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Diabetes mellitus

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High Yield Notes

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Diabetes mellitus

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USMLE® Step 1 style questions USMLE

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A 68-year-old man comes to the emergency department complaining of shortness of breath. One hour ago, while attending his nephew’s birthday party, the patient suddenly felt chest tightness with dizziness, and he was unable to catch his breath. Medical history includes type 2 diabetes mellitus, hypertension, chronic kidney disease, and chronic obstructive pulmonary disease. Medications include insulin, simvastatin, and lisinopril. He quit smoking 20 years ago. The patient’s temperature is 37.0°C (98.6°F), pulse is 190/min, respirations are 26/min, and blood pressure is 80/50 mmHg. Physical examination reveals the patient to be pale and in mild distress. Lung auscultation demonstrates clear breath sounds bilaterally. ECG shows the following:  


Reproduced from: Wikimedia Commons

Synchronized electrical cardioversion is attempted; however, the patient loses a pulse immediately afterwards. After 10 rounds of cardiopulmonary resuscitation, the patient is pronounced dead. Which of the following processes was the most likely contributor to this patient’s cause of death?  

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Content Reviewers

Rishi Desai, MD, MPH,Samantha McBundy, MFA, CMI

In diabetes mellitus, your body has trouble moving glucose, which is a type of sugar, from your blood into your cells.

This leads to high levels of glucose in your blood and not enough of it in your cells, and remember that your cells need glucose as a source of energy, so not letting the glucose enter means that the cells starve for energy despite having glucose right on their doorstep.

In general, the body controls how much glucose is in the blood relative to how much gets into the cells with two hormones: insulin and glucagon.

Insulin is used to reduce blood glucose levels, and glucagon is used to increase blood glucose levels.

Both of these hormones are produced by clusters of cells in the pancreas called islets of Langerhans.

Insulin is secreted by beta cells in the center of the islets, and glucagon is secreted by alpha cells in the periphery of the islets.

Insulin reduces the amount of glucose in the blood by binding to insulin receptors embedded in the cell membrane of various insulin-responsive tissues like muscle cells and adipose tissue.

When activated, the insulin receptors cause vesicles containing glucose transporters that are inside the cell to fuse with the cell membrane, allowing glucose to be transported into the cell.

Glucagon does exactly the opposite, it raises the blood glucose levels by getting the liver to generate new molecules of glucose from other molecules and also break down glycogen into glucose so that it can all get dumped into the blood.

Diabetes mellitus is diagnosed when the blood glucose levels get too high, and this is seen among 10% of the world population.

There are two types of diabetes - Type 1 and Type 2, and the main difference between them is the underlying mechanism that causes the blood glucose levels to rise.

About 10% of people with diabetes have Type 1, and the remaining 90% of people with diabetes have Type 2.

Let’s start with Type 1 diabetes mellitus, sometimes just called type 1 diabetes. In this situation, the body doesn’t make enough insulin.

Sources

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
  6. "Hyperglycemic Crises in Adult Patients With Diabetes" Diabetes Care (2009)
  7. "MECHANISMS IN ENDOCRINOLOGY: Seizures and type 1 diabetes mellitus: current state of knowledge" European Journal of Endocrinology (2012)