9. Neuroendocrine Function and Disorders Following Acquired Brain Injury
|ABI||Acquired Brain Injury|
|Glasgow Coma Scale
|GHD||Growth Hormone Deficiency|
|GHRH||Growth Hormone-Releasing Hormone|
|GST||Glucagon Stimulation Test|
|IGF||Insulin-Like Growth Factor I|
|ITT||Insulin Tolerance Test|
Magnetic Resonance Imaging
|Randomized Controlled Trial
Syndrome of Inappropriate Antidiuretic Hormone
|TBI||Traumatic Brain Injury|
Syndrome of inappropriate antidiuretic hormone secretion may be effectively controlled with thyrotropin-releasing hormone (TRH) stimulation.
Growth hormone deficiency may be effectively treated with hormone replacement therapy and insulin growth like factor-1 therapy.
Progesterone may be effective in treating long-term outcomes in gonadotropic deficiency.
Hypopituitarism is a common and treatable condition resulting from an ABI. Post-traumatic neuroendocrine disorders involving the pituitary gland can be divided into posterior or anterior pituitary dysfunction depending on which anatomical area is involved. This module explores the variety of disorders which can arise from neuroendocrine dysfunction and discusses relevant interventions. However, with the variety of disorders which can develop as a result of neuroendocrine dysfunction, specific ABI evidence is not always available, in these instances the most relevant research is discussed and provides an opportunity for further research.
9.1.1 Anatomy of the Pituitary Gland
9.1.2 History and Epidemiology
9.1.3 Signs and Symptoms
In the acute phase, very early hormonal alterations may reflect adaptive responses to injury and critical illness, and are not necessarily associated with long-term PTHP. Various studies have shown that the majority of patients with low-grade or isolated deficiencies recover during the first 6 months post injury and tend to have a much better prognosis than those who do not recover (Aimaretti, Ambrosio, Di Somma, et al., 2004; Bondanelli et al., 2004; Ghigo et al., 2005). In one study, 5.5% of patients who showed no signs of PTHP deficiencies at 3 months did so at 12 months. The same study showed that 13.3% of patients who demonstrated isolated deficiencies at 3 months developed multiple deficiencies at 12 months (Ghigo et al., 2005). Growth hormone deficiency has been shown to be the most common deficit (Bondanelli et al., 2004; Ghigo et al., 2005).
Due to the nature of its features and the delay of its presentation, hypopituitarism may be missed following any type of acquired brain injury (ABI) (Klionsky et al.) (H. J. Schneider, Aimaretti, et al., 2007); thus, the diagnosis of hypopituitarism following an ABI remains a challenge. Some of the key indicators, such as low serum-like growth factor, may already be low in older patients due to normal aging. Studies examining this issue indicate that TBI severity, as measured by the GCS or EEGs, is not an accurate indicator of the likelihood of developing hypopituitarism. However, one study did show a non-significant trend to show an association with TBI severity (Sirois, 2009).
9.1.4 Association with Severity of ABI
Benvenga et al. (2000) have noted that PTHP is primarily a disorder seen much more often in male survivors between the ages of 11 and 39. This is likely related to the fact that young males tend to sustain head injuries most often. Currently there is no evidence that specific types of head injuries are more likely to lead to hypopituitarism (Ghigo et al., 2005). Due to the life threatening consequences associated with pituitary dysfunction, it represents a negative prognostic factor (Benvenga et al., 2000).
9.1.5 Diagnosis and Screening for Hypopituitarism
Given that hypopituitarism can evolve over time following injury, it is important to begin screening as soon as possible. In the acute stage, screening for adrenal insufficiency is particularly important due to its life threatening potential (Bernard, Outtrim, Menon, & Matta, 2006). During the acute stage of recovery, cortisol levels of less than 7.2 µg/dL may indicate adrenal insufficiency. Treatment should also be considered and initiated in cases where hyponatremia, hypotension, and hypoglycaemia are present, even if cortisol levels are between 7.2 and 18 µg/dL (H. J. Schneider, Aimaretti, et al., 2007). For those who have extended stays in the ICU and increased intracranial pressure, diffuse axonal injury, or basal skull fractures, assessing pituitary function should be considered. In the acute stage of recovery it is not necessary to assess growth, gonadal, or thyroid hormones as there is no evidence to suggest that supplementation of these hormones during this phase is beneficial (Ghigo et al., 2005; H. J. Schneider, Aimaretti, et al., 2007); however, during the post recovery stage, at 3 and 6 months, a clinical assessment for hypopituitarism should be completed (Powner & Boccalandro, 2008; Powner, Boccalandro, Alp, & Vollmer, 2006; H. J. Schneider, Aimaretti, et al., 2007). This is especially important if any of the following symptoms are noted: loss of secondary hair, impaired sexual function, weight changes, polydipsia, or amenorrhea.
