Slow dissociation of partial agonists from the D₂ receptor is linked to reduced prolactin release

Combination of Haloperidol With UNC9994, β-arrestin-Biased Analog of Aripiprazole, Ameliorates Schizophrenia-Related Phenotypes Induced by NMDAR Deficit in Mice

BACKGROUND

Glutamatergic system dysfunction contributes to a full spectrum of schizophrenia-like symptoms, including the cognitive and negative symptoms that are resistant to treatment with antipsychotic drugs (APDs). Aripiprazole, an atypical APD, acts as a dopamine partial agonist, and its combination with haloperidol (a typical APD) has been suggested as a potential strategy to improve schizophrenia. Recently, an analog of aripiprazole, UNC9994, was developed. UNC9994 does not affect dopamine 2 receptor (D2R)-mediated Gi/o protein signaling but acts as a partial agonist for D2R/β-arrestin interactions. Hence, one of our objectives was to probe the behavioral effects of co-administrating haloperidol with UNC9994 in the N-methyl-D-aspartate receptor (NMDAR) mouse models of schizophrenia. The biochemical mechanisms underlying the neurobiological effects of dual haloperidol × UNC9994 action are currently missing. Hence, we aimed to explore D2R- and NMDAR-dependent signaling mechanisms that could underlie the effects of dual drug treatments.

METHODS

NMDAR hypofunction was induced pharmacologically by acute injection of MK-801 (NMDAR pore blocker; 0.15 mg/kg) and genetically by knockdown of Grin1 gene expression in mice, which have a 90% reduction in NMDAR levels (Grin1 knockdown [Grin1-KD]). After intraperitoneal injections of vehicle, haloperidol (0.15 mg/kg), UNC9994 (0.25 mg/kg), or their combination, mice were tested in open field, prepulse inhibition (PPI), Y-maze, and Puzzle box. Biochemical effects on the phosphorylation of Akt, glycogen synthase kinase-3 (GSK-3), and CaMKII in the prefrontal cortex (PFC) and striatum of MK-801-treated mice were assessed by western blotting.

RESULTS

Our findings indicate that low dose co-administration of UNC9994 and haloperidol reduces hyperactivity in MK-801-treated animals and in Grin1-KD mice. Furthermore, this dual administration effectively reverses PPI deficits, repetitive/rigid behavior in the Y-maze, and deficient executive function in the Puzzle box in both animal models. Pharmacological inhibition of NMDAR by MK-801 induced the opposite effects in the PFC and striatum on pAkt-S473 and pGSK3β-Ser9. Dual injection of haloperidol with UNC9994 reversed MK-801-induced effects on pAkt-S473 but not on pGSK3β-Ser9 in both brain structures.

CONCLUSIONS

The dual administration of haloperidol with UNC9994 at low doses represents a promising approach to ameliorate symptoms of schizophrenia. The combined drug regimen elicits synergistic effects specifically on pAkt-S473, suggesting it as a potential biomarker for antipsychotic actions.

Aripiprazole, a Novel Option in the Management of Restless Legs Syndrome (RLS) Patients with Augmentation and/or Severe RLS Symptoms: A Report of 4 Cases

Purpose

Restless Legs Syndrome (RLS) is a sensorimotor disorder associated with an unpleasant urge to move the limbs, relieved with movement, occurring in the evenings and with prolonged rest/inactivity. Treatment with dopamine agonists is effective for up to 60-90% of affected individuals. However, augmentation, ie, the paradoxical worsening of RLS symptoms after prolonged RLS treatment, is frequently reported, typically after 3-10 years of treatment. Here, we present 4 patients with RLS who were successfully treated with dopamine agonists but later developed augmentation. A trial of aripiprazole, a dopamine receptor partial agonist (DRPA), was initiated for treatment of augmentation symptoms.

