Immunoreactive and bioactive luteinizing hormone in pubertal patients with chronic renal failure. Cooperative Study Group on Pubertal Development in Chronic Renal Failure

Pubertal luteinizing hormone levels in children with chronic kidney disease and association with change in glomerular filtration rate

BACKGROUND

Children with chronic kidney disease (CKD) are at risk for abnormalities in pubertal development. We aimed to describe the timing of pubertal onset by luteinizing hormone (LH) levels and the association between hormonal onset of puberty with changes in GFR.

METHODS

Data from the Chronic Kidney Disease in Children (CKiD) study were collected prospectively. GFR was estimated at annual visits and measured by iohexol clearance every other year. LH was measured from stored repository serum samples in a nested sample of 124 participants. Hormonal onset of puberty was defined as LH level greater than or equal to 0.3 IU/L. A mixed effects model with random intercepts and slopes was used to compare the slope of decline of GFR before and after hormonal onset of puberty. The model was adjusted for age, glomerular disease diagnosis, baseline proteinuria on the log scale, and BMI.

RESULTS

Median age at hormonal onset of puberty was 9.9 years (IQR 8.1, 11.9) in girls and 10.2 years (IQR 9.2, 11.0) in boys. The mixed effects model showed faster decline in both estimated GFR and measured GFR in boys after hormonal onset of puberty (p < 0.001), and a similar but attenuated accelerated estimated GFR decline was observed for girls with no difference for measured GFR.

CONCLUSIONS

LH levels in the post-pubertal range were observed prior to clinical manifestations of puberty in children with CKD. Hormonal onset of puberty was associated with faster decline in GFR, particularly among boys with CKD.

Serum prolactin and gonadal hormones in hemodialysis women: a meta-analysis

BACKGROUND

A meta-analysis followed by PRISMA 2020 statement was performed aiming to present a whole prolactin and sex hormone profile in hemodialysis women.

METHODS

Literatures were searched in PubMed, Cochrane library, Embase, and Web of science before March 11, 2023. Trial sequential analysis (TSA) was performed to test the conclusiveness of this meta-analysis. Egger's test and trim-and-fill analysis was used to test publication bias. We took standardized mean difference (SMD) as pool effect of hormones values including prolactin (PRL), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and progesterone (P). This study was registered in PROSPERO and the number was CRD42023394503.

RESULTS

Twenty-two articles from 13 countries were analyzed. Combining the results of TSA and meta-analysis, we found that compared with healthy control, hemodialysis women had higher PRL, follicular FSH and LH values and lower P levels (PRL: I2 = 87%, SMD 1.24, 95% CI: 0.79-1.69, p < 0.00001; FSH: I2 = 0%, SMD 0.34, 95% CI: 0.13-0.55, p = 0.002; LH: I2 = 39%, SMD 0.64, 95% CI: 0.34-0.93, p < 0.00001; P: I2 = 30%, SMD - 1.62, 95% CI: -2.04 to -1.20, p < 0.00001). What's more, compared with women after renal transplantation, hemodialysis women had higher PRL levels (I2 = 0%, SMD 0.51, 95% CI: 0.25-0.78, p = 0.0001). There was not enough evidence to draw a conclusion on the comparison of hormones between regular and irregular menses hemodialysis women. Egger's test and trim-and-fill analysis didn't show significant publication bias.

CONCLUSIONS

Hemodialysis women had higher serum PRL, follicular phase FSH, LH and lower serum P values compared with healthy control. PRL values of hemodialysis women were also higher than that of women after renal transplantation.

Insights from the 4C-T Study suggest increased cardiovascular burden in girls with end stage kidney disease before and after kidney transplantation

