Question

A 44-year-old woman is referred to a hospital because of occasional headache accompanied by irritability, confusion, sweating, and hunger. She states that symptoms appeared approximately 3 months ago; they frequently tend to appear early in the morning before breakfast or between meals. On one occasion, during the crisis period, a decreased blood glucose level (55 mg/dL) was detected despite the fact that she consumes a diet rich in glucose. She admits to excessive abuse of alcohol, and she occasionally used aspirin for headaches up to 6 days before admission. Her medical records suggest she was previously treated as a psychopath who was prone to malingering. The patient herself confirms that she was haloperidol-treated for more than 1 year, but she discontinued haloperidol use 2 weeks ago.

Her general physical findings are unremarkable. Routine laboratory tests taken on admission reveal no abnormalities. During echosonographic examination of abdomen, no abnormalities were noted. Fasting test was attempted, but it had to be discontinued due to a fall in blood glucose level from baseline value of 75 to 33 mg/dL 8 hours later. It required intravenous glucose administration and termination of the test. Laboratory analyses taken at the time of test termination also revealed elevated serum insulin (9 uU/ml), elevated serum proinsulin (6.3 pmol/l), and elevated C peptide (0.3 mmol/ml) levels. Insulin receptor antibodies are not present in the patient's serum, and sulfonylurea is absent in the patient's sera and urine.

What disorder is the most likely cause of patient's hypoglycemia?

Intake of aspirin
2. Chronic alcoholism
3. Insulin-producing tumor
4. Deliberate insulin intake
5. Haloperidol therapy

Answer 1

The patient's symptoms and test results, particularly the elevated levels of serum insulin and C peptide without external insulin indicators, point to an insulin-producing tumor as the most likely cause of her hypoglycemia.

Step-by-step explanation:

The most likely cause of the patient's hypoglycemia is an insulin-producing tumor. The clues leading to this diagnosis are the elevated serum insulin, elevated serum proinsulin, and elevated C peptide levels with no evidence of exogenous insulin intake (since insulin receptor antibodies and sulfonylurea were absent). This condition, known as Hyperinsulinism, is often caused by tumors of the β-cells of the pancreas, which can result in episodic hypoglycemia.

Factors like chronic alcoholism, intake of aspirin, and haloperidol therapy can affect blood glucose levels, but they do not typically cause the elevated insulin and C peptide levels seen in this patient. Meanwhile, deliberate insulin intake would generally be detected by the presence of insulin antibodies or sulfonylurea compounds in the blood and urine, which were not found. Therefore, the evidence suggests that the hypoglycemia is due to the oversecretion of insulin by a tumor rather than other causes listed.