Patients and Methods

Four patients treated for RLS with dopamine agonists developed augmentation. In each instance, augmentation symptoms did not respond adequately to a variety of medications including α2δ drugs, opioids or other agents. A trial of aripiprazole was initiated for each patient, and effects were evaluated.

Results

All four patients with severe RLS and augmentation with dopamine agonists achieved symptom control with aripiprazole. Patients endorsed 90-100% efficacy with aripiprazole by subjective self-report after failures with other agents. Further evaluation with the International Restless Legs Syndrome Study Group RLS Rating Scale (IRLS-SGRS) showed that benefits (from moderate to very severe, to mild to moderate severity) were largely maintained for 1-2 years. Aripiprazole doses to control augmentation symptoms were low (1-4 mg). No significant side effects were reported.

Conclusion

Aripiprazole may have utility for augmentation in RLS. We speculate that the partial agonist and antagonist properties of aripiprazole may limit potential for dopamine hyposensitization to progress to cause augmentation. Further research is needed to see if aripiprazole and/or other DRPAs are a viable long-term treatment option for patients experiencing augmentation and/or severe RLS with dopamine agonist therapy.

Pharmacodynamic model of slow reversible binding and its applications in pharmacokinetic/pharmacodynamic modeling: review and tutorial

Therapeutic responses of most drugs are initiated by the rate and degree of binding to their receptors or targets. The law of mass action describes the rate of drug-receptor complex association (k_on) and dissociation (k_off) where the ratio k_off/k_on is the equilibrium dissociation constant (K_d). Drugs with slow reversible binding (SRB) often demonstrate delayed onset and prolonged pharmacodynamic effects. This report reviews evidence for drugs with SRB features, describes previous pharmacokinetic/pharmacodynamic (PK/PD) modeling efforts of several such drugs, provides a tutorial on the mathematics and properties of SRB models, demonstrates applications of SRB models to additional compounds, and compares PK/PD fittings of SRB with other mechanistic models. We identified and summarized 52 drugs with in vitro-confirmed SRB from a PubMed literature search. Simulations with a SRB model and observed PK/PD profiles showed delayed and prolonged responses and that increasing doses/k_on or decreasing k_off led to greater expected maximum effects and a longer duration of effects. Recession slopes for return of responses to baseline after single doses were nearly linear with an inflection point that approaches a limiting value at larger doses. The SRB model newly captured literature data for the antihypertensive effects of candesartan and antiallergic effects of noberastine. Their PD profiles could also be fitted with indirect response and biophase models with minimal differences. The applicability of SRB models is probably commonplace, but underappreciated, owing to the need for in vitro confirmation of binding kinetics and the similarity of PK/PD profiles to models with other mechanistic determinants.

Immunoendocrine Peripheral Effects Induced by Atypical Antipsychotics

Atypical antipsychotics (AAP) or second-generation antipsychotics are the clinical option for schizophrenia treatment during acute psychoses, but they are also indicated for maintenance during lifetime, even though they are being used for other psychiatric conditions in clinical practice such as affective disorders and autism spectrum disorder, among others. These drugs are differentiated from typical antipsychotics based on their clinical profile and are a better choice because they cause fewer side effects regarding extrapyramidal symptoms (EPS). Even though they provide clear therapeutic benefits, AAP induce peripheral effects that trigger phenotypic, functional, and systemic changes outside the Central Nervous System (CNS). Metabolic disease is frequently associated with AAP and significantly impacts the patient's quality of life. However, other peripheral changes of clinical relevance are present during AAP treatment, such as alterations in the immune and endocrine systems as well as the intestinal microbiome. These less studied alterations also have a significant impact in the patient's health status. This manuscript aims to revise the peripheral immunological, endocrine, and intestinal microbiome changes induced by AAP consumption recommended in the clinical guidelines for schizophrenia and other psychiatric disorders.