Mortality in children with kidney failure is higher in girls than boys with cardiovascular complications representing the most common causes of death. Pulse wave velocity (PWV), a measure of vascular stiffness, predicts cardiovascular mortality in adults. Here, PWV in children with kidney failure undergoing kidney replacement therapy was investigated to determine sex differences and potential contributing factors. Two-hundred-thirty-five children (80 girls; 34%) undergoing transplantation (150 pre-emptive, 85 with prior dialysis) having at least one PWV measurement pre- and/or post-transplantation from a prospective cohort were analyzed. Longitudinal analyses (median/maximum follow-up time of 6/9 years) were performed for PWV z-scores (PWVz) using linear mixed regression models and further stratified by the categories of time: pre-kidney replacement therapy and post-transplantation. PWVz significantly increased by 0.094 per year and was significantly higher in girls (PWVz +0.295) compared to boys, independent of the underlying kidney disease. During pre-kidney replacement therapy, an average estimated GFR decline of 4ml/min/1.73m² per year was associated with a PWVz increase of 0.16 in girls only. Higher diastolic blood pressure and low density lipoprotein were independently associated with higher PWVz during pre-kidney replacement therapy in both sexes. In girls post-transplantation, an estimated GFR decline of 4ml/min/1.73m² per year pre-kidney replacement therapy and a longer time (over 12 months) to transplantation were significantly associated with higher PWVz of 0.22 and of 0.57, respectively. PWVz increased further after transplantation and was positively associated with time on dialysis and diastolic blood pressure in both sexes. Thus, our findings demonstrate that girls with advanced chronic kidney disease are more susceptible to develop vascular stiffening compared to boys, this difference persist after transplantation and might contribute to higher mortality rates seen in girls with kidney failure.

Elevated circulating luteinizing hormone levels are associated with diabetic macroalbuminuria in Chinese men and postmenopausal women: A cross-sectional study

BACKGROUND

Associations between sex hormones and diabetic vascular complications have recently been studied, but the role luteinizing hormone (LH) plays in diabetic kidney disease (DKD) remains uncertain. We aimed to investigate the relationship of LH and DKD in Chinese men and postmenopausal women with type 2 diabetes mellitus (T2DM).

METHODS

Data were collected from 1775 T2DM men and postmenopausal women in hospital. The odds ratios (OR) and corresponding 95% confidence intervals (CI) in relation to LH quartiles were obtained by multiple logistic regression analysis.

RESULTS

LH levels were significantly higher in patients with macroalbuminuria than in those with microalbuminuria, but were not higher in patients with microalbuminuria than in those with normoalbuminuria. Consistently, LH in those with an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73m² were significantly higher than in those with eGFR≥60 mL/min/1.73m² . The prevalence of macroalbuminuria was obviously increased for subjects of the fourth quartile of LH vs the first to third quartile (20.4% vs 6.2%, 8.0%, 12.2% in men; 25.3% vs 5.5%, 3.8%, 9.3% in postmenopausal women). Multivariate logistic regression demonstrated that subjects within the highest quartile of LH had higher odds of macroalbuminuria than those within the lowest quartile (OR 4.00, 95% CI, 1.87-8.55 for men; OR 9.62, 95% CI, 3.42-27.08 for postmenopausal women), independent of age, diabetes duration, or other metabolic factors. The area under the curve for detecting macroalbuminuria based on LH was 0.662 for men, and 0.767 for postmenopausal women.

CONCLUSION

High LH levels are positively associated with established DKD among Chinese men and postmenopausal women. Elevated LH may be a promising clinical factor for identifying established DKD.

Near-adult height in male kidney transplant recipients started on growth hormone treatment in late puberty

BACKGROUND

Growth retardation and its impact on adult height is considered to be one of the most common complications in patients with chronic kidney disease (CKD). Treatment with recombinant human growth hormone (rhGH) has been effective in improving growth in kidney transplantation (KTx) patients, but little data are available on adult height in patients who began rhGh treatment in late puberty.

METHODS

Near-adult height was evaluated in 13 KTx patients treated with rhGH [growth hormone group (GHGr); dose 9.33 mg/m² per week] for a period of at least 18 months. At initiation of rhGH treatment, testicular volume was >8 ml and serum testosterone was >1 ng/ml compared with the control group (CGr) of ten KTx patients who did not receive rHGH. All subjects were of similar chronological age and bone age and had similar creatinine clearance (CrCl) levels, cumulative corticoid dose, height standard deviation score (SDS), target height SDS, and target height:initial height at the beginning of the study.

