1027 - Low Insulin-like Growth Factor-1 After Traumatic Brain Injury: Interpretation and Implications

This review provides a pragmatic clinical framework for interpreting low insulin-like growth factor-1 (IGF-1) levels (z-score < 0) in symptomatic patients who have suffered a traumatic brain injury (TBI). The primary aim is to guide clinicians in determining when to screen, pursue confirmatory testing, and consider differential diagnoses to optimize post-injury management. This is particularly important given the high prevalence of neuroendocrine dysfunction following TBI and its potential contribution to persistent symptoms impacting quality of life, functional outcomes, and rehabilitation progress.

Design:

A literature review was conducted, incorporating the 2019 Endocrine Society guidelines on growth hormone deficiency (GHD) evaluation, peer-reviewed studies examining neuroendocrine dysfunction after TBI, and established differential diagnoses associated with low levels of IGF-1. The review emphasized the importance of integrating neuroendocrine evaluation within a broader clinical context, considering non-endocrine factors and medical comorbidities that may affect IGF-1 levels. 

Results:

While GHD is a frequent cause of persistently low IGF-1 (z-score < 0) in TBI patients, alternative conditions must be systematically considered. These include malnutrition, chronic liver or kidney disease, poorly controlled diabetes mellitus, hypothyroidism, and rare genetic conditions such as Laron syndrome. The use of age- and sex-adjusted IGF-1 z-scores improves diagnostic precision and reduces the risk of misclassification. Screening is recommended for patients with persistent symptoms in the chronic phase of TBI, to be followed by confirmatory testing in those with low IGF-1 levels (z-score < 0). When indicated, dynamic GH stimulation testing remains the diagnostic gold standard for confirming GHD.

Conclusions:

Clinicians should adopt a structured, evidence-based approach to interpretation of IGF-1 levels after TBI, integrating laboratory results with clinical symptoms and additional confirmatory testing to ensure accurate diagnosis and employ targeted therapies. Future research should refine screening strategies for neuroendocrine dysfunction after TBI and explore therapeutic interventions to optimize recovery in TBI patients.