Serum prolactin levels across pregnancy and the establishment of reference intervals

BACKGROUND

Reference intervals (RIs) play key roles in clinical diagnosis, treatment and prognosis. However, RIs for clinical testing tend to be confined to the general population, and RIs for pregnant women are not very comprehensive. In this study, we establish RIs for prolactin (PRL) in healthy pregnant and postpartum women in the Chinese population.

METHODS

Healthy pregnant women (n=378) were divided into groups according to whether they were in the first, second or third trimester of pregnancy. Healthy postpartum women (n=493) were separated into four groups according to mode of delivery as follows: postvaginal (24 and 48 h) or postcesarean (24 and 48 h). Healthy, non-pregnant women (n=123) were enrolled as a control group. Serum PRL levels were measured by electrochemiluminescence immunoassay, and RIs were established for each group.

RESULTS

The RIs for PRL were as follows: healthy non-pregnant women, 178.89-757.52 μIU/mL; first trimester, 621.20-3584.00 μIU/mL; second trimester, 1432.00-5349.68 μIU/mL; third trimester, 4087.33-9733.65 μIU/mL; 24 and 48 h postvaginal delivery (combined), 7865.36-10998.86 μIU/mL; and 24 and 48 h postcesarean delivery, 4556.41-7675.99 and 6578.45-9980.45 μIU/mL, respectively.

CONCLUSIONS

PRL RIs for pregnant women were established according to trimester, days postpartum and mode of delivery, thus providing a clinical reference for medical staff.

Effect of Brexpiprazole on Prolactin: An Analysis of Short- and Long-Term Studies in Schizophrenia

BACKGROUND

Hyperprolactinemia is an undesirable effect of most antipsychotics because of D2-receptor blockade. We assessed the effect of the D2-receptor partial agonist brexpiprazole on prolactin, based on pooled data from three 6-week, randomized, placebo-controlled studies and two open-label extension studies in patients with schizophrenia.

METHODS

In the short-term studies, patients received 0.25, 1, 2, 4 mg brexpiprazole or placebo; or flexible-dose brexpiprazole (2-4 mg/d), placebo, or active reference. The extension studies were 52-week, flexible-dose (1-4 mg/d) studies. We studied changes from baseline and shifts in prolactin status in patients with normal or elevated prolactin levels at baseline, and prolactin-related treatment-emergent adverse events (TEAEs).

RESULTS

Median changes from baseline to week 6 in brexpiprazole-treated patients in short-term studies were as follows: 3.63 ng/mL (females), 0.26 ng/mL (males); placebo: -2.15 ng/mL (females), -1.08 ng/mL (males).Median changes from baseline to week 52 in long-term studies were 0.60 ng/mL (females) and 0.18 ng/mL (males). Prolactin levels in patients with baseline values greater than 1× upper limit of normal tended to decrease over time regardless of previous treatment.The proportions of brexpiprazole-treated patients with greater than 3× upper limit of normal postbaseline prolactin values in short-term studies were as follows: 1.5% (females), 1.6% (males); placebo: 3.6% (females), 3.4% (males). Corresponding figures in long-term studies were 5.3% (females) and 2.0% (males).In short-term studies, the incidence of prolactin-related TEAEs was 1.8% for brexpiprazole and 0.6% for placebo. In long-term studies, the incidence of prolactin-related TEAEs was 1.7%.

CONCLUSIONS

Small changes in prolactin levels, low proportions of patients with postbaseline elevated prolactin values, and low incidence of prolactin-related TEAEs were observed after treatment with brexpiprazole.

