A comparison of l-dopa and clonidine growth hormone stimulation tests in children with short stature

Aim: The purpose of this study was to compare the results of L-dopa and clonidine GH stimulation tests applied in children with short stature and to identify which of these tests should be primarily selected. Materials and Methods: The records of 68 patients aged between 2.5 and 16.6 years presenting to the pediatric endocrinology clinic with short stature and undergoing GH stimulation tests between September 2016 and February 2021 were evaluated retrospectively. Cases with GH levels <10 ng/dl following the first GH stimulation test then underwent the other GH stimulation test. Thirty-four (50%) of the cases in the study consisted of individuals beginning with the clonidine test, while the other 34 (50%) started with the L-dopa test. Results: Thirty-five patients (51.5%) were girls and 33 (48.5%) were boys. Twenty-seven (79.4%) of the individuals in whom L-dopa was employed as the first test had insufficient GH responses, while a sufficient GH response could not be achieved in 18 cases (66.7%) with the clonidine test. Insufficient growth hormone responses were observed in 17 (50%) of the patients undergoing the clonidine test as the first test, and sufficient growth hormone response was also not achieved at the L-dopa test performed as the second test in 15 (88.2%) of these cases (p< 0.001). A cut-off point of 8.9 ng/dl was determined for 50% sensitivity and 100% specificity for the L-dopa test, and a cut-off point of 9.76 for 88% sensitivity and 94% specificity for the clonidine test. Conclusion: GH stimulation tests performed to investigate GHD are laborious and time-consuming. The first stimulation test to be applied to differentiate GHD from ISS must therefore be well selected. The clonidine stimulation test, with higher sensitivity than but similar specificity to the L-dopa test, can be employed as the first test.