Responses to GHRH plus arginine test are more concordant with IGF-I circulating levels than responses to arginine and clonidine provocative tests

"Rina Balducci" Center of Pediatric Endocrinology, Tor Vergata University, Rome, Italy. .
Journal of endocrinological investigation (Impact Factor: 1.45). 10/2011; 35(8):742-7. DOI: 10.3275/8008
Source: PubMed


Although pharmacological GH stimulation tests are still considered the gold standard for GH deficiency (GHD) diagnosis, they are burdened by poor specificity. The majority of children diagnosed as having GHD show normal GH responses when re-tested at the end of growth, thus questioning the initial diagnosis. We evaluated the concordance between IGF-I levels and GH responses to provocative tests.
We analyzed 105 GHRH plus arginine tests, 79 arginine tests, and 124 clonidine tests performed in 192 short children. IGF-I levels ≤-2SD score (SDS) were considered suggestive for high likelihood of GHD. The percentage of positive and negative results for each test was determined and compared with IGF-I levels, clinical follow-up and response to therapy.
In children with IGF-I>-2SDS the arginine test showed a concordance rate of 6.9%, the clonidine test of 28.6%, and GHRH plus arginine test of 70%. In children with IGF-I≤-2SDS the concordance was 96.1%, 85.7%, and 46.4%, respectively. The overall concordance was 66.7% for GHRH plus arginine, 42.7% for clonidine, and 27.8% for arginine tests.
Our results suggest that GHRH plus arginine test provides the best concordance with the assessment of IGF-I levels thus suggesting that the combination of the two procedures may significantly reduce the need of a second provocative test.

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    • "An alternative test is the combined stimulation with Growth Hormone Releasing Hormone and arginine (GHRH + Arg). It shows excellent sensitivity and specificity both in childhood and in adulthood, assuming appropriate cut-off limits (Corneli et al., 2007; Giacomozzi et al., 2012) but its reliability is uncertain in patients with hypothalamic impairment. Therefore, a normal GH response to GHRH + Arg test in a patient with ascertained hypothalamic alterations should induce suspicion for a false negative result. "
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