Hormonal screening should include morning serum cortisol, fT3, fT4, TSH, FSH, LH, PRL, Insulin-like Growth Factor (IGF-I), testosterone in men, and estradiol in women. In patients with polyuria or suspected DI, sodium and plasma osmolality and urine density should also be evaluated. Low IGF-I levels strongly predict severe GH deficiency (in the absence of malnutrition). However, normal IGF-I levels may be found in patients with GH deficiency as well; therefore, provocative tests are necessary in patients with another identified pituitary hormone deficit. Provocative testing is recommended if IGF-I levels are below the 25th percentile of age-related normal limits (Ghigo et al., 2005).
Although neuroimaging (MRI or CT scans) can be successful in locating lesions within various sections of the brain, they do not reveal all pathology. Benvenga et al. (2000) found that 6% to 7% of those with PTHP showed no abnormalities on MRI. With regard to testing, blood tests remain the gold standard. Benvenga et al. (2000) suggested monitoring individuals for hypopituitarism if they are male and under the age of 40, have sustained their injury in a motor vehicle collision, and are within the first year post injury.
9.1.7 Provocative Testing
Approximately 20% of those with a TBI or subarachnoid hemorrhage (SAH) are at risk for severe growth hormone deficiency (Klionsky et al.); provocative testing has been recommended in order to rule it out. Due to the expense of this test, it is recommended that other hormonal tests are conducted first, such as the IGF-I, , and that provocative testing is used only to rule out other transitory hormone deficits (Sesmilo et al., 2007). It is not recommended to use Insulin Growth Factor (IGF) levels as an assessment of overall growth hormone as multiple studies have found no association between the two (Bondanelli et al., 2005; Popovic et al., 2005).
Pituitary Function Testing (Serum Cortisol, ACTH)
The diagnosis of adrenocortical insufficiency requires provocative tests in addition to measurement of early morning basal serum cortisol levels. The normal basal morning serum cortisol values are between 150 nmol/L and 800 nmol/L (5.3–28.6 lg/dL). Basal morning serum cortisol <100 nmol/L (<3.6 lg/dL) is indicative of secondary adrenocortical insufficiency; if this value is >500 nmol/L (>18 lg/dL) adrenocortical insufficiency can be excluded. When basal serum cortisol values are borderline, a provocative test is necessary (Auernhammer & Vlotides, 2007).
Short ACTH Stimulation Test
In healthy subjects, stimulated serum cortisol has been shown to be between 550 nmol/L and 1110 nmol/L (19.6–39.6 lg/dL). Adrenocortical insufficiency is confirmed with a serum cortisol <500 nmol/L (18 lg/dL). Standard ACTH tests should be conducted at least 4 weeks after pituitary surgery (Auernhammer & Vlotides, 2007).
Insulin-Induced Hypoglycemia Test
During an insulin-induced hypoglycemia test, the top serum cortisol levels in healthy people are between 555 nmol/L and 1,015 nmol/L (19.8–36.2 lg/dL) (Auernhammer & Vlotides, 2007). Adrenocortical insufficiency is diagnosed when there is a serum cortisol increase of <500 nmol/L. Although this test has been shown to be the gold standard, caution is recommended when using the test, especially for the cardiac and epileptic patient where this test has been found to be contraindicated.