RESULTS

Near-adult height was significantly greater in the GHGr than in the CGr (-1.8 ± 0.8 vs. -2.9 ± 1.1; p = 0.018). The difference between initial height and near-adult height in the GHGr revealed a significant height gain (initial height -3.1 ± 1.1; near-adult height -1.8 ± 0.8 SDS, respectively; delta 1.2 ± 0.3; p = 0.021). The CrCl level was not significantly different between the GHGr and CGr at either at study initiation or when attaining near-adult height (p = 0.74 and p = 0.23, respectively).

CONCLUSIONS

Treatment with rhGH was effective in improving adult height in KTx patients who began treatment in late puberty, without any effect on renal function.

Pubertal development in children with chronic kidney disease

Impairment of pubertal growth and sexual maturation resulting in reduced adult height is an significant complication in children suffering from chronic kidney disease (CKD). Delayed puberty and reduced pubertal growth are most pronounced in children with pre-existing severe stunting before puberty, requiring long-term dialysis treatment, and in transplanted children with poor graft function and high glucocorticoid exposure. In pre-dialysis patients, therapeutic measures to improve pubertal growth are limited and mainly based on the preservation of renal function and the use of growth hormone treatment. In patients with end-stage CKD, early kidney transplantation with steroid withdrawal within 6 months of renal transplantation allows for normal pubertal development in the majority of patients. This review focuses on the underlying pathophysiology and strategies for improving height and development in these patients.

Gonadal dysfunction in chronic kidney disease

Sexual dysfunction is a common finding in both men and women with chronic kidney failure. Common disturbances include erectile dysfunction in men, menstrual abnormalities in women, and decreased libido and fertility in both sexes. These abnormalities are primarily organic in nature and are related to uremia as well as the other comorbid conditions that frequently occur in the chronic kidney failure patient. Fatigue and psycho social factors related to the presence of a chronic disease are also contributory factors. Disturbances in the hypothalamic-pituitary-gonadal axis can be detected prior to the need for dialysis but continue to worsen once dialytic therapy is initiated. Impaired gonadal function is prominent in uremic men while the disturbances in the hypothalamic-pituitary axis are more subtle. By contrast, central disturbances are more prominent in uremic women. Therapy is initially directed towards optimizing the delivery of dialysis, correcting anemia with recombinant erythropoietin, and controlling the degree of secondary hyperparathyroidism with vitamin D. For many practicing nephrologists sildenafil has become the first line therapy in the treatment of impotence. In the hypogonadal man whose only complaint is decreased libido, testosterone may be of benefit. Regular gynecologic follow up is required in uremic women to guard against potential complications of unopposed estrogen effect. Uremic women should be advised against pregnancy while on dialysis. Successful transplantation is the most effective means of restoring normal sexual function in both men and women with chronic kidney failure.

Prevalence of subnormal testosterone concentrations in men with type 2 diabetes and chronic kidney disease

BACKGROUND

One-third of men with type 2 diabetes have subnormal testosterone concentrations along with inappropriately normal LH and FSH concentrations. It is not known if the presence of renal insufficiency affects free testosterone concentrations in men with type 2 diabetes.

HYPOTHESIS

We hypothesized that type 2 diabetic men with chronic renal disease (CKD; estimated glomerular filtration rate (eGFR) < 60 ml/min per 1.73 m(2)) have lower free testosterone concentrations than men with normal renal function (eGFR ≥ 60 ml/min per 1.73 m(2)).

STUDY DESIGN AND SETTING

This is a retrospective chart review of patients attending diabetes and nephrology clinics. Men with type 2 diabetes who had the following information available were included in the study: testosterone (total and free) done by LC/MS-MS followed by equilibrium dialysis, sex hormone binding globulin, LH, FSH and prolactin concentrations.

PARTICIPANTS

We present data on T and gonadotropin concentrations in 111 men with type 2 diabetes and CKD (stages 3-5) and 182 type 2 diabetic men without CKD.

RESULTS

The prevalence of subnormal free testosterone concentrations was higher in men with type 2 diabetes and CKD as compared to those without CKD (66% vs 37%, P < 0.001). Men with CKD had a higher prevalence of hypergonadotropic hypogonadism (26% vs 5%, P < 0.001) but not of hypogonadotropic hypogonadism (HH; 40% vs 32%, P = 0.22). There was an increase in the prevalence of hypergonadotropic hypogonadism with decreasing eGFR. Fifty-two percent of men with renal failure (CKD stage 5) had hypergonadotropic hypogonadism and 25% had HH. In men with CKD, the hemoglobin concentrations were lower in those with subnormal free T concentrations as compared to men with normal free T concentrations (119 ± 19 vs 128 ± 19 g/l, P = 0.04).