Binding kinetics of cariprazine and aripiprazole at the dopamine D3 receptor

The dissociation behaviours of aripiprazole and cariprazine at the human D₂ and D₃ receptor are evaluated. A potential correlation between kinetics and in vivo profiles, especially cariprazine’s action on negative symptoms in schizophrenia, is investigated. The binding kinetics of four ligands were indirectly evaluated. After the receptor preparations were pre-incubated with the unlabelled ligands, the dissociation was initiated with an excess of [³H]spiperone. Slow dissociation kinetics characterizes aripiprazole and cariprazine at the D₂ receptor. At the D₃ receptor, aripiprazole exhibits a slow monophasic dissociation, while cariprazine displays a rapid biphasic behaviour. Functional ß-arrestin assays and molecular dynamics simulations at the D₃ receptor confirm a biphasic binding behaviour of cariprazine. This may influence its in vivo action, as the partial agonist could react rapidly to variations in the dopamine levels of schizophrenic patients and the ligand will not quantitatively dissociate from the receptor in one single step. With these findings novel agents may be developed that display rapid, biphasic dissociation from the D₃R to further investigate this effect on in vivo profiles.

Chronic Hypopituitarism Associated with Increased Postconcussive Symptoms Is Prevalent after Blast-Induced Mild Traumatic Brain Injury

The most frequent injury sustained by US service members deployed to Iraq or Afghanistan is mild traumatic brain injuries (mTBI), or concussion, by far most often caused by blast waves from improvised explosive devices or other explosive ordnance. TBI from all causes gives rise to chronic neuroendocrine disorders with an estimated prevalence of 25-50%. The current study expands upon our earlier finding that chronic pituitary gland dysfunction occurs with a similarly high frequency after blast-related concussions. We measured circulating hormone levels and accessed demographic and testing data from two groups of male veterans with hazardous duty experience in Iraq or Afghanistan. Veterans in the mTBI group had experienced one or more blast-related concussion. Members of the deployment control (DC) group encountered similar deployment conditions but had no history of blast-related mTBI. 12 of 39 (31%) of the mTBI participants and 3 of 20 (15%) veterans in the DC group screened positive for one or more neuroendocrine disorders. Positive screens for growth hormone deficiency occurred most often. Analysis of responses on self-report questionnaires revealed main effects of both mTBI and hypopituitarism on postconcussive and posttraumatic stress disorder (PTSD) symptoms. Symptoms associated with pituitary dysfunction overlap considerably with those of PTSD. They include cognitive deficiencies, mood and anxiety disorders, sleep problems, diminished quality of life, deleterious changes in metabolism and body composition, and increased cardiovascular mortality. When such symptoms are due to hypopituitarism, they may be alleviated by hormone replacement. These findings suggest consideration of routine post-deployment neuroendocrine screening of service members and veterans who have experienced blast-related mTBI and are reporting postconcussive symptoms.

Extrapyramidal side effects of antipsychotics are linked to their association kinetics at dopamine D2 receptors

Atypical antipsychotic drugs (APDs) have been hypothesized to show reduced extrapyramidal side effects (EPS) due to their rapid dissociation from the dopamine D₂ receptor. However, support for this hypothesis is limited to a relatively small number of observations made across several decades and under different experimental conditions. Here we show that association rates, but not dissociation rates, correlate with EPS. We measured the kinetic binding properties of a series of typical and atypical APDs in a novel time-resolved fluorescence resonance energy transfer assay, and correlated these properties with their EPS and prolactin-elevating liabilities at therapeutic doses. EPS are robustly predicted by a rebinding model that considers the microenvironment of postsynaptic D₂ receptors and integrates association and dissociation rates to calculate the net rate of reversal of receptor blockade. Thus, optimizing binding kinetics at the D₂ receptor may result in APDs with improved therapeutic profile.

Atypical antipsychotics show reduced extrapyramidal side effects compared to first generation drugs. Here the authors use time-resolved FRET to measure binding kinetics, and show that side effects correlate with drug association rates to the D₂ receptor, while dissociation rates correlate with prolactin elevation.