Metyrapone has been shown to block the last step in the biochemical pathway between cholesterol and cortisol, leading to a reduction in serum cortisol, an increase of ACTH secretion and an increase of cortisol precursors such as 11b-deoxycortisol. The peak serum 11b-deoxycortisol levels in healthy people range between 195 nmol/L and 760 nmol/L. During the test, serum 11-deoxycortisol may increase to >200 nmol to exclude adrenal insufficiency. Another variant of the test is the ‘‘multiple dose metyrapone test’’, which requires other diagnostic cut-offs of serum 11b-deoxycortisol levels. In order to support this multistep testing, patients must be hospitalized. Metyrapone may cause gastrointestinal upset and may lead to adrenal insufficiency (Auernhammer & Vlotides, 2007). This test is considered only when other tests are inconclusive.
Corticotropin-Releasing Hormone (CRH) Test
Responses to this test vary widely between patients. Serum cortisol may increase to <350–420 nmol/L (<12.5–15 lg/dL) as evidence of secondary adrenocortical insufficiency, or it may increase to >515-615 nmol/L (18.5–22.0 lg/dL) excluding secondary adrenocortical insufficiency (Auernhammer & Vlotides, 2007).
9.2 Pathophysiology of Hypopituitarism Post ABI
9.2.1 Mechanism of Injury
Potential lesions associated with TBI are shown in Table 9.5. The types of injuries and respective rates are listed below in Table 9.6.
9.2.2 Isolated and Combined Hormone Deficiencies
9.3 Disorders of Neuroendocrine Function and Available Interventions
9.3.1 Timing of Interventions
Conditions that require immediate treatment are dysfunction of ACTH, ADH, and TSH. GHD has been shown to improve with time and may improve as other deficiencies improve. As well, GHD treatment in the acute phase is not recommended, as there appears to be no benefit (Sirois, 2009). When there is clear indication of anterior or posterior pituitary dysfunction, consulting an endocrinologist is strongly recommended (Estes & Urban, 2005).
9.3.2 Interventions for Posterior Pituitary Dysfunction
18.104.22.168 Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
When higher doses of sodium supplementation are found to be ineffective, hydrocortisone may be considered as treatment (Moro et al., 2007). These interventions may be administered alone or with loop diuretics (Arai, Fujimori, Sasamata, & Miyata, 2009). Conivaptan is a medication that has been approved to treat hypervolemic hyponatremia, although it has yet to be studied within the ABI population.
Findings from three studies suggest that while SIADH post injury is not overly common, it has a greater incidence among patients with severe injuries than those with moderate or mild injuries (Born, Hans, Smitz, Legros, & Kay, 1985; Doczi et al., 1982). The onset of SIADH may present as early as 2 to 3 days post injury (Born et al., 1985), but it may also persist beyond 12 months (Moreau, Yollin, Merlen, Daveluy, & Rousseaux, 2012). Depending on the diagnostic criteria, SIADH is recognized as “severe” if serum sodium is <125-130 mmol/L (Born et al., 1985; Doczi et al., 1982). Severe syndromes may be associated with poorer neurological function compared to moderate syndromes, and may require daily fluid restriction to resolve symptoms (Born et al., 1985). There is not a widely accepted target range for fluid restriction. However, Doczi et al. (1982) suggested limiting daily fluid intake to less than 600-800mL, whereas Born et al. (1985) suggest limiting intake to 250-500mL.
From three studies, the prevalence of hyponatremia post ABI ranged from 15% to 40% (Hannon et al., 2013; Moro et al., 2007; Zhang et al., 2010). Findings suggest that hyponatremia is more common in patients with severe, as opposed to mild or moderate, ABI (Zhang et al., 2010). Hyponatremia is undesirable during recovery as it is associated with longer administration days and worse outcomes at 1 month from treatment (i.e., limited ‘good’ recovery, higher number of patients with moderate disability) (Moro et al., 2007).
Recommendations for the management of hyponatremia resulting from SIADH include limiting daily fluid intake and TRH stimulation (Zhang et al., 2010). The former, in particular, directly decreases the level of circulating ADH in blood, and thus may represent an effective therapy for SIADH-induced hyponatremia. Its effectiveness, however, is limited against hyponatremia resulting from Cerebral Salt-Wasting Syndrome (Zhang et al., 2010) . Other ways to manage post-injury hyponatremia include IV or oral Na+ supplementation . Higher dosages of Na+ may be necessary if hyponatremia persists, and hydrocortisone should be considered if sodium supplementation is ineffective (Hannon et al., 2013; Moro et al., 2007). Moro et al (2007) reported that among patients with hyponatremia who did not respond to Na+ supplementation initially, hydrocortisone therapy was initiated, and their serum Na+ returned to normal range within 2 days of therapy. In conclusion, thyroid releasing hormone therapy, and sodium supplementation may be an effective treatment for managing hyponatremia.
