Prevalence of testosterone deficiency after spinal cord injury. PM R. 2011;3:929-932. [PMID: 22024324 DOI: 10.1016/j.pmrj.2011.07.008]

Sex-specific alterations in functional connectivity and network topology in patients with degenerative cervical myelopathy

Patients with degenerative cervical myelopathy (DCM) experience structural and functional brain reorganization. However, few studies have investigated the influence of sex on cerebral alterations. The present study investigates the role of sex on brain functional connectivity (FC) and global network topology in DCM and healthy controls (HCs). The resting-state functional MRI data was acquired for 100 patients (58 males vs. 42 females). ROI-to-ROI FC and network topological features were characterized for each patient and HC. Group differences in FC and network topological features were examined. Compared to healthy counterparts, DCM males exhibited higher FC between vision-related brain regions, and cerebellum, brainstem, and thalamus, but lower FC between the intracalcarine cortex and frontal and somatosensory cortices, while DCM females demonstrated higher FC between the thalamus and cerebellar and sensorimotor regions, but lower FC between sensorimotor and visual regions. DCM males displayed higher FC within the cerebellum and between the posterior cingulate cortex (PCC) and vision-related regions, while DCM females displayed higher FC between frontal regions and the PCC, cerebellum, and visual regions. Additionally, DCM males displayed significantly greater intra-network connectivity and efficiency compared to healthy counterparts. Results from the present study imply sex-specific supraspinal functional alterations occur in patients with DCM.

Evaluating Sex Steroid Hormone Neuroprotection in Spinal Cord Injury in Animal Models: Is It Promising in the Clinic?

The primary mechanism of traumatic spinal cord injury (SCI) comprises the initial mechanical trauma due to the transmission of energy to the spinal cord, subsequent deformity, and persistent compression. The secondary mechanism of injury, which involves structures that remained undamaged after the initial trauma, triggers alterations in microvascular perfusion, the liberation of free radicals and neurotransmitters, lipid peroxidation, alteration in ionic concentrations, and the consequent cell death by necrosis and apoptosis. Research in the treatment of SCI has sought to develop early therapeutic interventions that mitigate the effects of these pathophysiological mechanisms. Clinical and experimental evidence has demonstrated the therapeutic benefits of sex-steroid hormone administration after traumatic brain injury and SCI. The administration of estradiol, progesterone, and testosterone has been associated with neuroprotective effects, better neurological recovery, and decreased mortality after SCI. This review evaluated evidence supporting hormone-related neuroprotection over SCI and the possible underlying mechanisms in animal models. As neuroprotection has been associated with signaling pathways, the effects of these hormones are observed on astrocytes and microglia, modulating the inflammatory response, cerebral blood flow, and metabolism, mediating glutamate excitotoxicity, and their antioxidant effects. Based on the current evidence, it is essential to analyze the benefit of sex steroid hormone therapy in the clinical management of patients with SCI.

Lived Experiences of Sexuality and Sexual Functioning in Males with SCI: A Mixed-Methods Study

Background

Sexual dysfunction is highly prevalent in males with spinal cord injury (SCI) and has been recognized to be a key recovery priority.

Objectives

This cross-sectional, mixed-methods study aimed to investigate the major themes linked to sexual functioning in males with chronic (>1 year) SCI.

Methods

Twenty male participants with SCI, aged 25 to 59 years, completed validated questionnaires exploring sexual function/satisfaction and health-related quality of life and a semi-structured interview with an experienced sexual medicine physician. Sex hormone concentrations and metabolic biomarkers, along with body composition and habitual physical activity levels, were assessed. Interview recordings were transcribed and thematic analysis performed using combined COM-B (Capability, Opportunity, Motivation, and Behavior) and biopsychosocial models to identify and organize major contributors and barriers to sexual functioning.

Results

Metabolic and hormonal biomarkers largely fell within normal physiological ranges despite reduced sexual functioning reported in our cohort (19/20 participants reported some degree of erectile dysfunction). Qualitative analysis of interview transcripts revealed 24 themes. Adaptability was important for improving sexual satisfaction. Attraction and attentiveness to sex and partners remained stable over time, while the desire for intimacy increased post injury. Sexual social norms, and comparisons to the able-bodied population, provided challenges for sexual activity and partnership. Environmental concerns regarding access to sexual health resources and accessible physical spaces during intimacy were relevant. Mood disorders and general life stressors negatively impacted sexual desire, while physical activity encouraged sexual activity.

Conclusion

By considering a holistic view of sexuality in males with SCI, we identified key contributors and barriers to sexual functioning for the cohort studied.

Prevalence of opioid use in adults with spinal cord injury: A systematic review and meta-analysis

OBJECTIVE

To determine the prevalence, reported harms and factors associated with opioid use among adults with spinal cord injury (SCI) living in the community.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

Comprehensive literature searches were conducted in PubMed (MEDLINE), EMBASE, CINAHL, Web of Science and Scopus for articles published between 2000 and 2023. Risk of bias was assessed using a prevalence-specific tool. Random-effects meta-analyses were conducted to pool prevalence data for any context of opioids. Sensitivity and subgroup analyses were also performed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the study protocol was registered via Prospero (CRD42022350768).

RESULTS

Of the 4969 potential studies, 38 were included in the review. Fifty-three percent of studies had a low risk of bias, with a high risk of bias in 5% of studies. The pooled prevalence for the 38 studies included in the meta-analysis (total cohort size of 50,473) across any opioid context was 39% (95% confidence interval [CI], 32-47). High heterogeneity was evident, with a prediction interval twice as wide as the 95% CI (prediction interval, 7-84%). Mean or median opioid dose was unreported in 95% of studies. Opioid dose and factors related to opioids were also rarely explored in the SCI populations.

CONCLUSIONS

Results should be interpreted with caution based on the high heterogeneity and imprecise pooled prevalence of opioids. Contextual details including pain, cohort-specific injury characteristics and opioid dosage were inconsistently reported, indicating a clear need for additional studies in a population at greater risk of experiencing opioid-related adverse effects.

Nitric oxide-induced lipophagic defects contribute to testosterone deficiency in rats with spinal cord injury

Introduction

Males with acute spinal cord injury (SCI) frequently exhibit testosterone deficiency and reproductive dysfunction. While such incidence rates are high in chronic patients, the underlying mechanisms remain elusive.

Methods and results

Herein, we generated a rat SCI model, which recapitulated complications in human males, including low testosterone levels and spermatogenic disorders. Proteomics analyses showed that the differentially expressed proteins were mostly enriched in lipid metabolism and steroid metabolism and biosynthesis. In SCI rats, we observed that testicular nitric oxide (NO) levels were elevated and lipid droplet-autophagosome co-localization in testicular interstitial cells was decreased. We hypothesized that NO impaired lipophagy in Leydig cells (LCs) to disrupt testosterone biosynthesis and spermatogenesis. As postulated, exogenous NO donor (S-nitroso-N-acetylpenicillamine (SNAP)) treatment markedly raised NO levels and disturbed lipophagy via the AMPK/mTOR/ULK1 pathway, and ultimately impaired testosterone production in mouse LCs. However, such alterations were not fully observed when cells were treated with an endogenous NO donor (L-arginine), suggesting that mouse LCs were devoid of an endogenous NO-production system. Alternatively, activated (M1) macrophages were predominant NO sources, as inducible NO synthase inhibition attenuated lipophagic defects and testosterone insufficiency in LCs in a macrophage-LC co-culture system. In scavenging NO (2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO)) we effectively restored lipophagy and testosterone levels both in vitro and in vivo, and importantly, spermatogenesis in vivo. Autophagy activation by LYN-1604 also promoted lipid degradation and testosterone synthesis.

Discussion

In summary, we showed that NO-disrupted-lipophagy caused testosterone deficiency following SCI, and NO clearance or autophagy activation could be effective in preventing reproductive dysfunction in males with SCI.

A comprehensive look at the psychoneuroimmunoendocrinology of spinal cord injury and its progression: mechanisms and clinical opportunities

Spinal cord injury (SCI) is a devastating and disabling medical condition generally caused by a traumatic event (primary injury). This initial trauma is accompanied by a set of biological mechanisms directed to ameliorate neural damage but also exacerbate initial damage (secondary injury). The alterations that occur in the spinal cord have not only local but also systemic consequences and virtually all organs and tissues of the body incur important changes after SCI, explaining the progression and detrimental consequences related to this condition. Psychoneuroimmunoendocrinology (PNIE) is a growing area of research aiming to integrate and explore the interactions among the different systems that compose the human organism, considering the mind and the body as a whole. The initial traumatic event and the consequent neurological disruption trigger immune, endocrine, and multisystem dysfunction, which in turn affect the patient's psyche and well-being. In the present review, we will explore the most important local and systemic consequences of SCI from a PNIE perspective, defining the changes occurring in each system and how all these mechanisms are interconnected. Finally, potential clinical approaches derived from this knowledge will also be collectively presented with the aim to develop integrative therapies to maximize the clinical management of these patients.

