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C-peptide reliably predicts insulin secretion in children with GH deficiency
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In children with growth hormone deficiency, C-peptide measurements provide a better estimate of insulin secretion than insulin levels throughout the first 12 months of growth hormone therapy, according to recent study findings.
“Given the insulin antagonist action of GH, in addition to the direct stimulatory effect on beta cell, GH [therapy] can lead to glucose metabolism impairment through decreased insulin sensitivity and impaired pancreatic beta-cell function,” Alessandro Ciresi, of the biomedical department of internal and specialist medicine at the University of Palermo, Italy, and colleagues wrote. “Therefore, a reliable evaluation of the insulin secretion in GH-[deficient] children during GH [therapy] is very important.”
Ciresi and colleagues analyzed data from 48 prepubertal children with GH deficiency from 2012 to 2013 (32 boys; mean age, 10 years) and 56 healthy children with short stature who served as controls matched for age, sex, stature and pubertal status (39 boys; mean age, 10 years). All participants received GH therapy for 24 months, with dosage gradually increasing to 0.033 mg/kg daily during the study period. GH secretion, as well as fasting and glucagon-stimulated C-peptide levels were assessed at baseline and 12 and 24 months. Primary outcome was change in C-peptide during treatment and its association with auxologic and hormonal parameters.
Researchers found that children with GH deficiency had lower area under the curve (AUC) C-peptide vs. controls (436 ng/mL vs. 537 ng/mL; P = .006); there were no between-group differences for other insulin-secretion indexes. In multivariate analysis, fasting C-peptide (P = .016) and AUC C-peptide (P = .002) were independently associated with insulin-like growth factor I.
At 12 months, researchers observed an increase in homeostatic model assessment of beta-cell function vs. controls (28.8 vs. 9.7; P < .001), fasting C-peptide (1.7 ng/mL vs. 1.3 ng/mL; P = .002) and AUC C-peptide (521 ng/mL vs. 436 ng/mL; P < .001), without an observed change in the insulinogenic index and AUC insulin. In multivariate analysis, only fasting C-peptide (P = .001) and AUC C-peptide (P < .001) were independently correlated with IGF-I.
“We suggest the use of [glucagon stimulation test] not only as a diagnostic test for the GH assessment at baseline but also as a useful tool, instead of the [oral glucose tolerance test], for the evaluation of insulin secretion during GH [therapy] in children, at least during the first year, to simplify the test in clinical practice and to reduce costs and resources,” the researchers wrote. “Additional, larger case-control studies with longer follow-up will validate these results.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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