Safety, tolerability, and risks associated with first- and second-generation antipsychotics: a state-of-the-art clinical review

Since the discovery of chlorpromazine (CPZ) in 1952, first-generation antipsychotics (FGAs) have revolutionized psychiatric care in terms of facilitating discharge from hospital and enabling large numbers of patients with severe mental illness (SMI) to be treated in the community. Second-generation antipsychotics (SGAs) ushered in a progressive shift from the paternalistic management of SMI symptoms to a patient-centered approach, which emphasized targets important to patients - psychosocial functioning, quality of life, and recovery. These drugs are no longer limited to specific Diagnostic and Statistical Manual of Mental Disorders (DSM) categories. Evidence indicates that SGAs show an improved safety and tolerability profile compared with FGAs. The incidence of treatment-emergent extrapyramidal side effects is lower, and there is less impairment of cognitive function and treatment-related negative symptoms. However, treatment with SGAs has been associated with a wide range of untoward effects, among which treatment-emergent weight gain and metabolic abnormalities are of notable concern. The present clinical review aims to summarize the safety and tolerability profile of selected FGAs and SGAs and to link treatment-related adverse effects to the pharmacodynamic profile of each drug. Evidence, predominantly derived from systematic reviews, meta-analyses, and clinical trials of the drugs amisulpride, aripiprazole, asenapine, brexpiprazole, cariprazine, clozapine, iloperidone, lurasidone, olanzapine, paliperidone, quetiapine, risperidone, sertindole, ziprasidone, CPZ, haloperidol, loxapine, and perphenazine, is summarized. In addition, the safety and tolerability profiles of antipsychotics are discussed in the context of the "behavioral toxicity" conceptual framework, which considers the longitudinal course and the clinical and therapeutic consequences of treatment-emergent side effects. In SMI, SGAs with safer metabolic profiles should ideally be prescribed first. However, alongside with safety, efficacy should also be considered on a patient-tailored basis.

The role of kinetic context in apparent biased agonism at GPCRs

Biased agonism describes the ability of ligands to stabilize different conformations of a GPCR linked to distinct functional outcomes and offers the prospect of designing pathway-specific drugs that avoid on-target side effects. This mechanism is usually inferred from pharmacological data with the assumption that the confounding influences of observational (that is, assay dependent) and system (that is, cell background dependent) bias are excluded by experimental design and analysis. Here we reveal that ‘kinetic context', as determined by ligand-binding kinetics and the temporal pattern of receptor-signalling processes, can have a profound influence on the apparent bias of a series of agonists for the dopamine D₂ receptor and can even lead to reversals in the direction of bias. We propose that kinetic context must be acknowledged in the design and interpretation of studies of biased agonism.

Biased agonists act at a receptor to preferentially induce distinct intracellular signalling responses over others. Here the authors show how kinetics of ligand binding and signaling responses greatly influence observed bias profiles, and hence must be considered when studying biased agonists.

Adjunctive aripiprazole in risperidone-induced hyperprolactinaemia: double-blind, randomised, placebo-controlled trial

BACKGROUND

Hyperprolactinaemia is a troublesome side-effect of treatment with antipsychotics.

AIMS

This double-blind, placebo-controlled study aimed at examining the effect of adjunctive treatment with 10 mg aripiprazole on prolactin levels and sexual side-effects in patients with schizophrenia symptomatically maintained on risperidone.

METHOD

Thirty patients taking risperidone were enrolled into the trial (CTRI/2012/11/003114). Aripiprazole was administered at a fixed daily dose of 10 mg/day for 8 weeks. Serum prolactin was measured at baseline and at 8 weeks. Hyperprolactinaemia-related problems, psychopathology and side-effects were evaluated every 2 weeks.

RESULTS

Prolactin levels decreased by 58% in the aripiprazole group compared with an increase by 22% in the placebo group. Prolactin levels normalised in 46% of patients in the aripiprazole group (number needed to treat, NNT=2). Aripiprazole improved erectile dysfunction in five out of six patients. There were no significant differences in change in psychopathology or side-effects between groups.