Early Changes in Androgen Levels in Individuals with Spinal Cord Injury: A Longitudinal SwiSCI Study

We aimed to explore longitudinal changes in androgen levels in individuals with spinal cord injury (SCI) within initial inpatient rehabilitation stay and identify clinical/injury characteristics associated with hormone levels. Linear regression analysis was applied to explore the association between personal/injury characteristics and androgen hormones (total testosterone, free testosterone, sex hormone-binding globulin (SHBG), dehydroepiandrosterone (DHEA), and dehydroepiandrosterone sulfate (DHEA-S)) at admission to rehabilitation. Longitudinal changes in androgen levels were studied using linear mixed models. Analyses were stratified by sex and by injury type. We included 70 men and 16 women with SCI. We observed a non-linear association between age, time since injury, and androgens at baseline. At admission to initial rehabilitation, mature serum SHBG (full-length, protein form which lacks the N-terminal signaling peptide) was higher, while DHEA and DHEA-S were lower among opioid users vs. non-users. Serum levels of total testosterone and DHEA-S increased over rehabilitation period [β 3.96 (95%CI 1.37, 6.56), p = 0.003] and [β 1.77 (95%CI 0.73, 2.81), p = 0.01], respectively. We observed no significant changes in other androgens. Restricting our analysis to men with traumatic injury did not materially change our findings. During first inpatient rehabilitation over a median follow up of 5.6 months, we observed an increase in total testosterone and DHEA-S in men with SCI. Future studies need to explore whether these hormonal changes influence neurological and functional recovery as well as metabolic parameters during initial rehabilitation stay.

Energy expenditure and nutrient intake after spinal cord injury: a comprehensive review and practical recommendations

Many persons with spinal cord injury (SCI) have one or more preventable chronic diseases related to excessive energetic intake and poor eating patterns. Appropriate nutrient consumption relative to need becomes a concern despite authoritative dietary recommendations from around the world. These recommendations were developed for the non-disabled population and do not account for the injury-induced changes in body composition, hypometabolic rate, hormonal dysregulation and nutrition status after SCI. Because evidence-based dietary reference intake values for SCI do not exist, ensuring appropriate consumption of macronutrient and micronutrients for their energy requirements becomes a challenge. In this compressive review, we briefly evaluate aspects of energy balance and appetite control relative to SCI. We report on the evidence regarding energy expenditure, nutrient intake and their relationship after SCI. We compare these data with several established nutritional guidelines from American Heart Association, Australian Dietary Guidelines, Dietary Guidelines for Americans, Institute of Medicine Dietary Reference Intake, Public Health England Government Dietary Recommendations, WHO Healthy Diet and the Paralyzed Veterans of America (PVA) Clinical Practice Guidelines. We also provide practical assessment and nutritional recommendations to facilitate a healthy dietary pattern after SCI. Because of a lack of strong SCI research, there are currently limited dietary recommendations outside of the PVA guidelines that capture the unique nutrient needs after SCI. Future multicentre clinical trials are needed to develop comprehensive, evidence-based dietary reference values specific for persons with SCI across the care continuum that rely on accurate, individual assessment of energy need.

Testosterone Treatment As a Function-Promoting Therapy in Sarcopenia Associated with Aging and Chronic Disease

Sarcopenia is characterized by loss of muscle strength and physical ability because of aging and/or chronic disease. Supplemental testosterone and other androgenic-anabolic steroids have been investigated as countermeasures to ameliorate the negative consequences of sarcopenia; these trials show dose-related improvements in lean body mass, maximal voluntary strength, stair climbing power, aerobic capacity, hemoglobin, and self-reported function, but less consistent improvements in walking speed. Randomized clinical trials with large cohorts and patient-important outcome measures are needed to determine long-term efficacy and safety of testosterone treatment in improving physical function and reducing physical disability, falls, and fractures in older adults with sarcopenia.

Experiences of patients and their partners with sexual problems after spinal cord injury: A phenomenological qualitative study

Objective: This study aimed to examine the experiences of patients and their partners about their sexual lives after Spinal Cord Injury (SCI).Design: This qualitative study was based on Heidegger's hermeneutic phenomenological approach.Setting: The Physical Medicine and Rehabilitation Outpatient Clinic of a city hospital in the Central Anatolia Region in Turkey.Participants: The study consisted of seven female and six male patients with spinal cord injury and their partners.Outcome measures: The textual analysis was carried out in three stages: (1) a naive reading, (2) a structural analysis, and (3) a comprehensive understanding of the text including a discussion. The sample size was calculated by using the criterion sampling technique.Results: As a result of the in-depth interviews with individuals with SCI about their sexual experiences, five themes were derived: (1) first confrontation with SCI, (2) experienced sexual problems, (3) coping, (4) partners' views on sexual problems, and (5) other people.Conclusion: It was found that the sex life of individuals with SCI was negatively affected, they were left helpless in dealing with their problems, and that some patients had difficulties in coping with this condition.

Visceral Adiposity, Inflammation, and Testosterone Predict Skeletal Muscle Mitochondrial Mass and Activity in Chronic Spinal Cord Injury

Background

Mitochondrial health is an important predictor of several health-related comorbidities including obesity, type 2 diabetes mellitus, and cardiovascular disease. In persons with spinal cord injury (SCI), mitochondrial health has been linked to several important body composition and metabolic parameters. However, the complex interplay of how mitochondrial health is affected has yet to be determined in this population.

Objective

In this study, we examined the contribution of visceral adiposity, inflammatory biomarkers, testosterone and circulating serum growth factors as predictors of mitochondrial health in persons with chronic SCI.

Participants

Thirty-three individuals with chronic SCI (n = 27 Males, n = 6 Females, age: 40 ± 13.26 years, level of injury: C4-L1, BMI: 23 ± 5.57) participated in this cross-sectional study.

Methods

Visceral adipose tissue (VAT) was measured via magnetic resonance imaging (MRI). After an overnight fast, serum testosterone, inflammatory biomarkers [interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), c-reactive protein (CRP)], and anabolic growth factors [insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 3 (IGFBP-3)] were measured. Skeletal muscle biopsies were obtained from the vastus lateralis muscle to measure citrate synthase (CS) and Complex III activity. Regression analyses were used to examine predictors of mitochondrial mass and activity.

Results

CS activity was negatively associated with VAT (r² = 0.360, p < 0.001), CRP (r² = 0.168, p = 0.047), and positively associated with testosterone (r² = 0.145, p = 0.042). Complex III activity was negatively associated with VAT relative to total lean mass (VAT:TLM) (r² = 0.169, p = 0.033), trended for CRP (r² = 0.142, p = 0.069), and positively associated with testosterone (r² = 0.224, p = 0.010). Multiple regression showed CS activity was significantly associated with VAT + CRP (r² = 0.412, p = 0.008) and VAT + Testosterone (r² = 0.433, p = 0.001). Complex III activity was significantly associated with VAT relative to total trunk cross-sectional area (CSA) + CRP (VAT:total trunk CSA + CRP; r² = 0.286, p = 0.048) and VAT + Testosterone (r² = 0.277, p = 0.024).

Conclusion

Increased visceral adiposity and associated inflammatory signaling (CRP) along with reduced testosterone levels predict mitochondrial dysfunction following SCI. Specifically, lower VAT_CSA and higher testosterone levels or lower VAT_CSA and lower CRP levels positively predict mitochondrial mass and enzyme activity in persons with chronic SCI. Future research should investigate the efficacy of diet, exercise, and potentially testosterone replacement therapy on enhancing mitochondrial health in chronic SCI.

Clinical Trial Registration

[www.ClinicalTrials.gov], identifier: [NCT02660073].

Sex-Dependent Cortical Volume Changes in Patients with Degenerative Cervical Myelopathy

Degenerative cervical myelopathy (DCM) is a progressive condition characterized by degeneration of osseocartilaginous structures within the cervical spine resulting in compression of the spinal cord and presentation of clinical symptoms. Compared to healthy controls (HCs), studies have shown DCM patients experience structural and functional reorganization in the brain; however, sex-dependent cortical differences in DCM patients remains largely unexplored. In the present study, we investigate the role of sex differences on the structure of the cerebral cortex in DCM and determine how structural differences may relate to clinical measures of neurological function. T1-weighted structural MRI scans were acquired in 85 symptomatic and asymptomatic patients with DCM and 90 age-matched HCs. Modified Japanese Orthopedic Association (mJOA) scores were obtained for patients. A general linear model was used to determine vertex-level significant differences in gray matter volume (GMV) between the following groups (1) male HCs and female HCs, (2) male patients and female patients, (3) male patients and male HCs, and (4) female patients and female HCs. Within patients, males exhibited larger GMV in motor, language, and vision related brain regions compared to female DCM patients. Males demonstrated a significant positive correlation between GMV and mJOA score, in which patients with worsening neurological symptoms exhibited decreasing GMV primarily across somatosensory and motor related cortical regions. Females exhibited a similar association, albeit across a broader range of cortical areas including those involved in pain processing. In sensorimotor regions, female patients consistently showed smaller GMV compared with male patients, independent of mJOA score. Results from the current study suggest strong sex-related differences in cortical volume in patients with DCM, which may reflect hormonal influence or differing compensation mechanisms.

