Review Question - QID 213221

A 46-year-old man presents to the clinic complaining of fatigue and difficulty breathing for the past month. He reports that it is particularly worse when he exercises as he becomes out of breath at 1 mile when he used to routinely run 3 miles. He is frustrated as he was recently diagnosed with diabetes despite a good diet and regular exercise. He denies any weight changes, chest pain, or gastrointestinal symptoms. When asked about other concerns, his wife complains that he is getting darker despite regular sunscreen application. A physical examination demonstrates a tanned man with an extra heart sound just before S1, mild bilateral pitting edema, and mild bibasilar rales bilaterally. An echocardiogram is ordered and shows a left ventricular ejection fraction (LVEF) of 65% with reduced filling. What is the most likely explanation for this patient’s condition?