardia and diaphoresis, but confusion is atypical. In addition, working in the yard is not a common trigger for panic attacks.
(Choice F) Hyperthyroidism can cause tachycardia and sweating, but symptoms are typically chronic rather than episodic and are often associated with goiter.
Educational objective:
Patients taking exogenous insulin for diabetes are vulnerable to exercise-induced hypoglycemia because insulin continues to be released from the injection site despite falling glucose levels. Patients with chronic kidney disease are at increased risk due to delayed clearance of insulin by the kidneys.