Spinal Cord Injury Reduces Serum Levels of Fibroblast Growth Factor-21 and Impairs Its Signaling Pathways in Liver and Adipose Tissue in Mice

Spinal cord injury (SCI) results in dysregulation of carbohydrate and lipid metabolism; the underlying cellular and physiological mechanisms remain unclear. Fibroblast growth factor 21 (FGF21) is a circulating protein primarily secreted by the liver that lowers blood glucose levels, corrects abnormal lipid profiles, and mitigates non-alcoholic fatty liver disease. FGF21 acts via activating FGF receptor 1 and ß-klotho in adipose tissue and stimulating release of adiponectin from adipose tissue which in turn signals in the liver and skeletal muscle. We examined FGF21/adiponectin signaling after spinal cord transection in mice fed a high fat diet (HFD) or a standard mouse chow. Tissues were collected at 84 days after spinal cord transection or a sham SCI surgery. SCI reduced serum FGF21 levels and hepatic FGF21 expression, as well as β-klotho and FGF receptor-1 (FGFR1) mRNA expression in adipose tissue. SCI also reduced serum levels and adipose tissue mRNA expression of adiponectin and leptin, two major adipokines. In addition, SCI suppressed hepatic type 2 adiponectin receptor (AdipoR2) mRNA expression and PPARα activation in the liver. Post-SCI mice fed a HFD had further suppression of serum FGF21 levels and hepatic FGF21 expression. Elevated serum free fatty acid (FFA) levels after HFD feeding were observed in post-SCI mice but not in sham-mice, suggesting defective FFA uptake after SCI. Moreover, after SCI several genes that are implicated in insulin's action had reduced expression in tissues of interest. These findings suggest that downregulated FGF21/adiponectin signaling and impaired responsiveness of adipose tissues to FGF21 may, at least in part, contribute to the overall picture of metabolic dysfunction after SCI.

Role of exercise on visceral adiposity after spinal cord injury: a cardiometabolic risk factor

PURPOSE

Visceral adipose tissue (VAT) is associated with cardiometabolic disease risk in able-bodied (AB) populations. However, the underlying mechanisms of VAT-induced disease risk are unknown in persons with spinal cord injury (SCI). Potential mechanisms of VAT-induced cardiometabolic dysfunction in persons with SCI include systemic inflammation, liver adiposity, mitochondrial dysfunction, and anabolic deficiency. Moreover, how exercise interventions impact these mechanisms associated with VAT-induced cardiometabolic dysfunction are still being explored.

METHODS

A search for relevant scientific literature about the effects of exercise on VAT and cardiometabolic health was conducted on the PubMed database. Literature from reference lists was also included when appropriate.

RESULTS

Both aerobic and resistance exercise training beneficially impact health and VAT mass via improving mitochondrial function, glucose effectiveness, and inflammatory signaling in SCI and AB populations. Specifically, aerobic exercise appears to also modulate cellular senescence in AB populations and animal models, while resistance exercise seems to augment anabolic signaling in persons with SCI.

CONCLUSIONS

The current evidence supports regular engagement in exercise to reduce VAT mass and the adverse effects on cardiometabolic health in persons with SCI. Future research is needed to further elucidate the precise mechanisms by which VAT negatively impacts health following SCI. This will likely facilitate the development of rehabilitation protocols that target VAT reduction in persons with SCI.

Mechanical Medical Device for Generating Vibration and Stimulation of the Neuron Pathways

This article describes a medical device uses precisely generated vibrations to obtain genetic material (sperm) in injured men, tetraplegics, and paraplegics. A significant advantage is the absence of general anesthesia of the patient. The DC motor of a medical device works with a safe voltage powered by rechargeable or AA cells. The principle of generation of vibration is a crank mechanism. Rotation of the flywheel is converted to rectilinear reciprocating motion. The amplitude is set in the range between 1–4 mm and the frequency is controlled by the RPM of the DC motor. If the stimulation will be followed preciously with the methodology, the process will be completed within 12 min from the beginning of stimulation. The success rate of the device is in the range between 65–85% depending on the patient’s condition and the extent of the spinal cord lesion. The measurement of sinusoidal oscillations was performed by using a stand in which the device was mounted. The amplitude was measured with an accelerometer and then mathematically converted by software Matlab and MS-Excel to the magnitude of the deviation in mm. Measurements have shown that the proposed design meets the requirements for amplitude and frequency.

Endocrine Therapy for the Functional Recovery of Spinal Cord Injury

Spinal cord injury (SCI) is a major cause of physical disability and leads to patient dissatisfaction with their quality of life. Patients with SCI usually exhibit severe clinical symptoms, including sensory and motor dysfunction below the injured levels, paraplegia, quadriplegia and urinary retention, which can exacerbate the substantial medical and social burdens. The major pathological change observed in SCI is inflammatory reaction, which induces demyelination, axonal degeneration, and the apoptosis and necrosis of neurons. Traditional medical treatments are mainly focused on the recovery of motor function and prevention of complications. To date, numerous studies have been conducted to explore the cellular and molecular mechanism of SCI and have proposed lots of effective treatments, but the clinical applications are still limited due to the complex pathogenesis and poor prognosis after SCI. Endocrine hormones are kinds of molecules that are synthesized by specialized endocrine organs and can participate in the regulation of multiple physiological activities, and their protective effects on several disorders have been widely discussed. In addition, many studies have identified that endocrine hormones can promote nerve regeneration and functional recovery in individuals with central nervous system diseases. Therefore, studies investigating the clinical applications of endocrine hormones as treatments for SCI are necessary. In this review, we described the neuroprotective roles of several endocrine hormones in SCI; endocrine hormone administration reduces cell death and promotes functional repair after SCI. We also proposed novel therapies for SCI.

Testosterone, level of the lesion and age are independently associated with prostate volume in men with chronic spinal cord injury

PURPOSE

Although men with spinal cord injury (SCI) exhibit a prostate volume significantly smaller compared to age-matched able-bodied men, the independent association of lower prostate volume with its putative determinants has never been analyzed in this population. This study was designed to identify variables independently associated with prostate volume in men with chronic SCI.

METHODS

In this cross-sectional study, prostate volume of 138 men with chronic (> 1 years) SCI, aged 54.5 (25th-75th percentile: 36.0-66.0) years, was evaluated with trans-rectal ultrasonography. All patients underwent a complete neurological exam, as well as biochemical and hormonal assessment, including total testosterone (TT) levels. Free testosterone levels were calculated (cFT) by the Vermeulen formula.

RESULTS

The median prostate volume was 23.4 mL. At the univariate analysis, a larger prostate volume was associated with higher TT (p = 0.00001) and cFT (p = 0.001), SCI level below T12 (p = 0.007), more advanced age (p = 0.04), lower body mass index (p = 0.04), higher functional independence score (p = 0.06), higher values of prostate-specific antigen (p = 0.12) and shorter duration of the injury (p = 0.21). However, at the multiple regression analyses, an independent and positive association only persisted between the prostate volume with either TT or cFT levels, and, to a lesser extent, with age and a level of spinal lesion below T12. A prostate volume below the median value was observed in 91.4% (32/35) of patients with both androgen deficiency (TT < 264 ng/dL) and spinal lesion level ≥ T12, but only in 16.5% (2/12) of patients with both normal androgen levels and spinal lesion level below T12 (p < 0.001).

CONCLUSIONS

Our data indicate that lower testosterone levels and, to a lesser extent, a younger age and a spinal lesion level ≥ T12 represent the only variables exhibiting an independent association with a smaller prostate volume in men with SCI.

Considerations for Studying Sex as a Biological Variable in Spinal Cord Injury

In response to NIH initiatives to investigate sex as a biological variable in preclinical animal studies, researchers have increased their focus on male and female differences in neurotrauma. Inclusion of both sexes when modeling neurotrauma is leading to the identification of novel areas for therapeutic and scientific exploitation. Here, we review the organizational and activational effects of sex hormones on recovery from injury and how these changes impact the long-term health of spinal cord injury (SCI) patients. When determining how sex affects SCI it remains imperative to expand outcomes beyond locomotor recovery and consider other complications plaguing the quality of life of patients with SCI. Interestingly, the SCI field predominately utilizes female rodents for basic science research which contrasts most other male-biased research fields. We discuss the unique caveats this creates to the translatability of preclinical research in the SCI field. We also review current clinical and preclinical data examining sex as biological variable in SCI. Further, we report how technical considerations such as housing, size, care management, and age, confound the interpretation of sex-specific effects in animal studies of SCI. We have uncovered novel findings regarding how age differentially affects mortality and injury-induced anemia in males and females after SCI, and further identified estrus cycle dysfunction in mice after injury. Emerging concepts underlying sexually dimorphic responses to therapy are also discussed. Through a combination of literature review and primary research observations we present a practical guide for considering and incorporating sex as biological variable in preclinical neurotrauma studies.

Independent Association of Erectile Dysfunction and Low Testosterone Levels With Life Dissatisfaction in Men With Chronic Spinal Cord Injury

BACKGROUND

The loss of global functional independence, along with bladder, bowel, and sexual dysfunctions, may contribute to psychological distress and life dissatisfaction after spinal cord injury (SCI).

AIM

To explore the relationship of erectile function and androgenic status with life satisfaction, independently from confounders recognizable in spinal cord-injured men.

METHODS

100 consecutive men (49 ± 17 years) admitted to a rehabilitation program because of chronic SCI (≥1 year) underwent clinical/biochemical evaluations, including the assessment of life and sexual satisfaction using the Life-Satisfaction Questionnaire-9 (LiSat-9), erectile function using the International Index of Erectile Function-5 (IIEF-5), global and bowel-bladder functional independence using the Spinal Cord Independence Measure (SCIM) and measurement of total testosterone (TT) levels. The free testosterone level was calculated using the Vermeulen formula.

OUTCOMES

The outcomes include the relationship between sexual health and life satisfaction in men with SCI.

