A 34-year-old obese man presents to your office complaining of fatigue, daytime sleepiness and occasional headaches. When you inquire about his sleeping habits, he reports that he sleeps in a separate room from his wife because she finds his snoring annoying. On physical examination, his blood pressure is 160/90 mmHg and his heart rate is 80/min. His abdomen is soft and non-tender, his liver span is 9 cm, and his spleen is not palpable. Laboratory findings are: Decreased oxygen delivery to which of the following organs is responsible for his increased hematocrit?

Question

A 34-year-old obese man presents to your office complaining of fatigue, daytime sleepiness and occasional headaches.  When you inquire about his sleeping habits, he reports that he sleeps in a separate room from his wife because she finds his snoring annoying.  On physical examination, his blood pressure is 160/90 mmHg and his heart rate is 80/min.  His abdomen is soft and non-tender, his liver span is 9 cm, and his spleen is not palpable.  Laboratory findings are:  Decreased oxygen delivery to which of the following organs is responsible for his increased hematocrit?

Quizplus · Accepted Answer

This patient most likely has obstructive sleep apnea (OSA), a disease characterized by recurrent episodes of asphyxia during sleep, often up to 500 times per night. In patients with OSA, peritubular cells in the renal cortex sense hypoxia and respond by releasing erythropoietin into the bloodstream. (Deficient erythropoietin production is the reason why many patients with chronic kidney disease develop anemia.) Erythropoietin stimulates erythrocyte production by binding to erythropoietin receptors on erythrocyte precursors in the bone marrow. This response is responsible for the secondary polycythemia that occurs in patients with chronic hypoxia secondary to OSA, COPD, right-to-left shunts and high altitude. (Choice A) Brain doesn't produce erythropoietin. (Choice B) The liver is the major site of erythropoietin production in the fetus. (Choice C) The spleen is the major site of destruction of aged or defective erythrocytes. The spleen and liver are potential sites of extramedullary hematopoiesis. (Choice D) Erythropoietin released by the kidneys circulates to the bone marrow where it stimulates erythroid progenitor cells to synthesize more erythrocytes. (Choice E) Lung stretch receptors sense distention of the lungs. Stimulation of these receptors decreases the respiratory rate. Educational Objective: Renal cortical cells sense hypoxia and respond by synthesizing and releasing erythropoietin. Erythropoietin stimulates the production of erythrocytes in the bone marrow.

A 34-Year-Old Obese Man Presents to Your Office Complaining of Fatigue