CONCLUSIONS

Two-thirds of men with type 2 diabetes and CKD have subnormal free T concentrations. The hypogonadism associated with CKD is predominantly hypergonadotropic.

Sexual and gonadal dysfunction in chronic kidney disease: Pathophysiology

Sexual and gonadal dysfunction/infertility are quite common in patients with chronic kidney disease. Forty percent of male and 55% of female dialysis patients do not achieve orgasm. The pathophysiology of gonadal dysfunction is multifactorial. It is usually a combination of psychological, physiological, and other comorbid factors. Erectile dysfunction in males is mainly due to arterial factors, venous leakage, psychological factors, neurogenic factors, endocrine factors, and drugs. Sexual dysfunction in females is mainly due to hormonal factors and manifests mainly as menstrual irregularities, amenorrhea, lack of vaginal lubrication, and failure to conceive. Treatment of gonadal dysfunction in chronic kidney disease is multipronged and an exact understanding of underlying pathology is essential in proper management of these patients.

Growth in chronic kidney disease

Poor growth is a common sequela of CKD in childhood. It not only affects the psychosocial development of a child but also has significant effects even in the adult life. The multifactorial etiology and severe consequences of growth failure in CKD warrant evaluation of all the modifiable and nonmodifiable causes. Treatment strategies must be directed toward the specific factors for each child with CKD. Among the various metabolic, nutritional, and hormonal disturbances complicating CKD, disordered growth hormone (GH) and insulin-like growth factor-1 axis are important contributors toward poor growth in children with CKD. CKD is recognized as a state of GH resistance rather than GH deficiency, with multiple mechanisms contributing to this GH resistance. Recombinant GH (rGH) therapy can be used in this population to accelerate growth velocity. Although its use has been shown to be effective and safe in children with CKD, there continues to be some uncertainty and reluctance among practitioners and families regarding its usage, thereby resulting in a surprisingly low use in children with CKD. This review focuses on the pathogenesis of growth failure, its effect, and management strategies in children with CKD.

Growth after renal transplantation

Growth may be severely impaired in children with chronic renal insufficiency. Since short stature can have major consequences on quality of life and self-esteem, achieving a 'normal' height is a crucial issue for renal transplant recipients. However, despite successful renal transplantation, the final height attained by most recipients is not the calculated target height. Catch-up growth spurts post-transplantation are usually insufficient to compensate for the retardation in growth that has occurred during the pre-transplant period. Longitudinal growth post-transplantation is therefore influenced by the age at transplantation but also by subsequent allograft function and steroid exposure, both of which interfere with the growth hormone/insulin-like growth factor axis. The management of growth retardation in renal transplant recipients includes adequate nutritional intake, correction of metabolic acidosis, prevention of bone disease, steroid-sparing strategies and a supraphysiological dose of recombinant human growth hormone in selected cases.

Analyses of age, gender and other risk factors of erythropoietin resistance in pediatric and adult dialysis cohorts

Previous studies often report lower responses to erythropoietin (EPO) therapy in pediatric patients on chronic dialysis than those of adults. Because of the greater capacity for hematopoiesis in the younger population, these studies may be confounded by poorly identified variables. Thus, we made parallel studies of pediatric and adult cohorts to explore the relationship between age, gender and other risk factors with EPO resistance. Thirty pediatric subjects (aged 8-20 years) and 66 adult subjects (aged 22-85 years) on chronic hemodialysis and EPO were enrolled. After stratification by 50th percentile of EPO response, the best predictive model was identified by backward elimination of the risk factors with the least contribution to the regression. Relationship between age, gender and EPO resistance was examined by analysis of covariance (ANCOVA). The most predictive model of EPO response for the pediatric cohort had, as the major variables, urea clearance x dialysis duration/total body water (Kt/V), urea reduction ratio (URR), intact parathyroid hormone (iPTH), blood loss, normalized protein catabolic rates (nPCR) and indices of malnutrition and inflammation, whereas adults had iron and folate deficiencies as the dominant variables. Although EPO resistance was more common in female subjects than in male subjects, relationship with neither age nor gender was significant. Furthermore, the prescription of a larger (initiating) EPO dose by pediatric physicians compared with adult nephrologists confounded the interaction between age and EPO resistance. In summary EPO resistance in the pediatric dialysis cohort was predicted by nutritional deficits, inflammation, poor dialysis, and hyperparathyroidism, while iron and folate deficits were the major determinants in adults. Although confounded by the pattern of EPO prescription, neither age nor gender was predictive of EPO resistance in the two study groups.