RESULTS

A LiSat-9 score <4, suggestive for life dissatisfaction, was exhibited by 49% of men. When compared with the life-satisfied group, a significantly higher percentage of them had sexual dissatisfaction and erectile dysfunction (ED); they also exhibited significantly lower levels of TT and calculated free testosterone (cFT) and a more severe impairment of bowel-bladder function. The life satisfaction degree correlated with sexual satisfaction degree, IIEF-5 score, TT, cFT, and bowel-bladder function degree. At the logistic regression model, including sexual LiSat-9 subscore and bowel-bladder SCIM subscore, only the former exhibited a significant negative association with life dissatisfaction. In a further logistic regression model, including the putative key determinants of sexual satisfaction, erectile function, and cFT levels, a higher odd of life dissatisfaction was independently associated both with a lower IIEF-5 score (OR: 0.93; 95% CI: 0.88, 0.98) and lower cFT levels (OR: 0.98; 95% CI: 0.98, 0.99).

CLINICAL IMPLICATIONS

In men with chronic SCI, assessment of erectile function and testosterone levels can help to predict life satisfaction.

STRENGTHS & LIMITATIONS

This is the first demonstration of the independent association of androgen deficiency and ED with life satisfaction in men with SCI. Prospective studies are warranted to clarify the cause-effect relationships.

CONCLUSIONS

In men with SCI, ED and low testosterone levels exhibit a significant independent association with life dissatisfaction; longitudinal intervention studies could explore possible effects of their treatment in improving sexual and life satisfaction in this population. D'Andrea S, Minaldi E, Castellini C, et al. Independent Association of Erectile Dysfunction and Low Testosterone Levels With Life Dissatisfaction in Men With Chronic Spinal Cord Injury. J Sex Med 2020;17:911-918.

Testosterone and Resistance Training Improve Muscle Quality in Spinal Cord Injury

PURPOSE

Spinal cord injury (SCI) negatively impacts muscle quality and testosterone levels. Resistance training (RT) has been shown to increase muscle cross-sectional area (CSA) after SCI, whereas testosterone replacement therapy (TRT) has been shown to improve muscle quality in other populations. The purpose of this pilot study was to examine if the combined effects of these interventions, TRT + RT, may maximize the beneficial effects on muscle quality after SCI.

METHODS

Twenty-two SCI subjects randomized into either a TRT + RT (n = 11) or TRT (n = 11) intervention for 16 wk. Muscle quality measured by peak torque (PT) at speeds of 0°·s (PT-0°), 60°·s (PT-60°), 90°·s (PT-90°), and 180°·s (PT-180°), knee extensor CSA, specific tension, and contractile speed (rise time [RTi], and half-time to relaxation [½TiR]) was assessed for each limb at baseline and postintervention using 2 × 2 mixed models.

RESULTS

After 16 wk, subjects in the TRT + RT group increased PT-0° (48.4%, P = 0.017), knee extensor CSA (30.8%, P < 0.0001), and RTi (17.7%, P = 0.012); with no significant changes observed in the TRT group. Regardless of the intervention, changes to PT-60° (28.4%, P = 0.020), PT-90° (26.1%, P = 0.055), and PT-180° (20.6%, P = 0.09) for each group were similar.

CONCLUSIONS

The addition of mechanical stress via RT to TRT maximizes improvements to muscle quality after complete SCI when compared with TRT administered alone. Our evidence shows that this intervention increases muscle size and strength while also improving muscle contractile properties.

Lifestyle modifications and pharmacological approaches to improve sexual function and satisfaction in men with spinal cord injury: a narrative review

STUDY DESIGN

A narrative review describing various components of sexual dysfunction in men with spinal cord injury (SCI), as well as addressing potential therapeutic approaches.

OBJECTIVES

Restoration of sexual function is considered one of the most important health priorities for individuals with SCI. The purpose of this review is to provide information regarding the factors that are less appreciated when considering changes to sexual function in men with SCI. We also propose therapeutic approaches, with a focus on lifestyle modifications, which have been shown to improve sexual function.

METHODS

A literature search was performed and limited evidence for therapeutic approaches in individuals with SCI was supplemented by consistent findings from the able-bodied population.

RESULTS

We evaluated the less addressed factors known to contribute to sexual dysfunction in men with SCI, including hormonal influences (i.e., testosterone deficiency, thyroid hormone, and cortisol), psychological factors (i.e., pain, fatigue, depression, and body image), and secondary SCI complications (i.e., urinary tract infection, pressure sores, and autonomic dysreflexia). To address these factors beyond standard medical treatments for sexual dysfunction, options include physical activity/exercise, diet, and specific medications for symptom relief (i.e., testosterone replacement therapy and selective serotonin reuptake inhibitors for depression).

CONCLUSIONS

Physical activity's potential application, efficacy across multiple aspects of sexuality, and the lack of side effects, suggests that long-term exercise is a viable solution to directly or indirectly improve sexual function in males with SCI. Diet and supplemental medications may further promote body composition changes, which more broadly affect sexuality.

Risk of prostate cancer in men with spinal cord injury: A systematic review and meta-analysis

A lower risk of prostate cancer has been reported in men with spinal cord injury (SCI) as compared to that observed in able-bodied subjects. As injury-related consequences can have opposite effects on prostate pathophysiology, this meta-analysis aimed to (1) establish the existence/quantify the extent of decreased prostate cancer risk following SCI and (2) find out if there is any statistically significant difference in prostate-specific antigen (PSA) levels between SCI and able-bodied subjects. MEDLINE, Cochrane Library, Scopus, CINAHL, and ScienceDirect databases were used. Only studies reporting a prostate cancer diagnosis and/or PSA levels following SCI and in able-bodied controls were included. Five studies provided information about prostate cancer on 35 293 subjects with SCI and 158 140 controls. Six studies were included in PSA analysis which reported information on 391 men with SCI and 1921 controls. Pooled estimates indicated that SCI reduced the prostate cancer risk by approximately 50% as compared to controls, whereas differences in PSA levels were not statistically significant. Funnel plots suggested the presence of publication bias only in PSA analysis. Between-study heterogeneity was established and when, according to meta-regression models, analysis was restricted to studies including men with mean age over 55 years, prostate cancer risk in SCI decreased up to 65.0% than that in controls with no heterogeneity (P = 0.33, I² = 9%). In conclusion, in men over 55 years old, SCI decreases the prostate cancer risk up to 65.0% than that in controls. The large between-study heterogeneity on PSA confirms its poor reliability as a screening tool for prostate cancer in SCI.

Dietary manipulation and testosterone replacement therapy may explain changes in body composition after spinal cord injury: A retrospective case report

BACKGROUND

Reduced level of physical activity, high-fat diet and skeletal muscle atrophy are key factors that are likely to contribute to deleterious changes in body composition and metabolic following spinal cord injury (SCI). Reduced caloric intake with lowering percentage macronutrients of fat and increasing protein intake may likely to improve body composition parameters and decrease ectopic adiposity after SCI.

AIM

To highlight the effects of dietary manipulation and testosterone replacement therapy (TRT) on body composition after SCI

METHODS

A 31-year-old male with T5 SCI was administered transdermal TRT daily for 16 wk. Caloric intake and percentage macronutrients were analyzed using dietary recalls. Magnetic resonance imaging and dual-energy x-ray absorptiometry were used to measure changes in body composition.

RESULTS

Caloric intake and fat percentage were reduced by 445 kcal/d and 6.5%, respectively. Total body weight decreased by 8%, body fat decreased by 29%, and lean mass increased by 7%. Thigh subcutaneous adipose tissue cross-sectional area was reduced by 31%.

CONCLUSION

Manipulation of caloric intake, fat percentage, and protein percentage may have influenced body composition after SCI.

Activity-Based Training Alters Penile Reflex Responses in a Rat Model of Spinal Cord Injury

INTRODUCTION

Multisystem functional gains have been reported in males with spinal cord injury (SCI) after undergoing activity-based training (ABT), including increases in scoring of sexual function and reports of improved erectile function.

AIM

This study aims to examine the effect of daily 60-minute locomotor training and exercise in general on sexual function in a rat SCI contusion model.

METHODS

Male Wistar rats received a T9 contusion SCI. Animals were randomized into 4 groups: a quadrupedal stepping group (SCI + QT), a forelimb-only exercise group (SCI + FT), a non-trained harnessed group (SCI + NT), and a home cage non-trained group (SCI + HC). The 2 non-trained groups were combined (SCI) post hoc. Daily training sessions were 60 minutes in duration for 8 weeks. Urine samples were collected during bi-weekly 24-hour metabolic cage behavioral testing. Latency, numbers of penile dorsiflexion, and glans cupping were recorded during bi-weekly penile dorsiflexion reflex (PDFR) testing. Terminal electromyography (EMG) recordings of the bulbospongiosus muscle (BSM) were recorded in response to stimulation of the dorsal nerve of the penis (DNP).

OUTCOMES

ABT after SCI had a significant effect on PDFR, as well as BSM EMG latency and burst duration.

RESULTS

SCI causes a significant decrease in the latency to onset of PDFR. After 8 weeks of ABT, SCI + QT animals had a significantly increased latency relative to the post-SCI baseline. BSM EMG response to DNP stimulation had a significantly decreased latency and increase in average and maximum amplitude in SCI + QT animals. SCI animals had a significantly longer burst duration than trained animals. Time between PDFR events, penile dorsiflexion, glans cupping, and urine testosterone were not affected by ABT.

CLINICAL IMPLICATIONS

ABT has a positive influence on sexual function and provides a potential therapy to enhance the efficacy of current sexual dysfunction therapies in the male SCI population.

