# Hypoglycemia and carbohydrate metabolism

### Problem

Mrs. Gierke brought her two-year-old son to her son’s pediatrician, Dr. Von, because she noticed that he appeared to be “clammy and fussy” a couple hours after feeding in recent months. “He’s vomited a couple times and I even took him to the ER yesterday because he was having a seizure,” she exclaimed, clearly frightened and worried about her son. After assuring Mrs. Gierke that she would find the answer, Dr. Von began a thorough physical exam of the young boy. On exam, Dr. Von palpated the boy’s abdomen and found that the boy’s liver was enlarged. She also checked the boy’s growth curve and noticed that he wasn’t growing as well as he should be – he was in the 5th percentile for height and weight. After taking a full history of the boy’s past medical history and symptoms, Dr. Von recommended Mrs. Gierke have her son undergo a carefully monitored fast at the hospital to detect if blood glucose levels are dropping too much after a meal. “Hypoglycemia, or very low blood sugars, may explain your son’s symptoms,” she explained. Mrs. Gierke agreed to the test. After eating a meal, the boy’s blood glucose levels were monitored for several hours after a meal. Normal blood glucose levels are 60-150 mg/dL. The results are shown in Figure 1.
Figure 1. Glucose Tolerance Test Results. A meal was given at Time = 0 and blood glucose levels were monitored. The boy's test results are shown alongside a normal (expected) curve.
Upon seeing the results, Dr. Von suspected that the boy was suffering from a metabolic disorder that did not allow him to appropriately maintain blood glucose levels after a meal. She ordered that a specimen of the boy’s liver be analyzed for possible enzyme deficiencies in the metabolism of glucose. Unfortunately, when the lab results came back, Dr. Von’s computer tablet suddenly froze and only a portion of the test results were visible, shown in Figure 2.
Name of EnzymeIs the enzyme involved in glycolysis?Is the enzyme involved in gluconeogenesis?Is the enzyme deficient or normal?
YesNo
YesYes
NoYes
Figure 2. The boy's (incomplete) enzyme assays from analysis of a piece of his liver.
Dr. Von diagnoses the patient with a deficiency in an enzyme that alters the phosphorylation state of a metabolite in gluconeogenesis. Based on your understanding of carbohydrate metabolism and the clinical picture outlined in the passage, which of the following is most likely TRUE?
Please choose from one of the following options.