[Growth hormone therapy for children with chronic diseases]

Growth disorders are commonly observed in children suffering from chronic diseases. The pathogenesis of growth failure is multifactorial. In chronic inflammatory diseases such as juvenile idiopathic arthritis and inflammatory bowel disease, growth is also affected by pro-inflammatory cytokines. Patients with chronic diseases might also become growth hormone (GH) deficient. However, normal or increased GH secretion with reduced plasma concentrations of insulin-like growth factor-I indicate a degree of GH insensitivity in some patients. Growth damage can increase with specific treatments, especially if glucocorticoids are used. GH therapy has been used to reduce the consequences of the disease and long-term steroid therapy in these patients. In this review, it is reported the encouraging results of GH treatment in growth-retarded children with chronic diseases, both in well defined indications as well in situations still under investigation.

Applying the Growth Failure in CKD Consensus Conference: evaluation and treatment algorithm in children with chronic kidney disease

Growth failure is a common and significant clinical problem for children with chronic kidney disease (CKD), particularly those with chronic renal insufficiency (CRI). Children with CRI (typically defined by a glomerular filtration rate [GFR] <75 mL/min/1.73 m2) who have growth impairment exhibit a variety of medical and psychological problems in addition to increased mortality. Growth failure in children with CKD is usually multifactorial in etiology, including abnormalities in the growth hormone (GH)-insulin-like growth factor (IGF)-I axis and a variety of nutritional and metabolic concerns characteristic of CKD. Proper management of these factors contributes to better growth in affected children. Although the safety and efficacy of recombinant human GH (rhGH) therapy in promoting growth in children with CKD are well established, recent data indicate that the use of rhGH administration in children with CKD and growth failure remains low. Recently, guidelines were developed by the Consensus Conference for Evaluation and Treatment of Growth Failure in Children with CKD. This paper focuses on the application of these guidelines to children with CKD.

Assessment and treatment of short stature in pediatric patients with chronic kidney disease: a consensus statement

Growth failure is a clinically important issue in children with chronic kidney disease (CKD) and is associated with significant morbidity and mortality. Many factors contribute to impaired growth in these children, including abnormalities in the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis, malnutrition, acidosis, and renal bone disease. The management of growth failure in children with CKD is complicated by the presence of other disease-related complications requiring medical intervention. Despite evidence of GH efficacy and safety in this population, some practitioners and families have been reluctant to institute GH therapy, citing an unwillingness to comply with daily injections, reimbursement difficulties, or impending renal transplantation. Suboptimal attention to growth failure management may be further compounded by a lack of clinical guidelines for the appropriate assessment and treatment of growth failure in these children. This review of growth failure in children with CKD concludes with an algorithm developed by members of the consensus committee, outlining their recommendations for appropriate steps to improve growth and overall health outcomes in children with CKD.

Puberty and chronic kidney disease

Puberty is a period of dramatic physiologic changes when children become adults. Chronic kidney disease (CKD), like many disorders, may delay or blunt the onset and outcomes of puberty. These include attainment of adult height and reproductive capacity. Although nutrition and treatment effects may contribute to these phenomena, increasing evidence supports direct biological effects of CKD on the neurohypophyseal axis that controls these systems. Although CKD affects puberty, this life period also impacts the progression of CKD. Diabetes mellitus, posterior urethral valves, reflux nephropathy, and hypoplasia all appear to accelerate with sexual maturation. Potential mechanisms include increases in blood pressure and body size as well as altered endocrine physiology. Better understanding of the interactions of puberty and CKD may lead to better outcomes for children with CKD as well as longer preservation of native kidney function.