STRENGTHS AND LIMITATIONS

Several significant small improvements in sexual function were found in a clinically relevant rat model of SCI using a readily available rehabilitative therapy. The limited findings could reflect insensitivity of the PDFR as a measure of erectile function.

CONCLUSIONS

These results indicate that task-specific stepping and/or loading provide sensory input to the spinal cord impacting the neural circuitry responsible for sexual function. Steadman CJ, Hoey RF, Montgomery LR, et al. Activity-Based Training Alters Penile Reflex Responses in a Rat Model of Spinal Cord Injury. J Sex Med 2019; 16:1143-1154.

Correlation between thyroid function, testosterone levels, and depressive symptoms in females with spinal cord injury

Study Design

Prospective case series.

Objective

Investigate the association of testosterone and thyroid-stimulating hormone (TSH) levels with depressive symptoms in women after spinal cord injury (SCI).

Setting

Community SCI clinic.

Methods

Twenty-seven participants were enrolled in this study. Total testosterone (Total T) and TSH levels as well as the Center for Epidemiological Studies Depression Scale (CES-D) survey and monthly sexual activity were obtained from only 20 participants. Pearson's correlations were used to assess the relationship between age, time from injury, Total T level, TSH level, and CES-D total score. Follow-up analyses investigating the role of monthly sexual activity was also explored.

Results

Participants' average age and time from injury was 44.4 ± 12.7 years old and 11.7 ± 8.89 years, respectively. Low Total T was observed in four participants and one of those participant's presented with low TSH as well. Nine women were classified as "at risk for clinical depression" on the CES-D (total score >15). Pearson's correlations revealed a significant association between time from injury and TSH (r = .536, p = .015), as well as CES-D total score (r = -.547, p = .013). Total T was associated with CES-D total score (ρ = -.541, p = .02).

Conclusions

This study provides preliminary results on abnormal hormone levels and depressive symptoms in women after SCI. Twenty percent of this sample presented with low Total T, which was associated with increased depressive symptoms after accounting for time from injury. Further research is needed to investigate the impact of SCI on hormone function and mental health in women post SCI.

Sponsorship

Sally Rynne National Association of Women's Health Quality Award 2002.

B Cell-Activating Factor Is Associated with Testosterone and Smoking Status in Non-Ambulatory Men with Chronic Spinal Cord Injury

B cell-mediated autoimmunity may contribute to poor neurological outcomes after spinal cord injury (SCI). B cell-activating factor (BAFF) is a key cytokine involved in B cell development, proliferation, activation, and survival whose expression is elevated in men with chronic SCI. The aim of this study was to assess factors associated with circulating BAFF in non-ambulatory males with chronic SCI. We assessed the association between clinical and demographic factors, health habits, and circulating BAFF levels in a convenience sample of 43 non-ambulatory men with chronic spinal cord injury (≥ 1 year post-injury). Serum BAFF and total testosterone levels were quantified by enzyme-linked immunosorbent assay. Body composition was determined by whole body dual-energy X-ray absorptiometry. In multivariable models, active smokers had significantly greater BAFF levels than former/nonsmokers (871 pg/mL vs. 665 pg/ml, p = 0.002). BAFF decreased 36 ± 11.1 pg/mL for every 1 ng/mL increase in total testosterone (p = 0.002). This model explained 41% of the variation in circulating BAFF levels (model p < 0.0001). Our findings suggest that modifiable health habits may be associated with elevated BAFF levels in men with non-ambulatory chronic SCI. Further, the significant and independent negative association between testosterone levels and BAFF would suggest a link between androgen deficiency and autoimmunity observed in SCI via modulation of BAFF and B cell numbers. This points toward BAFF as a potential biomarker of injury severity and a target of therapies designed to reduce neuroinflammation and improve neurological outcomes after SCI.

Can the positive association of osteocalcin with testosterone be unmasked when the preeminent hypothalamic-pituitary regulation of testosterone production is impaired? The model of spinal cord injury

PURPOSE

Osteocalcin (OCN), released from the bone matrix during the resorption phase, in its undercarboxylated form, stimulates testosterone (T) biosynthesis in mouse and a loss-of-function mutation of its receptor was associated with hypergonadotropic hypogonadism in humans. Nevertheless, when population-based studies have explored the OCN-T association, conflicting results have been reported. Hypothesizing that the evidence of a positive association between OCN and T could have been hindered by the preeminent role of a well-functioning hypothalamus-pituitary axis in promoting T biosynthesis, we explored this association in men with chronic spinal cord injury (SCI), exhibiting high prevalence of non-hypergonadotropic androgen deficiency.

METHODS

Fifty-five consecutive men with chronic SCI underwent clinical/biochemical evaluations, including measurements of total T (TT), OCN and 25(OH)D levels. Free T (FT) levels were calculated by the Vermeulen formula. Comorbidity was scored by Charlson comorbidity index (CCI).

RESULTS

A biochemical androgen deficiency (TT < 300 ng/dL) was observed in 15 patients (27.3%). TT was positively correlated with OCN, 25(OH)D and leisure time physical activity and negatively correlated with age, BMI and CCI. OCN was also positively correlated with calculated FT and negatively correlated with BMI and HOMA-IR. At the multiple linear regression analyses, a positive association of OCN with TT and calculated FT persisted after adjustment for confounders.

CONCLUSIONS

The positive association here found between OCN and T levels in men with chronic SCI reinforces the notion that a bone-testis axis is also functioning in humans and suggests that it can be unmasked when the preeminent hypothalamic-pituitary regulation of T production is impaired.

Body composition changes with testosterone replacement therapy following spinal cord injury and aging: A mini review

Context Hypogonadism is a male clinical condition in which the body does not produce enough testosterone. Testosterone plays a key role in maintaining body composition, bone mineral density, sexual function, mood, erythropoiesis, cognition and quality of life. Hypogonadism can occur due to several underlying pathologies during aging and in men with physical disabilities, such as spinal cord injury (SCI). This condition is often under diagnosed and as a result, symptoms undertreated. Methods In this mini-review, we propose that testosterone replacement therapy (TRT) may be a viable strategy to improve lean body mass (LBM) and fat mass (FM) in men with SCI. Evidence Synthesis Supplementing the limited data from SCI cohorts with consistent findings from studies in non-disabled aging men, we present evidence that, relative to placebo, transdermal TRT can increase LBM and reduce FM over 3-36 months. The impact of TRT on bone mineral density and metabolism is also discussed, with particular relevance for persons with SCI. Moreover, the risks of TRT remain controversial and pertinent safety considerations related to transdermal administration are outlined. Conclusion Further research is necessary to help develop clinical guidelines for the specific dose and duration of TRT in persons with SCI. Therefore, we call for more high-quality randomized controlled trials to examine the efficacy and safety of TRT in this population, which experiences an increased risk of cardiometabolic diseases as a result of deleterious body composition changes after injury.

Spinal cord injury and male infertility-a review of current literature, knowledge gaps, and future research

Spinal cord injury (SCI) affects nearly half a million new patients worldwide, with 17,700 in the US each year, and disproportionately impacts young males of reproductive age. Almost every aspect of male reproduction is affected by SCI, resulting in: erectile, endocrine and sexual dysfunction, decreased sperm motility despite an often-normal count, and abnormal semen emission and ejaculation. The aim of this review is to focus on how SCI impacts testicular spermatogenesis, sperm function, semen quality, and overall fecundity while discussing what is not known, and future avenues for research.

Fertility and sexuality in the spinal cord injury patient

BACKGROUND

After a spinal cord injury, patients have different perceptions of sexuality, sexual function, and potential for fertility. These changes can greatly impact quality of life over a lifetime.

PURPOSE

The purpose of this workgroup was to identify common evidence based or expert opinion themes and recommendations regarding treatment of sexuality, sexual function and fertility in the spinal cord injury population.

METHODS

As part of the SIU-ICUD joint consultation of Urologic Management of the Spinal Cord Injury (SCI), a workgroup and comprehensive literature search of English language manuscripts regarding fertility and sexuality in the spinal cord injury patient were formed. Articles were compiled, and recommendations in the chapter are based on group discussion and follow the Oxford Centre for Evidence-based Medicine system for levels of evidence (LOEs) and grades of recommendation (GORs).

RESULTS

Genital arousal, ejaculation, and orgasm are significantly impacted after spinal cord injury in both male and female SCI patients. This may have a more significant impact on potential for fertility in male spinal cord injury patients, particularly regarding ability of generate erection, semen quantity and quality. Female patients should be consulted that pregnancy is still possible after injury and a woman should expect resumption of normal reproductive function. As a result, sexual health teaching should be continued in women despite injury. Pregnancy in a SCI may cause complications such as autonomic dysreflexia, so this group should be carefully followed during pregnancy.

CONCLUSIONS

By understanding physiologic changes after injury, patients and care teams can work together to achieve goals and maximize sexual quality of life after the injury.

