A 45 yr. old woman has a fasting serum glucose concentration of 95 mg/dL (5.2 mmol/L) and a 2 hr. postprandial glucose concentration of 105 mg/dL (5.8 mmol/L). The statement which best describes this patient's fasting serum glucose concentration is:

• A. normal; reflecting glycogen breakdown by the liver
• B. normal; reflecting glycogen breakdown by skeletal muscle
• C. abnormal; indication diabetes mellitus
• D. abnormal; indicating hypoglycemia

Answer: (A)

The main idea is that fasting blood glucose is mainly controlled by the liver’s production of glucose through glycogenolysis. A fasting glucose of 95 mg/dL sits in the normal range, so it reflects normal hepatic glucose output during fasting rather than an abnormal state. The liver releases glucose by breaking down stored glycogen to keep blood sugar steady between meals.

Skeletal muscle, on the other hand, can break down its glycogen for its own energy needs, but it cannot raise blood glucose levels because muscle lacks the enzyme needed to release free glucose into the bloodstream. That’s why glucose produced from muscle glycogen doesn’t contribute to fasting blood glucose.

The other statements describe states that aren’t indicated here. Diabetes would typically show a higher fasting glucose (and/or high 2-hour values), while hypoglycemia would involve a much lower glucose level. The 2-hour postprandial value of 105 mg/dL is also normal, reinforcing overall normal glucose handling in this case.