Question from Midland, Texas, USA:

My 13-year-old daughter has recently seen an endocrinologist for lack of growth and a passing out episode. She was very healthy prior to January 2006 then had a mononucleosis-like virus and one infection after another. She has grown only about an inch in a year and a half and is of normal weight. She put on about 10 pounds between February and August and now has lost all of it following two episodes of pneumonia in the last six weeks. She has had two sets of laboratory work during the last two months. In October, she had an oral glucose tolerance test (OGTT). Her fasting glucose was 80 mg/dl [4.4 mmol/l] and her insulin level was 1.9 uU/mL; her two hour glucose was 105 mg/dl [5.8 mmol/L] with an insulin level of 17; her fasting C-Peptide was 1.1 ng/mL, while her two hour level was 6.2. A month later, she had fasting tests done. Her blood glucose was 83 mg/dl [4.6 mmol/L]; her insulin level was less than 2 uU/mL; her C-Peptide was 0.9 ng/mL; her T-4 (free) 1.0 ng/dL; her TSH was 3.65 mIU/L and her IGF-I was 169 ng/mL (reference range 199 to 658).

We were given a glucose meter to check her in the morning and evening for hypoglycemia with the only abnormal results being some spiking numbers, over 200 mg/dl [11.1 mmol/L], at bedtime. Fasting levels have been within the range with a few of the lowest ones being 69 mg/dl [3.8 mmol/L] and 72 mg/dl [4.0 mmol/L] and the highest being 110 mg/dl [6.1 mmol/L].. Are these insulin and C-Peptide levels normal? I know they have upper limits, but what about lower ones? We are scheduled to meet with the doctor again next week, but from talking to the nurse, it doesn’t seem that they think anything is out of the ordinary.