22.214.171.124 Diabetes Insipidus (DI)
In general, post-ABI DI is an uncommon condition. In a large observational study by Hadjizacharia et al. (2008), 15% patients with either blunt or penetrating head injury were diagnosed with DI. In studies with smaller samples, the rates ranged from approximately 2.0% (Bondanelli et al., 2007; Born et al., 1985; Ghigo et al., 2005) to 14% (Bondanelli et al., 2004), while a single study finding DI among 51% of participants (Hannon et al., 2013). DI appears to have a relatively early onset, occurring within a week of injury (Kelly et al., 2000), or even within a few days (Hadjizacharia et al., 2008). While most studies suggest that post-injury DI is transient (Bondanelli et al., 2004; Hannon et al., 2013; Kelly et al., 2000; H. J. Schneider et al., 2006; M. Schneider et al., 2008), there is some evidence that DI may persist up to 3 months and even 12 months post injury (Ghigo et al., 2005). With regards to treatment, desmopressin has been shown to reduce urine output and liquid intake after head injury (Alaca, Yilmaz, & Gunduz, 2002; Born et al., 1985; Hannon et al., 2013).
Multiple risk factors for DI post ABI have been identified (Hadjizacharia et al., 2008). Multivariable analysis showed that patients with severe injury, brain edema, head Abbreviated Injury Score greater than or equal to 3, and/or intraventricular hemorrhage were at a greater risk of developing DI following ABI. There are suggestions that extensive fractures at the base of the skull may also be an important risk factor for DI (Born et al., 1985). Presence of DI may also predict deficiencies in other pituitary axes, such as hypogonadism (M. Schneider et al., 2008). Further, DI has been reported as significantly associated with higher mortality in individuals with TBI (Hannon et al., 2013), as well as a leading cause of death in those who sustain a severe TBI (Maggiore et al., 2009).
9.3.3 Anterior Pituitary Dysfunction and Available Interventions
Several studies have examined the prevalence of anterior pituitary deficiencies following ABI. The rate varies widely across studies, ranging from 15.4% to 76.4% (Bondanelli et al., 2007; Hannon et al., 2013; Klose et al., 2007; Kopczak et al., 2014; Moreau et al., 2012; Nemes et al., 2015; Prodam et al., 2013; Rosario et al., 2013; Ulfarsson et al., 2013). The onset of anterior pituitary deficiencies may occur within 24 hours of injury (Olivecrona, Dahlqvist, & Koskinen, 2013; F. Tanriverdi et al., 2007) and may persist up to 12 months post injury, and in some cases longer (Agha, Phillips, O’Kelly, Tormey, & Thompson, 2005; Agha et al., 2004; Bondanelli et al., 2007; Bondanelli et al., 2004; Ghigo et al., 2005; Kelly et al., 2000; Lieberman et al., 2001; Moreau et al., 2012; Nemes et al., 2015; H. J. Schneider et al., 2006).
Pituitary abnormality has been show to occur in one or more axes (Agha et al., 2004; Kelly et al., 2000; Klose et al., 2007; Kopczak et al., 2014; Lieberman et al., 2001; H. J. Schneider et al., 2006). However, there is no existing consensus as to which axis will be impacted or rendered impaired following an injury. For instance, impairments of GH was seen in 100% (n=10) of patients with isolated deficiency in one study (Klose et al., 2007), another study only reported it in 6% of patients (Lieberman et al., 2001). As well, Lieberman et al. (2001) reported that injury severity was not related to the number of affected pituitary axes.