Activity-Based Physical Rehabilitation with Adjuvant Testosterone to Promote Neuromuscular Recovery after Spinal Cord Injury

Neuromuscular impairment and reduced musculoskeletal integrity are hallmarks of spinal cord injury (SCI) that hinder locomotor recovery. These impairments are precipitated by the neurological insult and resulting disuse, which has stimulated interest in activity-based physical rehabilitation therapies (ABTs) that promote neuromuscular plasticity after SCI. However, ABT efficacy declines as SCI severity increases. Additionally, many men with SCI exhibit low testosterone, which may exacerbate neuromusculoskeletal impairment. Incorporating testosterone adjuvant to ABTs may improve musculoskeletal recovery and neuroplasticity because androgens attenuate muscle loss and the slow-to-fast muscle fiber-type transition after SCI, in a manner independent from mechanical strain, and promote motoneuron survival. These neuromusculoskeletal benefits are promising, although testosterone alone produces only limited functional improvement in rodent SCI models. In this review, we discuss the (1) molecular deficits underlying muscle loss after SCI; (2) independent influences of testosterone and locomotor training on neuromuscular function and musculoskeletal integrity post-SCI; (3) hormonal and molecular mechanisms underlying the therapeutic efficacy of these strategies; and (4) evidence supporting a multimodal strategy involving ABT with adjuvant testosterone, as a potential means to promote more comprehensive neuromusculoskeletal recovery than either strategy alone.

Relationship Between Gonadal Function and Cardiometabolic Risk in Young Men With Chronic Spinal Cord Injury

BACKGROUND

We reported previously that young men with chronic spinal cord injury (SCI) have a greater prevalence of testosterone deficiency compared with an age-matched, healthy control population. Young men with SCI also are at increased risk for developing cardiometabolic dysfunction after injury. It is unclear whether testosterone deficiency is associated with heightened cardiometabolic risk in men with SCI.

OBJECTIVE

To investigate associations among levels of testosterone in young men with chronic SCI and surrogate markers of cardiometabolic risk.

DESIGN

Secondary cross-sectional analysis.

SETTING

Rehabilitation research centers in Washington, DC, and Miami, Florida.

PARTICIPANTS

Men (n = 58) aged 18-45 years with chronic (≥1 year), motor complete SCI without comorbidities or use of testosterone therapy.

METHODS

Plasma concentrations of testosterone, lipids, inflammatory markers (C-reactive protein and interleukin-6), percent hemoglobin A1c, glucose, and insulin were measured in a fasting state using standard assays. A 2-hour oral glucose tolerance test and Framingham Risk Score were assessed for each subject. Body composition was assessed by dual X-ray absorptiometry scan.

MAIN OUTCOME MEASUREMENTS

Surrogate markers of cardiometabolic risk among men based on the level of total testosterone (TT; ≤300, 301-500, or >500 ng/dL) and free testosterone (fT; ≤9 or >9 ng/dL). Comparisons were made between men with normal and low TT or fT.

RESULTS

Framingham Risk Score was significantly greater in men with low fT (P < .05). Percent body fat (P < .05) and waist-to-hip ratio (P < .05) but not body mass index (P > .08), were greater in men with low TT or low fT. Men with low TT or low fT had lower high-density lipoprotein cholesterol levels (P < .05) without differences in fasting triglycerides (P > .1) or low-density lipoprotein cholesterol (P > .07). Men with low TT had greater levels of inflammatory markers C-reactive protein (P < .05) and interleukin-6 (P < .05). Men with low TT or low fT had greater fasting glucose (P < .05) and greater insulin resistance (P < .04), without differences in percent hemoglobin A1c (P > .8).

CONCLUSIONS

In young men with chronic SCI who undergo an accelerated aging process postinjury, hypogonadism is associated with an unfavorable cardiometabolic risk profile. Further research is needed to determine whether a causal relationship exists between hypogonadism and heightened cardiometabolic risk in men with SCI and whether routine screening for testosterone deficiency is warranted in this population.

LEVEL OF EVIDENCE

IV.

Administration of increasing doses of gonadotropin-releasing hormone in men with spinal cord injury to investigate dysfunction of the hypothalamic-pituitary-gonadal axis

STUDY DESIGN

Prospective.

OBJECTIVES

To determine the optimum gonadotropin-releasing hormone (GnRH) dose to identify dysfunction of the hypothalamic-pituitary-gonadal axis in men with spinal cord injury (SCI).

SETTING

Metropolitan Area Hospitals, New York and New Jersey, USA.

METHODS

SCI men (16 hypogonadal (HG = serum testosterone <12.1 nmol/l) and 14 eugonadal (EG)) and able-bodied (AB) men (27 HG and 11 EG) were studied. GnRH (10, 50, and 100 μg) was randomly administered intravenously on three separate visits. Blood samples were collected post-GnRH for serum-luteinizing hormone (LH) and follicular-stimulating hormone (FSH).

RESULTS

HG and EG men had a similar proportion of clinically acceptable gonadotropin responses to all three GnRH doses. The incremental gonadotropin responses to GnRH were not significantly different across the groups. However, in the SCI-HG group, GnRH of 100 μg resulted in the greatest integrated FSH response, and in the SCI-EG group, GnRH of 50 μg resulted in the greatest integrated LH response compared with the AB groups. A consistent, but not significant, absolute increase in gonadotropin release was observed in the SCI groups at all GnRH doses.

CONCLUSIONS

Lower doses of GnRH did not improve the ability to identify the clinical dysfunction of the hypothalamic-pituitary-gonadal axis. However, the absolutely higher SCI-HG FSH response to GnRH of 100 μg and a higher SCI-EG LH response to GnRH of 50 μg, along with a higher gonadotropin release at all GnRH doses, albeit not significant, suggests a hypothalamic-pituitary dysfunction in persons with SCI.

Effect of Testosterone on TRPV1 Expression in a Model of Orofacial Myositis Pain in the Rat

Recent clinical studies have revealed sex differences in response to transient receptor potential vanilloid 1 (TRPV1) agonist-induced pain. However, the mechanism of these differences in TRPV1-related chronic pain remains unclear. In the present study, we investigate the effects of inflammation and gonadal hormones on TRPV1 expression in trigeminal ganglia. Inflammatory pain was modeled by injecting complete Freund's adjuvant (CFA) into the left masseter muscle in rats. TRPV1 mRNA and protein levels in the trigeminal ganglia of male and female rats following CFA injection were assessed. CFA-induced changes in TRPV1 mRNA and protein expression in the trigeminal ganglia from orchidectomized (ODX) male rats and testosterone-replaced ODX rats were examined. Additionally, TRPV1 mRNA levels in the trigeminal ganglia from ovariectomized (OVX) female and ODX male rats treated with tamoxifen were assessed. We found that the levels of TRPV1 mRNA and protein in the trigeminal ganglia from female rats following CFA injection were significantly higher than in the ganglia from naïve female rats. CFA-induced inflammatory hyperalgesia did not alter TRPV1 expression in the trigeminal ganglia from male rats. The TRPV1 mRNA and protein expression levels in the ODX male trigeminal ganglia were significantly upregulated on day 3 following the initiation of inflammation. However, CFA-induced inflammatory pain had no significant effect on TRPV1 mRNA or protein expression in testosterone-replaced ODX rats. Furthermore, tamoxifen was unable to inhibit the upregulation of TRPV1 expression in OVX female and ODX male rats after CFA injection. In summary, these data indicate that gender differences in TRPV1 function may be, in part, mediated by sex-dependent TRPV1 expression in sensory ganglia. Testosterone plays a key role in the inhibition of TRPV1 expression in this rat chronic inflammatory pain model.

Liver Adiposity and Metabolic Profile in Individuals with Chronic Spinal Cord Injury

PURPOSE

To quantify liver adiposity using magnetic resonance imaging (MRI) and to determine its association with metabolic profile in men with spinal cord injury (SCI).

MATERIALS AND METHODS

MRI analysis of liver adiposity by fat signal fraction (FSF) and visceral adipose tissue (VAT) was completed on twenty participants. Intravenous glucose tolerance test was conducted to measure glucose effectiveness (S_g) and insulin sensitivity (S_i). Lipid panel, fasting glucose, glycated hemoglobin (HbA1c), and inflammatory cytokines were also analyzed.

RESULTS

Average hepatic FSF was 3.7% ± 2.1. FSF was positively related to TG, non-HDL-C, fasting glucose, HbA1c, VAT, and tumor necrosis factor alpha (TNF-α). FSF was negatively related to S_i and testosterone. FSF was positively related to VAT (r = 0.48, p = 0.032) and TNF-α (r = 0.51, p = 0.016) independent of age, level of injury (LOI), and time since injury (TSI). The associations between FSF and metabolic profile were independent of VAT.

CONCLUSIONS

MRI noninvasively estimated hepatic adiposity in men with chronic SCI. FSF was associated with dysfunction in metabolic profile, central adiposity, and inflammation. Importantly, liver adiposity influenced metabolic profile independently of VAT. These findings highlight the significance of quantifying liver adiposity after SCI to attenuate the development of metabolic disorders.

Gender Dimorphism in Central Adiposity May Explain Metabolic Dysfunction After Spinal Cord Injury

BACKGROUND

Increase in visceral adipose tissue (VAT) is an independent risk for mortality and other health-related comorbidities.

OBJECTIVE

To examine the gender differences in VAT and subcutaneous adipose tissue (SAT) cross-sectional areas (CSA) between men and women with chronic spinal cord injury (SCI). The differences in the distribution of central adiposity were used to determine the association of VAT and SAT to metabolic dysfunction after SCI.

DESIGN

Cross-sectional design.

SETTING

Hospital-based study.

PARTICIPANTS

Sixteen individuals (8 men and 8 women) with motor complete SCI were matched based on age, time since injury, and level of injury.