Outcomes associated with hypogonadism in men with chronic kidney disease

Chronic kidney disease is commonly accompanied by disturbances in the hypothalamic-pituitary-gonadal axis. Such disturbances in men give rise to hypogonadism and low circulating testosterone levels. The deficiency in testosterone can contribute to clinical outcomes such as sexual dysfunction, decreased bone mineralization, malnutrition and decreased muscle mass, and anemia. The administration of androgens to nonuremic hypogonadal men is usually effective in treating such outcomes. By contrast, the response to therapy in uremic men tends to be much less predictable. This variability in response is not surprising, because these same clinical outcomes can be the result of other aspects of the uremic state or the comorbid conditions that are frequently present in men with chronic kidney disease. Although further studies are needed, testosterone therapy may prove most useful as an adjunct to other more general therapies designed to address the uremic state.

Hypothalamic release of nitric oxide and interaction with amino acid neurotransmitters in chronically uraemic rats

BACKGROUND

The activity of the hypothalamic gonadotrophin-releasing hormone (GnRH) pulse generator is diminished in uraemia. Since GnRH release is influenced by nitric oxide (NO) neurotransmission, we examined the integrity of hypothalamic NO neurotransmission in the chronically uraemic rat model.

METHODS

Adult male castrated rats were rendered uraemic by two-stage 5/6 nephrectomy. Basal, N-methyl-D-aspartate (NMDA)-stimulated and DL-2-amino-5-phosphonovaleric acid (AP-5)-inhibited NO outflow was measured in uraemic and sham-nephrectomized control animals via a microdialysis probe in the medial preoptic area (MPOA). The influence of the noradrenergic system was evaluated by blocking noradrenergic neurons with N-(2-chloroethyl)-N-ethyl 2-bromobenzylamine (DSP-4). The activity of different NO synthase (NOS) isoforms was investigated by administration of the isoform-specific NOS inhibitors S-methyl-L-thiocitrulline (SMLT) and L-N6-(1-iminoethyl)-lysine (L-NIL). Moreover, hypothalamic mRNA expression of the individual NOS isoforms was quantitated by real-time reverse transcriptase-polymerase chain reaction. Effects of NO on amino acid outflow were assessed by addition of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP).

RESULTS

The expression of different NOS species and basal NO outflow did not differ between uraemic and control animals. Administration of the NO donor SNAP increased local NO production and amino acid outflow similarly in both groups. SMLT but not L-NIL, an inhibitor of the inducible NOS isoform, reduced NO outflow in both groups. AP-5 equally decreased, and noradrenergic blockade increased NMDA-stimulated NO outflow in both groups.

CONCLUSIONS

NO is produced locally and may interfere with amino acid neurotransmission in the rat MPOA. Uraemia did not interfere with NO neurotransmission in our study.

Impaired Autofeedback Regulation of Hypothalamic Norepinephrine Release in Experimental Uremia

Chronic renal failure (CRF) is associated with multiple hypothalamic dysfunctions, including reduced secretion of gonadotropin-releasing hormone (GnRH). Because GnRH release is tightly controlled by sympathetic neuronal input, a possible alteration of local noradrenergic neurotransmission in experimental CRF was evaluated. Basal, stimulated, and autoinhibited norepinephrine (NE) release was assessed in hypothalamic and hippocampal tissue slices obtained from 5/6-nephrectomized and control rats. Autoinhibition-free NE release from brain slices, prelabeled with [3H]NE and superfused with physiologic buffer, was stimulated by six electrical pulses, 100 Hz (pseudo-one-pulse stimulation). Autoinhibited NE release was induced by 90 pulses at 3 Hz. The release of tritiated NE was measured upon addition of increasing concentrations of unlabeled NE to exogenously activate the inhibitory alpha2-autoreceptor. Although neither basal nor stimulated NE release differed between the groups, significantly lower pIC50 and Imax estimates of the concentration-response curves of exogenous NE on [3H]NE release were observed in CRF rats, suggesting a diminished autoinhibition of hypothalamic noradrenergic terminals in CRF. Western blotting of tissue homogenates disclosed a significantly reduced abundance of alpha2-autoreceptor protein in hypothalamic tissue from CRF rats. These abnormalities were selectively observed in the hypothalamus, whereas noradrenergic autoinhibition seemed unaltered in the hippocampus. The results suggest a diminished autoinhibition of hypothalamic NE release in CRF. Although impaired hypothalamic NE autoinhibition does not explain reduced GnRH secretion in CRF, it may be involved in the pathogenesis of sympathetic hyperactivity associated with this condition.