Risk factors for anterior pituitary deficiencies following injury have been identified in a number of studies. Cuesta et al. (2016) reported that men with hypogonadism and women with menstrual dysfunction had more deficiency of various pituitary hormones than those without such conditions. Greater injury severity was found to be associated with post-injury hypopituitarism (Bondanelli et al., 2004; Klose et al., 2007; Nemes et al., 2015; Prasanna, Mittal, & Gandhi, 2015). In contrast, Tanriverdi et al. (2007) and Agha et al. (2004) did not find differences in pituitary dysfunction by injury severity. In other studies, high body mass index was found to be a risk factor for pituitary dysfunction (Klose et al., 2007; Ulfarsson et al., 2013). Further, Schneider et al. (2008) suggested that greater diffuse axonal injury and basal skull fracture are associated with a higher risk of pituitary impairment.
Outcomes of patients developing anterior pituitary dysfunction may be negatively impacted, whereby their ability to make good recovery post injury may be significantly reduced (Kelly et al., 2000). Marina et al. (2015) reported that Glasgow Outcome Scale (GOSE) and FIM scores at both 3 months and 1 year were associated with elevated stress hormones as well as suppressed thyroidal and gonadal hormones. Similarly, Prasanna et al. (2015) found that lower GOSE was associated with pituitary dysfunction, although Ulfarsson et al. (2013) did not find such results. As well, Rosario et al. (2013) reported that daily FIM gain was significantly lower in patients with hypopituitarism compared to those with normal function. However, the authors did not find any differences between those with and without endocrine function when comparing length of stay. Individuals with hypopituitarism have also been shown to have poorer Disability Rating Scores at discharge compared to those with normal function (Bondanelli et al.). Prodam et al. (2013) found that individuals with hypopituitarism had higher prevalence of dyslipidemia and altered glucose metabolism.
In a systematic review (n=66), Lauzier et al. (2014) reported the prevalence, predictors, and clinical outcomes of anterior pituitary disorders following TBI. In the long term, 31.6% (n=27) of individuals were found to have at least one disorder. Predictors of these disorders were age (RR=3.19; n=19), injury severity (RR=2.15; n=7), and skull fractures (RR=1.73; n=6). As well, anterior pituitary disorders were associated with increased ICU mortality (RR=1.79; n=4), but not Glasgow Outcome Scale score (n=3).
126.96.36.199 Growth Hormone Deficiency
Multiple findings suggest that higher BMI is associated with a higher incidence of post-injury GHD (Agha et al., 2004; Lieberman et al., 2001; H. J. Schneider et al., 2006; Fatih Tanriverdi et al., 2013). Other predictors of GHD include low IGF-1 levels (Agha, Phillips, et al., 2005; Agha et al., 2004; Bondanelli et al., 2007; Lieberman et al., 2001; Olivecrona et al., 2013; H. J. Schneider et al., 2006; Fatih Tanriverdi et al., 2013), older age (Bondanelli et al., 2004; H. J. Schneider et al., 2006), and more severe injury (Kleindienst, Brabant, Bock, Maser-Gluth, & Buchfelder, 2009; Fatih Tanriverdi et al., 2013). Conversely, other studies have not found GHD to be associated with BMI (Agha, Phillips, et al., 2005; Aimaretti et al., 2005; Bondanelli et al., 2004) or injury severity (Agha, Phillips, et al., 2005; Bondanelli et al., 2004).
The prevalence of post-injury GHD varies considerably across studies, ranging from 2.8% to 63.6% (Agha, Phillips, et al., 2005; Agha et al., 2004; Bondanelli et al., 2007; Bondanelli et al., 2004; Ghigo et al., 2005; Kelly et al., 2000; Kleindienst et al., 2009; Klose et al., 2007; Kopczak et al., 2014; Lieberman et al., 2001; Moreau et al., 2012; H. J. Schneider et al., 2006; F. Tanriverdi et al., 2007). As well, persistent deficiencies up to and beyond 12 months are commonly noted (Agha, Phillips, et al., 2005; Agha et al., 2004; Bondanelli et al., 2004; Ghigo et al., 2005; Kelly et al., 2000; Kleindienst et al., 2009; Lieberman et al., 2001; H. J. Schneider et al., 2006; Fatih Tanriverdi et al., 2013).
In patients with a confirmed GHD, GH replacement therapy has been recommended, and it is often administered subcutaneously (Auernhammer & Vlotides, 2007). The goal of therapy is to elevate serum IGF-I levels to at least the moderate range, which will vary depending on age and gender.