METHODS

Anthropometrics, dual x-ray absorptiometry (DXA), and magnetic resonance imaging were captured to measure lean mass, fat mass (FM), percentage FM, VAT, and SAT CSAs. Basal metabolic rate was measured, and intravenous glucose tolerance test and lipid panel were performed.

MAIN OUTCOME MEASUREMENTS

VAT, SAT, and metabolic profile.

RESULTS

SAT CSA was 1.6 -1.75 times greater in the upper and lower trunks in women compared to men with SCI (P < .05). VAT CSA was 1.8-2.6 times greater in the upper and lower trunks in men compared to women with SCI (P < .05). VAT adjusted to body weight was greater in men compared to women with SCI. High-density lipoprotein cholesterol (HDL-C) was positively related to SAT and negatively related to VAT. Glucose effectiveness was negatively related to lower trunk SAT (r = -0.60, P = .02). HDL-C ratio and triglycerides were positively related to upper VAT, lower VAT, and VAT:SAT ratio.

CONCLUSION

Magnetic resonance imaging demonstrated that there is a gender dimorphism in central adiposity in persons with chronic SCI. This gender dimorphism in central adipose tissue distribution may explain the higher prevalence of metabolic dysfunction in men with SCI, especially, the decrease in the HDL-C profile.

LEVEL OF EVIDENCE

IV.

Testicular responses to hCG stimulation at varying doses in men with spinal cord injury

STUDY DESIGN

Prospective.

OBJECTIVES

To test whether provocative stimulation of the testes identifies men with chronic spinal cord injury (SCI), a population in which serum testosterone concentrations are often depressed, possibly due to gonadal dysfunction. To accomplish this objective, conventional and lower than the conventional doses of human chorionic gonadotropin (hCG) were administered.

METHODS

Thirty men with chronic SCI (duration of injury >1 year; 18 and 65 years old; 16 eugonadal (>12.1 nmol l-1) and 14 hypogonadal (⩽12.1 nmol l-1)) or able-bodied (AB) men (11 eugonadal and 27 hypogonadal) were recruited for the study. Stimulation tests were performed to quantify testicular responses to the intramuscular administration of hCG at three dose concentrations (ithat is, 400, 2000 and 4000 IU). The hCG was administered on two consecutive days, and blood was collected for serum testosterone in the early morning prior to each of the two injections; subjects returned on day 3 for a final blood sample collection.

RESULTS

The average gonadal response in the SCI and AB groups to each dose of hCG was not significantly different in the hypogonadal or eugonadal subjects, with the mean serum testosterone concentrations in all groups demonstrating an adequate response.

CONCLUSIONS

This work confirmed the absence of primary testicular dysfunction without additional benefit demonstrated of provocative stimulation of the testes with lower than conventional doses of hCG. Our findings support prior work that suggested a secondary testicular dysfunction that occurs in a majority of those with SCI and depressed serum testosterone concentrations.

Salivary alpha amylase not chromogranin A reflects sympathetic activity: exercise responses in elite male wheelchair athletes with or without cervical spinal cord injury

Background

Salivary alpha amylase (sAA) and chromogranin A (sCgA) have both been suggested as non-invasive markers for sympathetic nervous system (SNS) activity. A complete cervical spinal cord injury leading to tetraplegia is accompanied with sympathetic dysfunction; the aim of this study was to establish the exercise response of these markers in this in vivo model.

Methods

Twenty-six elite male wheelchair athletes (C6–C7 tetraplegia: N = 8, T6–L1 paraplegia: N = 10 and non-spinal cord injured controls: N = 8) performed treadmill exercise to exhaustion. Saliva and blood samples were taken pre, post and 30 min post exercise and analysed for sAA, sCgA and plasma adrenaline concentration, respectively.

Results

In all three subgroups, sAA and sCgA were elevated post exercise (P < 0.05). Whilst sCgA was not different between subgroups, a group × time interaction for sAA explained the reduced post-exercise sAA activity in tetraplegia (162 ± 127 vs 313 ± 99 (paraplegia) and 328 ± 131 U mL⁻¹ (controls), P = 0.005). The post-exercise increase in adrenaline was not apparent in tetraplegia (P = 0.74). A significant correlation was found between adrenaline and sAA (r = 0.60, P = 0.01), but not between adrenaline and sCgA (r = 0.06, P = 0.79).

Conclusions

The blunted post-exercise rise in sAA and adrenaline in tetraplegia implies that both reflect SNS activity to some degree. It is questionable whether sCgA should be used as a marker for SNS activity, both due to the exercise response which is not different between the subgroups and its non-significant relationship with adrenaline.

Reproductive Health of Men with Spinal Cord Injury

Most men with spinal cord injury (SCI) are infertile due to a combination of erectile dysfunction, ejaculatory dysfunction, and abnormal semen quality. This article addresses issues that should be considered when managing the reproductive health of men with SCI. The authors present recommendations based on their decades of experience in managing the reproductive health of more than 1,000 men with SCI. Men with SCI face obstacles when pursuing sexual activity and/or biologic fatherhood. Hypogonadism and premature symptoms of aging may interfere with sexual function. Erectile dysfunction is prevalent in the SCI population, and treatments for erectile dysfunction in the general population are also effective in the SCI population. Most men with SCI cannot ejaculate with sexual intercourse. The procedures of penile vibratory stimulation (PVS) and/or electroejaculation (EEJ) are effective in obtaining an ejaculate from 97% of men with SCI. The ejaculate often contains sufficient total motile sperm to consider the assisted conception procedures of intrauterine insemination or even intravaginal insemination at home. If PVS and/or EEJ fail, sperm may be retrieved surgically from the testis or epididymis. Surgical sperm retrieval typically yields enough motile sperm only for in vitro fertilization with intracytoplasmic sperm injection. The majority of new cases of SCI occur in young men at the peak of their reproductive health. With proper medical management, these men can expect to experience active sexual lives and biologic fatherhood, if these are their goals. Numerous tools are available to physicians for helping these patients reach their goals.

Prevalence and Etiology of Hypogonadism in Young Men With Chronic Spinal Cord Injury: A Cross-Sectional Analysis From Two University-Based Rehabilitation Centers

BACKGROUND

Spinal cord injury (SCI) triggers an "accelerated aging" process that may include development of hypogonadism, even among younger men with SCI; however, few studies have investigated the prevalence or etiology of hypogonadism in men with SCI. Young men with SCI also are at increased risk for developing metabolic dysfunction after injury, which may be exacerbated by concomitant testosterone (T) deficiency, thus identifying the prevalence and risk factors for T deficiency in men with SCI is important for their long-term health.

OBJECTIVE

To investigate the prevalence, risk factors, and etiology of T deficiency (hypogonadism) in otherwise-healthy men with chronic, motor complete SCI.

DESIGN

Secondary cross-sectional analysis.

SETTING

Rehabilitation research centers in Washington, DC, and Miami, Florida.

PARTICIPANTS

Men (n = 58) aged 18-45 years with chronic (≥1 year), motor complete SCI without comorbidities or use of testosterone therapy.

METHODS

Plasma concentrations of hormones were measured with standardized assays. Body composition was assessed with dual-energy x-ray absorptiometry scan.

MAIN OUTCOME MEASUREMENTS

Serum total T and calculated free T.

RESULTS

T deficiency was more common in men after SCI than in a matched cohort of similarly-aged men without SCI (25%, SCI versus 6.7%, non-SCI, P < .001). The risk of hypogonadism appeared to be increased in men with more extensive injury and with higher percent body fat. The majority of men with SCI with low T had low serum LH levels, suggesting that central suppression of the hypothalamic-pituitary-gonadal axis may be the most common etiology of hypogonadism after SCI.

CONCLUSIONS

Hypogonadism is more common in young men with SCI than in similarly aged men without SCI, suggesting that SCI should be identified as a risk factor for T deficiency and that routine screening for hypogonadism should be performed in the SCI population.

LEVEL OF EVIDENCE

II.

Neuromuscular electrical stimulation and testosterone did not influence heterotopic ossification size after spinal cord injury: A case series

Neuromuscular electrical stimulation (NMES) and testosterone replacement therapy (TRT) are effective rehabilitation strategies to attenuate muscle atrophy and evoke hypertrophy in persons with spinal cord injury (SCI). However both interventions might increase heterotopic ossification (HO) size in SCI patients. We present the results of two men with chronic traumatic motor complete SCI who also had pre-existing HO and participated in a study investigating the effects of TRT or TRT plus NMES resistance training (RT) on body composition. The 49-year-old male, Subject A, has unilateral HO in his right thigh. The 31-year-old male, Subject B, has bilateral HO in both thighs. Both participants wore transdermal testosterone patches (4-6 mg/d) daily for 16 wk. Subject A also underwent progressive NMES-RT twice weekly for 16 wk. Magnetic resonance imaging scans were acquired prior to and post intervention. Cross-sectional areas (CSA) of the whole thigh and knee extensor skeletal muscles, femoral bone, and HO were measured. In Subject A (NMES-RT + TRT), the whole thigh skeletal muscle CSA increased by 10%, the knee extensor CSA increased by 17%, and the HO + femoral bone CSA did not change. In Subject B (TRT), the whole thigh skeletal muscle CSA increased by 13% in the right thigh and 6% in the left thigh. The knee extensor CSA increased by 7% in the right thigh and did not change in the left thigh. The femoral bone and HO CSAs in both thighs did not change. Both the TRT and NMES-RT + TRT protocols evoked muscle hypertrophy without stimulating the growth of pre-existing HO.