Gonadal dysfunction in systemic diseases

Gonadal function is significantly affected in many acute and chronic systemic diseases. As the function of the testes and the ovaries is determined by the integrity of the hypothalamic-pituitary-gonadal axis, it is obvious that a systemic disease may affect one or more levels of the axis in such a manner that the gonadal dysfunction may have various clinical and laboratory manifestations. In this brief review, the most common disturbances seen in the main systemic diseases will be discussed.

Neuroendocrine adaptations in renal disease

Chronic renal failure (CRF) disrupts the time-dependent secretion of multiple hormones. The present review focuses on altered pulsatile release of peptide hormones. CRF is marked by impaired tissue actions, disorderly release patterns, and relative [growth hormone (GH)] or absolute [luteinizing hormone (LH)] deficiency of secretion. At the hypothalamo-pituitary level, experimental evidence suggests that CRF reduces the synthesis and/or release of the cognate hypothalamic releasing factors, GHRH and LHRH, and enforces excessive inhibition by somatostatin. Parathyroid hormone (PTH) and insulin are secreted in both basal and pulsatile modes, wherein the latter is putatively coordinated by autonomic innervation. Amplitude and frequency-dependent adaptations of PTH and insulin outflow fail in CRF, as assessed under steady-state conditions and during metabolic drive (i.e., calcium for PTH and glucose for insulin). A common feature in CRF is a diminished mass of hormone released per burst, due in principle to attenuation of feedforward signals and/or accentuation of (unknown) feedback signals. Damping of neuronal control and/or prolonged network response times may contribute to aberrant pulse frequency, disproportionate basal (nonpulsatile) hormone release, and consistent erosion of secretory process regularity in the uremic state. The homeostatic consequences of distorted secretory dynamics, tissue resistance, impaired hormone clearance, and altered mean agonist concentrations are evident in certain therapeutic interventions, such as GH supplementation in CRF.

Sexual dysfunction in men and women with chronic kidney disease and end-stage kidney disease

Sexual dysfunction is a common finding in both men and women with chronic kidney failure. Common disturbances include erectile dysfunction in men, menstrual abnormalities in women, and decreased libido and fertility in both sexes. These abnormalities are primarily organic in nature and are related to uremia as well as the other comorbid conditions that frequently occur in the chronic kidney failure patient. Fatigue and psychosocial factors related to the presence of a chronic disease are also contributory factors. Disturbances in the hypothalamic-pituitary-gonadal axis can be detected before the need for dialysis but continue to worsen once dialytic therapy is initiated. Impaired gonadal function is prominent in uremic men, whereas the disturbances in the hypothalamic-pituitary axis are more subtle. By contrast, central disturbances are more prominent in uremic women. Therapy is initially directed toward optimizing the delivery of dialysis, correcting anemia with recombinant erythropoietin, and controlling the degree of secondary hyperparathyroidism with vitamin D. For many practicing nephrologists, sildenafil has become the first line therapy in the treatment of impotence. In the hypogonadal man whose only complaint is decreased libido, testosterone may be of benefit. Regular gynecologic follow-up is required in uremic women to guard against potential complications of unopposed estrogen effect. Uremic women should be advised against pregnancy while on dialysis. Successful transplantation is the most effective means of restoring normal sexual function in both men and women with chronic kidney failure.

Circulating inhibitor of gonadotropin releasing hormone secretion by hypothalamic neurons in uremia

BACKGROUND

Previous studies have suggested a neuroendocrine defect underlying uremic hypogonadism, characterized by a reduced secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH).

