ITT is the test of reference for the diagnosis of adult GH deficiency (GHD), but also GHRH in combination with arginine (ARG) or GH secretagogues (GHS) are considered equally reliable tests. Testing with GHS alone is, anyway, a potent stimulus exploring the integrity of hypothalamic pathways controlling somatotropic function.
We therefore aimed to clarify the diagnostic reliability of testing with ghrelin, the natural GHS.
We studied the GH response (every 15 min from −15 to +120 min) to acylated ghrelin (1 μg/kg i.v. at 0 min) in 78 patients with history of pituitary disease (49 M, 29 F; age [mean±SD]: 52.1±18.7 years; BMI: 26.7±5.3 kg/m2). As gold standard for the diagnosis of GHD we assumed the lack of GH response to GHRH+ARG and/or ITT. We identified the best GH cut-off to ghrelin test, defined as the one with the best sensitivity (SE) and specificity (SP), using the ROC analysis.
The best GH cut-off to ghrelin test was 7.3 μg/l in lean subjects with a SE and SP value of 88.2 and 90.9%, 2.9 μg/l in overweight subjects with a SE and SP value of 92.6 and 100%, and 0.6 μg/l in obese subjects with a SE and SP value of 50 and 100%. The diagnostic accuracy was 89.3, 94.1 and 62.5%, respectively.
In conclusion, these findings indicate that testing with acylated ghrelin would represent a reliable diagnostic tool for the diagnosis of adult GHD, at least in lean and overweight subjects provided that appropriate cut-off limits are assumed. Obesity strongly reduces the GH response to ghrelin, its weight-related cut-off limit, and its diagnostic reliability.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
05 - 09 May 2012
European Society of Endocrinology