Exogenous insulin requirements do not differ between youth and adults with cystic fibrosis related diabetes

To examine whether insulin requirements and diabetes control differ between adolescents and adults with cystic fibrosis related diabetes (CFRD).

All CFRD patients on insulin therapy seen at the University of Minnesota outpatient clinic from 1 January 2011 to 1 June 2012 were identified. Hemoglobin A1c (HbA1c) levels obtained during this period were averaged for each patient, and the most recent outpatient insulin dose was obtained. In addition, retrospective chart review was performed in order to obtain longitudinal data on insulin requirements during the transition from adolescence to adulthood.

Eighteen youth aged 14-19 yr and 137 adults aged 20-67 yr were identified to be currently on insulin therapy. The average insulin dose was 0.38 ± 0.29 units/kg/d for adolescents and 0.46 ± 0.30 units/kg/d for adults (p = 0.20). In adults, insulin doses were significantly higher in transplant recipients: Tx = 0.58 ± 0.29, no Tx = 0.43 ± 0.30 (p = 0.005). Average HbA1c was 6.9 ± 2.1% in youth and 6.9 ± 1.5% in adults (p = 0.35). There were no changes in the insulin dosage when adolescents transitioned to adulthood with diabetes were not on higher doses of insulin compared to when they were adolescents with diabetes.

Modest insulin requirements suggest the persistence of endogenous insulin secretion in both youth and adults with CFRD. In adolescents, residual endogenous insulin secretion likely compensates for the insulin resistance during puberty, keeping insulin requirements low.