Abstract
BackgroundGrowth hormone deficiency (GHD) is a potential consequence of traumatic brain injury (TBI), including sport-related concussion (SRC). GH stimulation testing is required for definitive diagnosis; however, this is resource intensive and can be associated with adverse symptoms or risks. Measurement of serum IGF-1 is more practical and accessible, and pituitary tumour patients with hypopituitarism and low serum IGF-1 have been shown to have a high probability of GHD. We aimed to evaluate IGF-1 measurement for diagnosing GHD in our local TBI population.MethodsWe conducted a retrospective chart review of patients evaluated for GHD at the TBI clinic and referred for GH stimulation testing with insulin tolerance test (ITT) or glucagon stimulation test (GST) since December 2013. We obtained demographics, TBI severity, IGF-1, data pertaining to pituitary function, and GH stimulation results. IGF-1 values were used to calculate z-scores per age and gender specific reference ranges. Receiver operator curve analysis was performed to evaluate diagnostic threshold of IGF-1 z-score for determining GHD by GST or ITT.ResultsSixty four patient charts were reviewed. 48 patients had mild, six had moderate, eight had severe TBI, and two had non-traumatic brain injuries. 47 patients underwent ITT or GST. 27 were confirmed to have GHD (peak hGH < 5 μg/L). IGF-1 level was within the age and gender specific reference range for all patients with confirmed GHD following GH stimulation testing. Only one patient had a baseline IGF-1 level below the age and gender specific reference range; this patient had a normal response to GH stimulation testing. ROC analysis showed IGF-1 z-score AUC f, confirming lack of diagnostic utility.ConclusionBaseline IGF-1 is not a useful predictor of GHD in our local TBI population, and therefore has no value as a screening tool. TBI patients undergoing pituitary evaluation will require a dynamic test of GH reserve.
Highlights
Growth hormone deficiency (GHD) is a potential consequence of traumatic brain injury (TBI), including sport-related concussion (SRC)
GH stimulation testing is required for definitive diagnosis of GHD; the insulin tolerance test (ITT) is considered the reference standard and the glucagon stimulation test (GST) is an acceptable alternative, this testing is time consuming, resource intensive, and can be associated with adverse side effects [5]
Two patients (4%) patients had borderline results with a peak GH levels of 5.2 and 5.5 μg/L following GST and were classified as GHD at the discretion of the treating clinician, as therapy was offered to these patients due to symptomatology in keeping with growth hormone deficiency
Summary
Growth hormone deficiency (GHD) is a potential consequence of traumatic brain injury (TBI), including sport-related concussion (SRC). The IGF-1 method changed from a manual to an automated method during this study, and these findings have not been validated in a population that includes patients with mild, moderate, and severe traumatic brain injuries or sports-related concussion (SRC). The latter point is especially relevant considering patients with mild TBI have significant risk of neuroendocrine dysfunction [8]. Our primary objective was to evaluate the performance of IGF-1 as a screening tool for GHD in a patient population that includes mild (including SRC), moderate, and severe TBI
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