This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Causes of fasting hypoglycemia are following except- 
Select and explain. 
A. Excess glucagon, B. Glucose 6 phosphatase deficiency, C. Uremia, D. Glycogen synthatase deficiency
A: Excess glucagon
Answer: A: Excess glucagon 
Explanation: Fasting hypoglycemia In otherwise healthy people, prolonged fasting (even up to several days) and prolonged strenuous exercise (even after a period of fasting) are unlikely to cause hypoglycemia. However, there are several diseases or conditions in which the body fails to maintain adequate levels of glucose in the blood after a period without food (fasting hypoglycemia). In people who drink heavily without eating, alcohol can block the formation of glucose in the liver. In people with advanced liver disease, such as viral hepatitis, or cancer, the liver may not be able to store and produce sufficient glucose. Infants and children who have an abnormality of the enzyme systems that control glucose use (such as a glycogen storage disease) also may have fasting hypoglycemia. A rare cause of fasting hypoglycemia is an insulinoma , which is an insulin-producing tumor in the pancreas. Disorders that lower hormone production by the pituitary and adrenal glands (most notably Addisons disease) can cause hypoglycemia. Other diseases, such as CKD , hea disease, cancer, and sepsis, may also cause hypoglycemia, especially in critically ill people. Causes of Hypoglycemia Ref - pubmed.com