One of the advancements for monitoring glycemic status is the development of continuous glucose monitoring system (CGMS) which gives 24 hour trend of blood sugar levels. The CGMS unit consists of a glucose sensor, inserted into the subcutaneous tissue which senses the interstitial fluid glucose levels electrochemically every 10 seconds and records an average value every 5 minutes, thus giving 288 values per day. The sensor can be left in situ for upto 72 hours. Compared to CGMS, finger-stick blood glucose values are indicative of point of time values only rather than the real time measures. Studies have demonstrated that patients with continuous sensors experience less glycemic variability and a better glycemic profile.

There are no studies in the literature where CGMS has been used for recurrent hypoglycemia. Its use in patients with congenital hyperinsulinism has also not been much reported. In this report, we present our experience with CGMS in an infant with congenital hyperinsulinism.

Growth hormone, cortisol, ACTH, free fatty acids, beta-hydroxy butyrate, calcium and C-reactive protein were within normal limits. At the time of hypoglycemic episode, serum insulin and c-peptide levels were 200 pmol/L and 7 ng/mL, respectively which led to a suspicion of congenital hyperinsulinism. Genetic sequencing confirmed the diagnosis of congenital hyperinsulinism. 18 fluro-L-Dopa PET scan done revealed diffuse variety of congenital hyperinsulinism.

Internal jugular central venous line was inserted to give higher percentages of dextrose (between 17-25%). Due to parental wishes to decrease the frequency of finger prick glucose monitoring, CGMS (Medtronic) was initiated as an off-label use for monitoring her glucose levels. CGMS helped in better titration of the dextrose concentration and the drugs being given to maintain her blood sugar levels. 24 hour trends were available which helped in better dosing time of diazoxide and octreotide so as to minimize the number of hypoglycaemic episodes.

During the intervening period while awaiting surgery, the infant was continued on CGMS and medical management. The frequent and severity of hypoglycemic events was reduced and hypoglycemic seizures were prevented. The infant was referred for near total pancreatectomy in view of the diffuse congenital hyperinsulinism.

Continuous glucose monitoring provides information about the direction, magnitude, duration, frequency, and causes of fluctuations in blood glucose levels. Compared with conventional intensified glucose monitoring, defined as three to four blood glucose measurements per day, continuous monitoring provides much greater insight into glucose levels throughout the day. Continuous glu-cose readings that supply trend information can help identify and prevent unwanted periods of hypo- and hyperglycemia.

In cases like ours, where frequent finger prick measurements are the only means of identifying hypoglycemias, CGMS can be an option to identify hypoglycemic episodes, especially in younger population in whom the symptoms of hypoglycaemia are difficult to recognise and can be potentially life threatening. Our experience with CGMS in our case of congenital hyperinsulinism has shown that it helps in early recognition of hypoglycemic attacks leading to prompt intervention so as to prevent seizures. Further, the timing of hypoglycemic events in relation to feeding may help in modifying the timings of anti-hypoglycemic medications.

Conrad, et al. [1] evaluated the sensitivity and specificity of the CGMS for reference capillary blood glucose levels <60 mg/dL in five children and infants with hypoglycemic disorders. They reported a sensitivity of 65%, a specificity of 91%, and a false-positive rate of 43%.

Some shortcomings are its prohibitive cost and a possibility of increasing mismatch between the values of finger prick method and CGM values as the sensor becomes old. As observed in our case, the values displayed by CGMS system corelated well for the first 36 hours with that of the values obtained by glucometer but gradually the values start demonstrating discrepancies with prolonged usage. However, meta-analysis have demonstrated that using the sensor for upto seven days can give relatively accurate results [2].

Contributors: IPSK clinically worked up and managed the case. He shall act as the guarantor. MS and AK collected all the data and prepared the manuscript. RJ revised the manuscript for important intellectual content. The final manuscript was approved by all the authors.

Funding: None; Competing interests: None stated

1. Conrad SC, Mastrototaro JJ, Gitelman SE. The use of a continuous glucose monitoring system in hypoglycemic disorders. J Pediatr Endocrinol Metab. 2004;17:281–8,