WBR0223

Author	[[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Emergency Room
Sub Category	SubCategory::Endocrine
Prompt	[[Prompt::A 45 yr old is brought to the ED by his son. He was in his usual state this morning when he suddenly developed headaches, sweating and loss of consciousness. Physical examination shows a diaphoretic and comatose man. His fingerpick test show glucose of 45mg/dl. He regains consciousness after IV dextrose. He is then admitted to the hospital and recovers well on dextrose insulin infusion. He states that he is stressed out in his work and further investigation shows elevated serum insulin and C-peptide. Plasma insulin antibody is negative. What is the most probable cause for this episode?]]
Answer A	AnswerA::Exogenous insulin
Answer A Explanation	AnswerAExp::'''Incorrect''' : Exogenous insulin administration leads to suppression of endogenous insulin production and hence C-peptide levels would be low.
Answer B	AnswerB::Insulinoma
Answer B Explanation	[[AnswerBExp::Incorrect : Insulinoma is differentiated from sulphonyurea by elevated proinsulin levels. Though in this patient it could not be ruled out, patient history is more suggestive of sulphonylurea abuse.]]
Answer C	AnswerC::Sulphonylurea
Answer C Explanation	[[AnswerCExp::Correct : Sulphonylurea act by depolarization of K+ channels in beta cells and enhance insulin release causing elevated serum insulin and C-peptide levels. Drug abuse should always be considered as a cause in patients undergoing stress of any nature.]]
Answer D	AnswerD::Prolonged fasting
Answer D Explanation	AnswerDExp::'''Incorrect''' : Prolonged fasting results in underproduction of both insulin and C-peptide.
Answer E	AnswerE::Autoimmune hypoglycemia
Answer E Explanation	[[AnswerEExp::Incorrect : Insulin antibodies can produce hypoglycemia by stimulating insulin release at inappropriate times or by having insulin receptor agonist activity. Absence of antibodies rules out this function.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::Insulin is produced by beta cells of pancreas by conversion of pro-insulin into insulin and C-peptide. With appropriate meals (source of glucose, free fatty acids, amino acids) both insulin and C-peptide are secreted in equimolar quantities. The causes of hypoglycemia with increased insulin levels are insulinoma, sulphonylurea and exogenous insulin. Increased insulin and C-peptide is seen in insulinoma and sulphonylurea. Sulphonylurea act by depolarization of K+ channels in beta cells and enhance insulin release. Drug abuse should always be considered as a cause in patients undergoing stress of any nature. Checking urine or plasma levels of sulphonyl urea would be the most appropriate next step. Educational Objective: References: ]]
Approved	Approved::Yes
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