Pituitary Dysfunction Following TBI: Update on the Importance of Stimulation Testing
In our May, 2014 post, we reported on research showing that traumatic brain injury, including mild traumatic brain injury (mTBI), can damage and cause dysfunction in the pituitary gland resulting in deficiencies in key hormones released by the pituitary gland, such as Growth Hormone (GH). As we explained in that post, the anatomy of the pituitary gland makes it particularly susceptible to the sheering injuries seen in TBI. The pituitary gland, which is housed in a bony structure at the base of the skull, controls the function of most other endocrine glands and is therefore sometimes called the “master gland.”
Pituitary dysfunction following TBI often impacts the production of growth hormone, which regulates metabolism and body composition as well as growth. These hormone deficiencies can produce many of the persistent symptoms seen following a TBI, such as fatigue, poor memory, depression, anxiety, emotional lability, exercise intolerance, lack of concentration and attention difficulties. Left untreated they can and lead to serious physical issues, including cardiac issues. osteoporosis, neuroanatomic and neurophysiologic dysfunction. We also noted findings showing that pituitary dysfunction can worsen over the five year period following an injury – in other words, that this is an issue that deserves to be monitored on an ongoing basis.
A study published in 2015 showed that the incidence of pituitary dysfunction in mTBI cases is highest in so-called “complicated mTBI” cases, with findings of skull fracture (especially skull base fractures, where the pituitary gland is housed) and/or intracranial abnormalities on imaging. Because of the high incidence of pituitary dysfunction in those cases, ongoing assessment was recommended, even where clinical manifestations are not clear.
In a more recent post, in 2016, we reported on a study of growth hormone deficiency following TBI published in the Journal of Neurotrauma. That study was important for three reasons:
- The first was the finding that the standard blood test commonly used to determine growth hormone deficiency, the IGF-1 test, is not an accurate predictor of growth hormone deficiency; a more costly and time consuming test, the “glucagon stimulation test,” proved to be a far more accurate assessment and was therefore recommended by the authors.
- The second reason the study was important is that it highlighted the serious physical, emotional and cognitive disabilities that can develop when growth hormone deficiency is not properly monitored and treated – as the authors explain, it can lead to “morbidity and poor recovery.”
- The third reason the study was important is that it added to the body of research showing the “high prevalence of growth hormone deficiency in patients with TBI and the necessity to monitor clinical symptoms and perform provocative testing [stimulation testing] to definitively diagnose this condition.”
The most recent study adding to this body of information was recently published (in April, 2018) in the peer-reviewed journal BMC Endocrine Disorders. Noting that stimulation testing is “resource intensive and can be associated with adverse symptoms or risks,” the authors took another look at whether the more simple IGF-1 blood test would suffice in most cases to assess growth hormone deficiency in TBI patients. The conclusion to the study is strongly worded. “Our results demonstrate,” the author’s state, “that baseline serum IGF-1 level had no predictive value [emphasis added] in predicting GH deficiency, emphasizing the need for dynamic testing in this population.” The authors further highlight that although growth hormone deficiency (the most common hormone deficiency follow TBI) may be more common in TBI cases involving skull base fractures or intracranial abnormalities on imaging, “even individuals who sustain a single concussion from non-contact sports appear to be susceptible to developing some degree of pituitary dysfunction.”
Because of the unique features of pituitary dysfunction following TBI and the testing necessary to detect this dysfunction, it is critical that patients be followed by endocrinologists (and other providers) with specialized knowledge in this area. The consequences of not treating this dysfunction are far too serious to overlook it.