Endocrine Abstracts

Introduction: Traumatic brain injury (TBI) is the leading cause of death and disability in young adults. It is important to recognise pituitary dysfunction following TBI as it can cause significant morbidity.

Methods: 179 TBI patients (137 males) age 41.0±15.7 years (17.6–88.1 years) attended Charing Cross Hospital clinic (July 2009–August 2011). Median time since TBI was 0.27years (0.05–46.5 years, 26% >1 years). 34% had an intracranial bleed and 9% needed craniotomy. 20% had an absolute contraindication for insulin tolerance testing (ITT) and 42% a relative contraindication. Glucagon stress test (GST) was performed in 135 patients to assess GH and ACTH deficiency. A cortisol <350 nmol/L or GH <5 μg/l was considered abnormal. To confirm deficiency, patients who failed GST had a GHRH-Arginine test (GHRH-A) to assess GH response; a Metyrapone suppression test (MST) to assess ACTH deficiency; or a water deprivation test (WDT ) to assess for diabetes insipidus.

Results: No patients had TSH deficiency (0/174) or diabetes insipidus (11/174 had normal WDT), one patient had syndrome of inappropriate ADH. Two patients had asymptomatic hyperprolactinaemia (2/169) and three had gonadotrophin deficiency (3/170). 30/135 had a GST peak cortisol <350 nmol/l, but only 1/19 had confirmation of ACTH deficiency by failing a MST. None of the 14 patients with GST peak cortisol >350 nmol/l failed a MST. 35/135 had a GST peak GH <3 μg/l (25.9%) and 55/135 peak GH<5 μg/l (40.7%), but only 3/12 failed GHRH-A. Initiation of GH replacement in appropriate patients resulted in symptomatic improvement.

Conclusions: GST has a high false positive rate in diagnosing both GH and ACTH deficiency, likely due to the low pre-test probability of true pituitary dysfunction in this group. Thus, a second confirmatory test should be performed. In our cohort, clinically significant pituitary dysfunction was confirmed in 10/174 patients (5.7%). It is important to identify these patients, as treating the hormonal dysfunction is therapeutically beneficial.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.