Low testosterone and non-alcoholic fatty liver disease: Evidence for their independent association in men with chronic spinal cord injury

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) has been claimed as a liver phenotype of metabolic syndrome, which in turn is associated with male hypogonadism. We assessed whether an independent association between NAFLD and androgen deficiency could be revealed in men with chronic spinal cord injury (SCI), who exhibit a high prevalence of biochemical androgen deficiency and a combination of risk factors for metabolic syndrome.

DESIGN

Fifty-five consecutive men with chronic SCI admitted to a rehabilitation program underwent clinical/biochemical evaluations and liver ultrasonography.

RESULTS

NAFLD was diagnosed in 27 patients (49.1%). Men with NAFLD were older and exhibited significantly higher body mass index, Homeostatic model assessment of insulin resistance, triglycerides and gamma-glutamyl transpeptidase values, lower total and free testosterone levels and they were engaged in a significantly poorer weekly leisure time physical activity (LTPA). At the multiple logistic regression analysis, only total and free testosterone levels exhibited a significant independent association with NAFLD. The risk of having NAFLD increased indeed of 1% for each decrement of 1 ng/dL of total testosterone and of 3% for each decrement of 1 pg/mL of free testosterone, after adjustment for confounders. In men with total testosterone < 300 ng/dL (36.4%) the prevalence of NAFLD reached 85%: they had a risk of having NAFLD significantly higher (∼12-fold) than those with total testosterone ≥ 300 ng/dL, after adjustment for confounders.

CONCLUSION

The evidence of an independent association between NAFLD and low testosterone is strongly reinforced by its demonstration in men with chronic SCI, in spite of the many confounders peculiar to this population.

Androgen receptor transcriptionally regulates μ-opioid receptor expression in rat trigeminal ganglia

The involvement of testosterone in pain, inflammation, and analgesia has been reported, but the role of androgen receptor (AR), a steroid receptor for testosterone, is not well understood. We have previously shown that peripheral inflammation upregulates μ-opioid receptor (MOR) in rat trigeminal ganglia (TG) in a testosterone-dependent manner. In this study, we hypothesized that testosterone regulates MOR expression via transcriptional activities of AR in TG. We first examined whether AR is co-expressed with MOR in TG neurons. Our immunohistochemical experiment revealed that AR staining is detected in neurons of all sizes in TG and that a subset of AR is expressed in MOR as well as in TRPV1-positive neurons. We identified the promoter region of the rat MOR gene contains putative AR binding sites. Using chromatin immunoprecipitation assay, we demonstrated that AR directly binds to these sites in TG extracts. We confirmed with luciferase reporter assay that AR activated the MOR promoter in response to androgens in a human neuroblastoma cell line (5H-5YSY). These data demonstrated that AR functions as a transcriptional regulator of the MOR gene activity. Finally, we showed that flutamide, a specific AR antagonist, prevents complete Freund's adjuvant (CFA)-induced upregulation of MOR mRNA in TG, and that flutamide dose-dependently blocks the efficacy of DAMGO, a specific MOR agonist, on CFA-induced mechanical hypersensitivity. Our results expand the knowledge regarding the role of androgens and their receptor in pain and analgesia and have important clinical implications, particularly for inflammatory pain patients with low or compromised plasma testosterone levels.

Association between 25(OH)-vitamin D and testosterone levels: Evidence from men with chronic spinal cord injury

OBJECTIVE

As an independent linear association between 25-hydroxyvitamin D (25(OH)D) and testosterone levels is controversial, this study aimed to explore this topic in men with chronic spinal cord injury (SCI), who exhibit a high prevalence of both androgen and vitamin D deficiency.

DESIGN

Forty-nine men with chronic SCI consecutively admitted to a rehabilitation program underwent clinical/biochemical evaluations.

RESULTS

Deficiency of 25(OH)D (<20 ng/mL) was found in 36 patients (73.5%). They exhibited significantly lower total testosterone and free testosterone levels, higher parathyroid hormone (PTH) and HOMA-IR, a poorer functional independence degree, and were engaged in poorer weekly leisure time physical activity (LTPA). Significant correlates of 25(OH)D levels were: total testosterone, free testosterone, PTH, functional independence degree and weekly LTPA. At the linear regression models, lower 25(OH)D levels were associated with both lower total and free testosterone after adjustment for age, smoking, alcohol consumption, comorbidities and HOMA-IR. However, after full adjustment, also including functional independence degree, BMI and LTPA, only the association of lower 25(OH)D with lower free testosterone was still significant.

CONCLUSION

In men with SCI, 25(OH)D correlates with total and free testosterone and exhibits an independent linear association with free testosterone. Regardless of this independent link, hypovitaminosis D and androgen deficiency are markers of poor health, sharing common risk factors to take into account in the rehabilitative approach to patients with SCI.

The Effects of Testosterone on Oxidative Stress Markers in Mice with Spinal Cord Injuries

Background

Spinal cord injury (SCI) causes infertility in male patients through erectile dysfunction, ejaculatory dysfunction, semen and hormone abnormalities. Oxidative stress (OS) is involved in poor semen quality and subsequent infertility in males with SCI. The aim of this study is to examine the effects of SCI on the level of testosterone hormone.

Materials and Methods

In this experimental study, we evaluated the effects of exogenous testosterone on the activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) as well as the levels of malondialdehyde (MDA) and protein carbonylation (PCO), as markers of OS, in 10 groups of SCI mice. Total antioxidant capacity (TAC) was determined using the 2,29-azinobis-(3-ethylbenzothiazoline- 6-sulfonic acid) (ABTS) radical cation assay.

Results

Exogenous testosterone administration in mice with SCI significantly reduced SOD and GPx enzyme activities and MDA level. There was no significant decrease in PCO content. In addition, TAC remarkably increased in the sham and SCI groups not treated with testosterone but remained unchanged in all other experimental groups. Exogenous testosterone also reduced serum testosterone levels in all groups except the positive control group.

Conclusion

Our cumulative data indicated that SCI could cause sterility by disturbing the plasmatic testosterone balance. The normal level of endogenous testosterone was not completely restored by exogenous testosterone administration.

Intermittent hypoxia and neurorehabilitation

In recent years, it has become clear that brief, repeated presentations of hypoxia [i.e., acute intermittent hypoxia (AIH)] can boost the efficacy of more traditional therapeutic strategies in certain cases of neurologic dysfunction. This hypothesis derives from a series of studies in animal models and human subjects performed over the past 35 yr. In 1980, Millhorn et al. (Millhorn DE, Eldridge FL, Waldrop TG. Respir Physiol 41: 87-103, 1980) showed that electrical stimulation of carotid chemoafferent neurons produced a persistent, serotonin-dependent increase in phrenic motor output that outlasts the stimulus for more than 90 min (i.e., a "respiratory memory"). AIH elicits similar phrenic "long-term facilitation" (LTF) by a mechanism that requires cervical spinal serotonin receptor activation and de novo protein synthesis. From 2003 to present, a series of studies demonstrated that AIH can induce neuroplasticity in the injured spinal cord, causing functional recovery of breathing capacity after cervical spinal injury. Subsequently, it was demonstrated that repeated AIH (rAIH) can induce recovery of limb function, and the functional benefits of rAIH are greatest when paired with task-specific training. Since uncontrolled and/or prolonged intermittent hypoxia can elicit pathophysiology, a challenge of intermittent hypoxia research is to ensure that therapeutic protocols are well below the threshold for pathogenesis. This is possible since many low dose rAIH protocols have induced functional benefits without evidence of pathology. We propose that carefully controlled rAIH is a safe and noninvasive modality that can be paired with other neurorehabilitative strategies including traditional activity-based physical therapy or cell-based therapies such as intraspinal transplantation of neural progenitors.

Bone mass and hormone analysis in patients with spinal cord injury: evidence for a gonadal axis disruption

CONTEXT

Bone loss is a constant finding in patients with spinal cord injury (SCI).

OBJECTIVE

We sought to evaluate potential modifiable factors that could lead to bone loss in complete motor paraplegia by examining gonadal axis hormones, vitamin D status, and bone markers.

DESIGN

This is a cross sectional.

SETTING

It includes SCI Outpatient.

PATIENTS AND OTHER PARTICIPANTS

Twenty-nine chronic male patients with SCI were compared with 17 age-matched, able-bodied men.

MAIN OUTCOME MEASURE

The bone mineral density (BMD) of lower limbs and lumbar spine were measured using dual x-ray absorptiometry. Parathormone, 25-hydroxyvitamin D [25(OH)D], collagen type I C-terminal telopeptide (CTX), and sexual hormone were measured.

RESULTS

Patients with SCI had lower BMD at the inferior limbs sites. CTX showed an inverse relationship with the time since injury. Patients had lower free T levels (SCI, 12.00 ± 2.91 vs controls, 19.51 ± 5.72; P ≤ .001), and the majority (72%) had normal/low levels of gonadotropins. Low T, however, was not related to low bone mass in patients with SCI. In the controls, the 25(OH)D level was positively correlated with the T and with the lumbar spine BMD, but these correlations were not observed in the SCI.

CONCLUSIONS

Impairment of testicular function after SCI was indicated by the low levels of T and the loss of correlation between T and 25(OH)D levels; this correlation was present in the able-bodied controls. Inappropriate levels of gonadotropins were identified in most patients, featuring a hypogonadotropic hypogonadism and suggesting a disruption of the pituitary-gonadal axis. T concentrations might not be an effective target for bone loss therapy.