An 18-year-old student is brought to the emergency department due to dizziness and weakness. The patient was studying for final exams with her friends when she suddenly felt dizzy and started having palpitations. She tried to get up but felt weak and had to sit back down. The patient has had several similar episodes in the past 2 months. She lives with her parents and commutes to a nearby college. She has no prior medical conditions. Family history includes diabetes mellitus in her father. The patient reports occasional alcohol use. Temperature is 37 C (98.6 F), blood pressure is 110/70 mm Hg, pulse is 90/min, and respirations are 16/min. There are no orthostatic changes. BMI is 19 kg/m². Physical examination shows no abnormalities. Finger-stick glucose is 48 mg/dL. Symptoms promptly resolve with intravenous dextrose. Serum insulin and C-peptide levels, drawn prior to dextrose administration, are elevated. Which of the following best explains this patient's symptoms?

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11ec25c8_d7c8_ca44_bc81_01a7c6f904a6_MD0003_00 This patient has symptomatic hypoglycemia, and the elevated insulin and C-peptide levels suggest that this is due to excessive endogenous secretion of insulin because C-peptide is cosecreted with endogenous insulin but not present in injectable insulins. Although this could be due to an autonomous insulin-secreting islet cell tumor (ie, insulinoma), such tumors are very rare and usually occur at age >40. Surreptitious use of a sulfonylurea or other insulin secretagogue is much more likely, particularly in a patient with a family member who has diabetes mellitus or other access to prescription medications (eg, pharmacy worker). The diagnosis can be confirmed with a hypoglycemic drug screen. Factitious disorder is characterized by intentional falsification of illness in the absence of external reward (eg, financial compensation, disability benefits). Patients with factitious disorder appear to be motivated by internal factors, such as psychosocial stressors (eg, college workload, final examinations) or desire for validation. A history of major childhood illness or abuse is associated with increased risk, but the etiology is poorly understood. Treatment primarily includes psychotherapy. (Choice A) Binge alcohol drinking can cause hypoglycemia due to depletion of hepatic glycogen, impaired gluconeogenesis, and altered counterregulatory hormone (eg, epinephrine) secretion. However, this patient's elevated insulin and C-peptide levels indicate excessive endogenous insulin secretion as the cause. (Choice B) Patients with factitious disorder may induce hypoglycemia by injecting exogenous insulin. However, exogenous insulin preparations do not contain C-peptide, so levels would be low. (Choices C and D) Phentermine is a centrally acting appetite suppressant that can cause short-term weight loss in patients with obesity. However, reduced caloric intake, whether due to anorexiants or simple dietary restriction, rarely causes severe hypoglycemia because of the induction of multiple counterregulatory factors (ie, glucagon, cortisol, epinephrine, growth hormone). In addition, C-peptide would not be elevated. (Choice E) Self-induced vomiting (eg, due to an eating disorder) can cause dizziness and weakness due to the resulting metabolic derangements (eg, hypovolemia, metabolic alkalosis, hypochloremia) but would not cause increased endogenous insulin secretion. Patients would often have orthostatic hypotension. Educational objective: Factitious disorder is characterized by intentional falsification of illness in the absence of external reward. Patients appear to be motivated by internal factors, such as psychosocial stressors or desire for validation. Patients with factitious disorder may have hypoglycemia due to the surreptitious intake of sulfonylureas or insulin. References: Psychological aspects of factitious disorder. (http://www.ncbi.nlm.nih.gov/pubmed/29489075)

An 18-Year-Old Student Is Brought to the Emergency Department Due