Does clonidine stimulate copeptin in children?

Objectives: Copeptin is secreted in isomolar amounts along with AVP. Its stability makes it a perfect biomarker of AVP deficiency. In children, dynamic GH tests were shown to stimulate copeptin. Here, we retrospectively studied the effect of clonidine on copeptin release.

Methods: This is a monocentric retrospective analysis of donated residual serum samples from 42 children with suspected growth hormone deficiency (GHD) who underwent clonidine stimulation between 2020 and 2023. Copeptin was measured in baseline, 30-, 60-, 90- and 120-min samples by BRAHMS Copeptin proAVP Kryptor immunofluorescence assay.

Results: There were 20 patients with GHD and 22 without; no patient had polyuria-polydipsia syndrome. Median age was 6.7 years (quartiles; 5.6-7.8), and the median height was -2.92 SDS (-3.42 to -2.34). The median baseline level of copeptin was 5.6 pmol/L (3.4-9.6). Median copeptin mildly decreased to 4.5 pmol/L (3.0-10.0) after 30 min; this change was not significant (p=0.45). Thereafter, median values remained low at 4.6, 4.6, and 4.6 pmol/L (60, 90, and 120 min). There was no correlation between baseline copeptin levels and the diagnosis of GHD.

Conclusions: The clonidine stimulation test does not stimulate copeptin release and is not suitable for the assessment of AVP deficiency in children.