Pituitary deficiency 3 and 12 months after traumatic brain injury or subarachnoid hemorrhage – A prospective longitudinal study on pituitary function using different methods of dynamic neuroendocrine evaluation

Objective: Recent cross-sectional and prospective longitudinal studies report a high rate of pituitary deficiency after traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). However, the reported prevalences are very heterogenous and seem to be dependent on the chosen endocrine tests and the defined normal treshholds. This prospective-longitudinal study was conducted to assess hypopituitarism 3 and 12 months after TBI or SAH using induced hypoglycaemia (ITT) and therefore the gold-standard in the evaluation of hypothalamo-pituitary dysfunction, whenever possible. Methods: We have prospectively evaluated the anterior pituitary function in 163, 58 and 40 consecutive patients in the acute, sub-acute (3 months) and chronic (12 months) phase after TBI or SAH. ITT was performed in 43 after 3 months, and 29 patients after 12 months. Whereas, a GHRH-arginine-CRH test has to be used in 15 patients after 3 months, and 11 patients after 12 months. GH deficiency was defined as GH <3.0ng/ml (ITT) or BMI adapted (GHRH-arginine) as GH <11.5ng/ml (lean), <8.0ng/ml (overweight) or 4.2ng/ml (obese). Corticotropic defiency was defined as stimulated peak cortisol <18.1µg/dl. Male hypopituitarism was defined as testosterone levels <2.31ng/ml. Results: The overall rate of GH-deficiency after 3 and 12 months was 15.8% and 17.5%, respectively. However, GH-deficiency according to the ITT was 0% at both time points. Male hypogonadism was found in 6.7% (3 months) and 0% (12 months). The prevalence of adrenocorticotropic insufficiency was 10.5% (3 months) and 5% (12 months). Conclusion: Our data suggest a high correlation between the reported prevalence of somatotropic and corticotropic insufficiency in patients after TBI or SAH and the chosen dynamic endocrine test. The discrepancy between the rate of GH deficiency using the ITT in comparison to the GHRH-arginine test suggests that the latter may not be adequate to evaluate the hypothalamo-pituitary function in patients after TBI or SAH.