There is level 4 evidence that GH replacement therapy may be effective in treating GHD, fatigue, and depression post ABI.
188.8.131.52 Gonadotropic Deficiency
There is no consensus as to when to test for hypogonadism post injury. Due to uncertainty around the time when neuroendocrine disorders appear and disappear post injury, Hohl et al. (2009) suggested testing patients with TBI at least one year after injury for hypogonadism. Agha and Thompson (2005) suggested testing 3 to 6 months post injury, with follow-up testing at 12 months.
Gonadotropic deficiency (GD) is common among individuals with ABI, whereby acute prevalence rates range from 13% to 80% (Agha & Thompson, 2005; Aimaretti et al., 2005; Barton et al., 2016; Hohl et al., 2014; Kleindienst et al., 2009; Kopczak et al., 2014; Lee et al., 1994; Olivecrona et al., 2013; Rosario et al., 2013; H. J. Schneider et al., 2006; F. Tanriverdi et al., 2007). Persistent deficiencies up to and beyond 12 months have been commonly reported (Agha et al., 2004; Agha & Thompson, 2005; Aimaretti et al., 2005; Bondanelli et al., 2007; Bondanelli et al., 2004; Kelly et al., 2000; Kleindienst et al., 2009; Klose et al., 2007; Lieberman et al., 2001; Moreau et al., 2012; H. J. Schneider et al., 2006).
Common predictors of post-injury GD include older age (Agha et al., 2004), transient DI, polytrauma, hypoxia (M. Schneider et al.), and severe injury(Cernak, Savic, Lazarov, Joksimovic, & Markovic, 1999; Kleindienst et al., 2009). Several studies found that GD was associated with poor GCS scores (Agha & Thompson, 2005; Cernak et al., 1999; Kleindienst et al., 2009; H. J. Schneider et al., 2006), although other studies have not reported this relationship (Bondanelli et al., 2007; F. Tanriverdi et al., 2007). Compared to individuals with normal hormone functioning, GD was also found to be associated with poorer scores for the Functional Independence Measure, Disability Rating Scale, cognitive function (Barton et al., 2016; Bondanelli et al., 2007), and Glasgow Outcome Scale scores (Agha & Thompson, 2005; Barton et al., 2016). GD was also correlated with lower FIM gains per day (Rosario et al., 2013) and less clinical improvement on the modified Rankin Scale (H. J. Schneider et al., 2006). However, one study reported that the rate of GD did not differ between individuals who survived and did not survive (F. Tanriverdi et al., 2007).
Androgen Replacement in Men or Testosterone Therapy
Treatments for hypogonadism in men include oral testosterone replacement therapy, subcutaneous implantation (3-6 pellets of 200mg unmodified testosterone every 4-6 months), intramuscular injections (testosterone esters), transdermal patches and gels, and buccal delivery (Nieschlag et al., 2004). Although several treatments are available and there are several evidence-based guidelines on when and how to treat hypogonadism, there is no literature on the effectiveness of these treatments within the ABI population.
Estrogen Replacement in Women
Hormone replacement therapy in women has been shown to be effective during their menopausal or perimenopausal years. However, long-term treatment is not recommended due to the negative benefit-risk ratio (Auernhammer & Vlotides, 2007). Other treatments for women may include the administration of daily dehydroepiandrosterone or testosterone. Although some success has been found using these treatments, neither has been studied within the ABI population.
The rate of post-ABI hyperprolactinemia varies widely across studies, ranging from 5% to 50% (Agha, Phillips, et al., 2005; Aimaretti et al., 2005; Bondanelli et al., 2004; Kleindienst et al., 2009; Klose et al., 2007; Kopczak et al., 2014; Lieberman et al., 2001; Moreau et al., 2012; Olivecrona et al., 2013; H. J. Schneider et al., 2006; F. Tanriverdi et al., 2007). It is important to note, however, that the rate of post-injury hyperprolactinemia may be lower if patients receiving hyperprolactinemia-inducing drugs are excluded from the analysis (Kopczak et al., 2014; Lieberman et al., 2001; H. J. Schneider et al., 2006). Based on a limited number of studies, the rate of post-ABI hypoprolactinemia ranged from <1% to 8% (Bondanelli et al., 2004).
