The arginine stimulation test: timing of peak is not a helpful parameter in the diagnosis of growth hormone deficiency.

BACKGROUND A typical peak timing in the glucagon stimulation test has been reported as an indication of growth hormone (GH) deficiency. Other stimulation tests have not been evaluated. OBJECTIVE To evaluate the clinical usefulness of peak timing in the arginine stimulation test (AST) for growth hormone deficiency. METHODS Retrospective review of 199 ASTs from one center. Outcomes included correlation of peak times with (a) frequency of deficient peak; (b) growth velocity standard deviation scores (GVSDSs); (c) other evidence of pituitary pathology; (d) results of confirmatory clonidine test; and (e) response to GH treatment. RESULTS The peak in 83/109 (76.14%) sufficient tests occurred at typical times vs. 45/72 (62.5%) deficient tests (p<0.05). GVSDS on GH treatment was greater among patients with typical timing in the AST compared with atypical timing (2.67 ± 0.59 vs. 0.46 ± 1.17, p=0.021). No other variable correlated significantly with AST timing. CONCLUSIONS Timing of peak in the AST is not a clinically useful parameter.