CONCLUSIONS

Adjunctive aripiprazole reduced prolactin levels in those treated with risperidone, with no effect on psychopathology and extrapyramidal symptoms. This is a potential treatment for hyperprolactinaemia observed during treatment with second-generation antipsychotics.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2015. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

Hyperprolactinemia and medications for bipolar disorder: systematic review of a neglected issue in clinical practice

Drug-induced changes in serum prolactin (sPrl) levels constitute a relevant issue due to the potentially severe consequences on physical health of psychiatric patients such as sexual dysfunctions, osteoporosis and Prl-sensitive tumors. Several drugs have been associated to sPrl changes. Only antipsychotics have been extensively studied as sPrl-elevating agents in schizophrenia, but the extent to which bipolar disorder (BD) treatments affect sPrl levels is much less known. The objective of this systematic review is to summarize the evidence of the effects of drugs used in BD on Prl. This review followed the PRISMA statement. The MEDLINE/PubMed/Index Medicus, EMBASE, and Cochrane Library databases were systematically searched for articles in English appearing from any time to May 30, 2014. Twenty-six studies were included. These suggest that treatments for BD are less likely to be associated with Prl elevations, with valproate, quetiapine, lurasidone, mirtazapine, and bupropion reported not to change PRL levels significantly and lithium and aripiprazole to lower them in some studies. Taking into account the effects of the different classes of drugs on Prl may improve the care of BD patients requiring long-term pharmacotherapy. Based on the results of this review, lithium and valproate appear to be safer due to their low potential to elevate sPrL; among antipsychotics, quetiapine, lurasidone and aripiprazole appear to be similarly safe.

Paliperidone and aripiprazole differentially affect the strength of calcium-secretion coupling in female pituitary lactotrophs

Hyperprolactinemia is a common adverse in vivo effect of antipsychotic medications that are used in the treatment of patients with schizophrenia. Here, we compared the effects of two atypical antipsychotics, paliperidone and aripiprazole, on cAMP/calcium signaling and prolactin release in female rat pituitary lactotrophs in vitro. Dopamine inhibited spontaneous cAMP/calcium signaling and prolactin release. In the presence of dopamine, paliperidone rescued cAMP/calcium signaling and prolactin release in a concentration-dependent manner, whereas aripiprazole was only partially effective. In the absence of dopamine, paliperidone stimulated cAMP/calcium signaling and prolactin release, whereas aripiprazole inhibited signaling and secretion more potently but less effectively than dopamine. Forskolin-stimulated cAMP production was facilitated by paliperidone and inhibited by aripiprazole, although the latter was not as effective as dopamine. None of the compounds affected prolactin transcript activity, intracellular prolactin accumulation, or growth hormone secretion. These data indicate that paliperidone has dual hyperprolactinemic actions in lactotrophs i) by preserving the coupling of spontaneous electrical activity and prolactin secretion in the presence of dopamine and ii) by inhibiting intrinsic dopamine receptor activity in the absence of dopamine, leading to enhanced calcium signaling and secretion. In contrast, aripiprazole acts on prolactin secretion by attenuating, but not abolishing, calcium-secretion coupling.

The effects of novel and newly approved antipsychotics on serum prolactin levels: a comprehensive review

