Name:
A 25-Year-Old with Hypoglycemia
Description:
A 25-Year-Old with Hypoglycemia
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Duration:
T00H05M08S
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Upload Date:
2022-02-28T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
♪ (music) ♪
CATHY: Hi, welcome to Harrison's Podclass, where we discuss important concepts in internal medicine. I'm Cathy Handy.
CHARLIE: And I'm Charlie Wiener,
CHARLIE: and we're coming to you from the Johns Hopkins School of Medicine. ♪ (music) ♪
CATHY: Welcome to Episode 47: A 25-Year-Old with Hypoglycemia.
CHARLIE: Okay, here's the question. A 25-year-old healthcare worker is seen for evaluation of recurrent hypoglycemia. She has had several episodes at work over the past year in which she feels shaky, anxious, and sweaty. During these episodes, she has measured her finger-stick glucose, and it is typically 40-55 mg/dL. This has also been confirmed with a plasma glucose level during one episode where her finger stick was 50 mg/dL. She then drinks orange juice and feels better.
CHARLIE: These episodes have not occurred outside the work environment. Aside from oral contraceptives, she takes no medications and is otherwise healthy. Her physical examination is completely normal. What are your thoughts, Cathy?
CATHY: Sounds like the main thing going on here is her hypoglycemia. And she has Whipple's triad, which is 1) Symptoms consistent with hypoglycemia-- this would include the shaky, sweaty, and anxious feeling that she gets. 2) She has a low plasma glucose concentration measured with a more precise method. So, this is important because sometimes you can get pseudo-hypoglycemia with finger sticks. For example, this happens sometimes in scleroderma patients, and the finger-stick glucose measurement isn't always accurate, so you want to confirm with the plasma glucose concentration.
CATHY: The third part of the triad is relief of symptoms after the plasma glucose level is raised. In her case, after drinking a glucose load-- sounds like OJ is her drug of choice-- she gets better. Now, this is obviously not normal, so she would need further workup to figure out why she's having these episodes.
CHARLIE: And that's exactly what the question's going to ask. It says: "Which of the following tests is most likely to demonstrate the underlying cause of her hypoglycemia?" Option A is measurement of IGF-1; option B is measurement of insulin and glucose levels while fasting; option C is measurement of insulin, glucose and C-peptide levels while fasting; option D is measurement of insulin, glucose and C-peptide levels during a symptomatic episode; and option E is measurement of plasma cortisol.
CATHY: Let's think for a moment about the body's regulation of glucose. Because plasma glucose concentrations are maintained within a relatively narrow range, roughly 70-110 mg/dL. Insulin plays a dominant role in this. So, as plasma glucose levels decline within the physiologic range, pancreatic beta cell insulin secretion will also decrease, and that subsequently increases hepatic glycogenolysis and hepatic and renal gluconeogenesis. Low insulin levels also reduce glucose utilization in the peripheral tissues, inducing lipolysis and proteolysis and consequently, releasing gluconeogenic precursors.
CATHY: Thus, a decrease in insulin secretion is the first defense that you have against hypoglycemia.
CHARLIE: So, it sounds like you're going to want to measure the serum insulin then.
CATHY: That's definitely on my list.
CHARLIE: Okay, so based on that, it sounds like you can rule out options A and E right off the bat. So, IGF and plasma cortisol are not the correct answers. Options B, C and D all include glucose levels, which we establish is important also. Tell me about C-peptide and whether or not that's important or why that's important in this case.
CATHY: C-peptide is the connecting peptide that's cleaved from the native proinsulin to produce insulin. Now, it's not present in exogenous forms of insulin. So, if insulin levels are high but C-peptide levels are low, this would suggest that it's exogenous insulin that's causing the hypoglycemia.
CHARLIE: Such as, like someone injecting themselves with insulin?
CATHY: Exactly, but if insulin levels are high and C-peptide levels are high, that means that there's endogenous insulin that would be causing the hypoglycemic episodes. So, this could be from a tumor, for example, or even from someone who is taking sulfonylureas because sulfonylureas stimulate pancreatic insulin secretion.
CHARLIE: When should we measure these values, fasting or during the episode?
CATHY: Yes, thank you, so that's the difference between option C and option D. Now, option D is the one that's correct. You do need these values to be obtained and interpreted during the hypoglycemic episode. So, you would want to draw them all at the same time. You really cannot draw conclusions based on values when the glucose is back up in the normal range.
CHARLIE: Okay, so the teaching point of this case is that when faced with a patient with hypoglycemia, first, you want to demonstrate that they, in fact, do have Whipple's triad, and then you can draw additional labs. Those labs should include a plasma glucose level, an insulin level, and a C-peptide, and it's important that those levels be drawn during the symptomatic episode.
CATHY: And to learn more, you can read about this in Harrison's Endocrinology chapter on hypoglycemia. ♪ (music) ♪