Which diagnostic tests are recommended for confirming growth hormone deficiency in adults?

Recommended diagnostic tests for confirming growth hormone deficiency (GHD) in adults primarily involve growth hormone stimulation tests, as basal GH levels are not reliable due to pulsatile secretion. The insulin tolerance test (ITT) is considered the gold standard for diagnosing adult GHD, as it evaluates the pituitary’s capacity to secrete GH in response to hypoglycaemia, which is a potent stimulus ¹.

Alternative stimulation tests include the glucagon stimulation test and the growth hormone-releasing hormone (GHRH) plus arginine test, which are used when ITT is contraindicated or not feasible, such as in patients with seizures or cardiovascular disease ¹. These tests provoke GH secretion through different mechanisms and have been validated for diagnostic accuracy (Gabellieri et al., 2010; Hazem et al., 2011).

It is important to interpret stimulation test results in the context of clinical features and IGF-1 levels, although IGF-1 alone is insufficient to confirm GHD due to variability and overlap with normal ranges (Feingold et al., 2000). Confirmatory testing is recommended when clinical suspicion is high, especially in patients with multiple pituitary hormone deficiencies or known hypothalamic-pituitary disease ¹.

Recent meta-analyses support the high diagnostic accuracy of ITT and glucagon stimulation tests, with GHRH plus arginine also showing good performance, but highlight the need for standardised protocols and cut-off values tailored to assay methods and patient characteristics (Hazem et al., 2011).