Since the 1970s, clinicians have increasingly become more familiar with hyperprolactinemia (HPRL) as a common adverse effect of antipsychotic medication, which remains the cornerstone of pharmacological treatment for patients with schizophrenia. Although treatment with second-generation antipsychotics (SGAs) as a group is, compared with use of the first-generation antipsychotics, associated with lower prolactin (PRL) plasma levels, the detailed effects on plasma PRL levels for each of these compounds in reports often remain incomplete or inaccurate. Moreover, at this moment, no review has been published about the effect of the newly approved antipsychotics asenapine, iloperidone and lurasidone on PRL levels. The objective of this review is to describe PRL physiology; PRL measurement; diagnosis, causes, consequences and mechanisms of HPRL; incidence figures of (new-onset) HPRL with SGAs and newly approved antipsychotics in adolescent and adult patients; and revisit lingering questions regarding this hormone. A literature search, using the MEDLINE database (1966-December 2013), was conducted to identify relevant publications to report on the state of the art of HPRL and to summarize the available evidence with respect to the propensity of the SGAs and the newly approved antipsychotics to elevate PRL levels. Our review shows that although HPRL usually is defined as a sustained level of PRL above the laboratory upper limit of normal, limit values show some degree of variability in clinical reports, making the interpretation and comparison of data across studies difficult. Moreover, many reports do not provide much or any data detailing the measurement of PRL. Although the highest rates of HPRL are consistently reported in association with amisulpride, risperidone and paliperidone, while aripiprazole and quetiapine have the most favorable profile with respect to this outcome, all SGAs can induce PRL elevations, especially at the beginning of treatment, and have the potential to cause new-onset HPRL. Considering the PRL-elevating propensity of the newly approved antipsychotics, evidence seems to indicate these agents have a PRL profile comparable to that of clozapine (asenapine and iloperidone), ziprasidone and olanzapine (lurasidone). PRL elevations with antipsychotic medication generally are dose dependant. However, antipsychotics having a high potential for PRL elevation (amisulpride, risperidone and paliperidone) can have a profound impact on PRL levels even at relatively low doses, while PRL levels with antipsychotics having a minimal effect on PRL, in most cases, can remain unchanged (quetiapine) or reduce (aripiprazole) over all dosages. Although tolerance and decreases in PRL values after long-term administration of PRL-elevating antipsychotics can occur, the elevations, in most cases, remain above the upper limit of normal. PRL profiles of antipsychotics in children and adolescents seem to be the same as in adults. The hyperprolactinemic effects of antipsychotic medication are mostly correlated with their affinity for dopamine D2 receptors at the level of the anterior pituitary lactotrophs (and probably other neurotransmitter mechanisms) and their blood-brain barrier penetrating capability. Even though antipsychotics are the most common cause of pharmacologically induced HPRL, recent research has shown that HPRL can be pre-existing in a substantial portion of antipsychotic-naïve patients with first-episode psychosis or at-risk mental state.

High prevalence of chronic pituitary and target-organ hormone abnormalities after blast-related mild traumatic brain injury

Studies of traumatic brain injury from all causes have found evidence of chronic hypopituitarism, defined by deficient production of one or more pituitary hormones at least 1 year after injury, in 25–50% of cases. Most studies found the occurrence of posttraumatic hypopituitarism (PTHP) to be unrelated to injury severity. Growth hormone deficiency (GHD) and hypogonadism were reported most frequently. Hypopituitarism, and in particular adult GHD, is associated with symptoms that resemble those of PTSD, including fatigue, anxiety, depression, irritability, insomnia, sexual dysfunction, cognitive deficiencies, and decreased quality of life. However, the prevalence of PTHP after blast-related mild TBI (mTBI), an extremely common injury in modern military operations, has not been characterized. We measured concentrations of 12 pituitary and target-organ hormones in two groups of male US Veterans of combat in Iraq or Afghanistan. One group consisted of participants with blast-related mTBI whose last blast exposure was at least 1 year prior to the study. The other consisted of Veterans with similar military deployment histories but without blast exposure. Eleven of 26, or 42% of participants with blast concussions were found to have abnormal hormone levels in one or more pituitary axes, a prevalence similar to that found in other forms of TBI. Five members of the mTBI group were found with markedly low age-adjusted insulin-like growth factor-I (IGF-I) levels indicative of probable GHD, and three had testosterone and gonadotropin concentrations consistent with hypogonadism. If symptoms characteristic of both PTHP and PTSD can be linked to pituitary dysfunction, they may be amenable to treatment with hormone replacement. Routine screening for chronic hypopituitarism after blast concussion shows promise for appropriately directing diagnostic and therapeutic decisions that otherwise may remain unconsidered and for markedly facilitating recovery and rehabilitation.