Post-injury hyperprolactinemia may persist up to 12 months post injury (Agha, Phillips, et al., 2005; Ghigo et al., 2005; Kleindienst et al., 2009; H. J. Schneider et al., 2006). However, it is difficult to predict whether individuals sustaining ABI will develop hyperprolactinemia. Agha et al. (2005; 2004) reported that post-injury hyperprolactinemia was not associated with factors such as age, sex, or GCS score; although a later study reported that GCS scores were negatively correlated to post-injury PRL levels (F. Tanriverdi et al., 2007). Given the apparent lack of association with negative outcomes, hyperprolactinemia may not be a significant deterrent to patient recovery (Olivecrona et al., 2013).
184.108.40.206 Adrenocorticotropic Hormone Deficiency
Findings from multiple studies suggest that ACTH (or cortisol) deficiency within 1 week of injury can vary considerably in rate, ranging from 8.8% to 78% (Hannon et al., 2013; Olivecrona et al., 2013). It is suggested that injury severity is an important predictor of ACTH deficiency, whereby more severe injuries are associated with more frequent or more profound ACTH deficiencies (Kleindienst et al., 2009; Fatih Tanriverdi et al., 2013; F. Tanriverdi et al., 2007). Other factors may include older age, injury to the basal skull, and lack of cranial vault fracture (M. Schneider et al., 2008). It has also been noted that women with menstrual dysfunction post ABI have significantly higher ACTH compared to those that have no menstrual dysfunction (Cuesta et al., 2016). However, there are inconsistencies as to whether these factors do in fact play a role in inciting post-injury corticotropic complications (Agha, Phillips, et al., 2005; Agha et al., 2004; Bondanelli et al., 2007; Olivecrona et al., 2013).
Individuals living with ABI may continue to demonstrate post-injury ACTH deficiency for up to 12 months (Ghigo et al., 2005) and beyond (Kleindienst et al., 2009; Fatih Tanriverdi et al., 2013). This may be problematic for recovery, as post-injury ACTH deficiency has been shown to be associated with poorer cognitive and physical outcomes (Moreau et al., 2012), as well as with other anterior pituitary disturbances such as hyperprolactinemia, low testosterone, and low tT3 and fT4 (Kleindienst et al., 2009), and higher mortality (Hannon et al., 2013). Further, there is a lack of known treatment options available to manage post-injury ACTH deficiencies.
220.127.116.11 Thyroid-Stimulating Hormone Deficiency
Diagnosing TSH deficiency has been shown to be more difficult, as the symptoms are often masked by other hormonal deficiencies post ABI. The treatment of TSH deficiency is often with levothyroxine (Yamada & Mori, 2008).
Multiple studies found that post-ABI TSH deficiency is uncommon, with very few individuals displaying symptoms at or greater than 6 months post injury (Agha, Phillips, et al., 2005; Agha et al., 2004; Bondanelli et al., 2007; Kelly et al., 2000; Klose et al., 2007). Impaired thyrotropic function is undesirable from a recovery standpoint, as a trend toward poor cognitive outcome was observed in individuals with thyrotropic dysfunctions (Moreau et al., 2012; Zetterling, Engstrom, Arnardottir, & Ronne-Engstrom, 2013).
Findings by Kleindienst et al. (2009) suggest that more severe injuries are associated with greater incidence of low TSH and fT4 levels, and thus post-injury thyrotropic complications. Earlier findings by Cernak et al. (1999) demonstrated that individuals with severe TBI had more profound thyrotropic disturbances than those with mild TBI. More specifically, those with severe TBI had decreased TSH levels for the entire duration of the study (7 days), whereas those with mild TBI showed an elevated TSH response for only a few days post injury. These findings are inconsistent with Tanriverdi et al. (2007), who reported that no significant differences in mean TSH levels were found among individuals with mild, moderate, and severe injuries. The discrepancy across studies indicates that there is still considerable uncertainty regarding predicting outcomes for those with post-injury thyrotropic complications (Moreau et al., 2012).
Growth hormone deficiency may be effectively treated with hormone replacement therapy and insulin growth like factor-1 therapy.
Progesterone may be effective in treating long-term outcomes in gonadotropic deficiency.
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9.1.1 Anatomy of the Pituitary Gland