Spontaneous hypoglycemia in patients with cystic fibrosis.
OBJECTIVE
Diabetes frequently complicates cystic fibrosis (CF) without fasting hyperglycemia or despite spontaneous hypoglycemia (anecdotally ascribed to malnutrition), whose prevalence, clinical meaning, and relationship with glucose tolerance and clinical/nutritional status were not previously investigated. The relationship of CF genotype with insulin secretion control is also unclear.


METHODS
A total of 129 CF patients without stable diabetes received 188 oral glucose tolerance tests. Distribution of fasting plasma glucose (FPG), glucose, insulin and C-peptide responses, clinical/nutritional variables, and their relationships were analyzed.


RESULTS
FPG < 60 mg/dl (3.3 mmo/l) was detected in 14% of studies and reactive hypoglycemia (PG < 50 mg/dl (2.8 mmo/l)) in 15%. OGTT-based diabetes frequency was similar in the lowest quartile (Q1) and Q2-3 for FPG (10 and 8%), with higher glucose increment and area under the curve in Q1. Insulin and C-peptide levels were similar among FPG quartiles. Class I cystic fibrosis transmembrane conductance regulator mutation carriers had higher insulin concentrations than class II, especially in Q1 for FPG. Age, sex, nutritional, and anthropometric parameters including fat and lean body mass were unrelated to FPG. Lower FPG was associated with more frequent hospitalization rates (P = 0.002) and lower Shwachman scores (P = 0.041). Steroids weaning was accurately evaluated but then excluded as a possible cause of hypoglycemia.


CONCLUSIONS
Fasting asymptomatic hypoglycemia is frequent and possibly related to inappropriate insulin secretion control in class I mutation carriers. Low FPG does not exclude impaired glucose tolerance (IGT) and diabetes in CF and reflects worse clinical status.
Battezzati
A
A
Department of Pediatrics, CF Center, Fondazione IRCCS Ospedale Maggiore Policlinico, Mangiagalli e Regina Elena, Italy. alberto.attezzati@unimi.it
Battezzati
P M
PM
Costantini
D
D
Seia
M
M
Zazzeron
L
L
Russo
M C
MC
Daccò
V
V
Bertoli
S
S
Crosignani
A
A
Colombo
C
C
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D015519:Bone Density; D002648:Child; D003550:Cystic Fibrosis / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics; D005215:Fasting; D005260:Female; D005838:Genotype; D005951:Glucose Tolerance Test; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000503:physiopathology; D007328:Insulin / Q000097:blood; D008297:Male; D009154:Mutation; D009752:Nutritional Status
D001786:Blood Glucose; D007328:Insulin; D019005:Cystic Fibrosis Transmembrane Conductance Regulator