METHODS

We studied the GnRH-producing GT1-7 cell line and the LH-producing LbetaT-2 pituitary cell line under uremic conditions to investigate whether substances circulating in uremic plasma directly affect hypothalamic or pituitary hormone secretion. The cells were incubated with serum from 5/6-nephrectomized or sham-nephrectomized castrated rats, respectively. Furthermore, GT1 cells were incubated with delipidated sera, serum subfractions separated by molecular weight, or several peptide hormones. Cellular viability, apoptosis rate and extracellular hormone degradation were assessed separately. GnRH and LH were measured by RIA in supernatants and cell lysates. GnRH gene expression was assessed by Northern blot.

RESULTS

Uremic serum caused a reduction of extracellular GnRH concentration by 31%, whereas intracellular GnRH increased by 12%. This effect was independent of serum lipids and enzymatic GnRH degradation but was abolished by trypsin digestion. Cellular viability, apoptosis rates and GnRH gene expression did not differ between the two groups. The inhibitory activity was recovered from the high-molecular weight fraction, whereas the fraction <5 kD had stimulatory activity. In contrast, uremic serum did not affect LH secretion from LbetaT-2 cells, indicating that the hypoactivity of the hypothalamo-pituitary gonadotrope unit results from an inhibition at the hypothalamic rather than the pituitary level.

CONCLUSIONS

Our results suggest that uremic serum contains macromolecular and hydrophilic peptide(s) able to specifically suppress the neurosecretion of GnRH from GT1-7 cells.

Experimental Uremia Affects Hypothalamic Amino Acid Neurotransmitter Milieu

Abstract. Chronic renal failure is associated with delayed puberty and hypogonadism. To investigate the mechanisms subserving the reported reduced pulsatile release of gonadotropin-releasing hormone (GnRH) in chronic renal failure, this study examined the amino acid neurotransmitter milieu in the medial preoptic area (MPOA), the hypothalamic region where the GnRH-secreting neurons reside, in 5/6-nephrectomized male rats and in ad libitum-fed or pair-fed controls. All rats were castrated and received either a testosterone or a vehicle implant to evaluate additional effects of the prevailing sex steroid milieu. Local excitatory (essential amino acids: aspartate, glutamate) and inhibitory (γ-aminobutyric acid [GABA], taurine) amino acid transmitter outflow in the MPOA was measured by microdialysis via stereotactically implanted cannulae in the awake, freely moving rats. In addition to basal extracellular concentrations, the neurosecretory capacity was assessed by the addition of 100 mM KCl to the dialysis fluid. The mechanisms of neurosecretion were evaluated further by inhibition of vesicular release with the use of Ca2+-free, Mg2+-enriched dialysis fluid and by local perfusion with inhibitors of voltage-dependent synaptic release (1 μM tetrodotoxin) and of GABA reuptake (0.5 mM nipecotic acid). In the uremic rats, basal outflow of GABA, glutamate and aspartate, and K+-stimulated aspartate outflow were increased. K+-stimulated GABA and glutamate release was less sensitive to Ca2+ depletion in the uremic than in the control rats. The elevated basal GABA and essential amino acid outflow in the uremic rats was due to a voltage- and Ca2+-independent mechanism. GABA reuptake was inhibited proportionately by nipecotic acid in uremic and pair-fed control rats. Testosterone supplementation had no independent effects on neurotransmitter outflow. In summary, the amino acid neurotransmitter milieu is altered in the MPOA of uremic rats by a nonsynaptic, nonvesicular mechanism. These abnormalities may contribute to the impaired function of the GnRH pulse generator.

Puberty in chronic renal failure

Puberty is a period of transition characterized by a sequence of profound physical and psychological changes leading to full sexual maturity. This process is driven and orchestrated by the awakening of the gonadotropic hormone axis. Chronic renal failure and its treatment may interfere with the onset and progress of puberty by numerous mechanisms including endocrine, metabolic and neuropsychological abnormalities, and drug effects. On average, the onset of puberty is delayed by 2 years in children with chronic renal failure, even after successful transplantation. Moreover, pubertal height gain is only 50% of that observed in healthy children. In this report, we discuss the endocrine mechanisms underlying these alterations and highlight new therapeutical options for pubertal growth failure.

Sexual dysfunction in uremia

In summary, sexual dysfunction is a common finding in both men and women with chronic renal failure. Common disturbances include erectile dysfunction in men, menstrual abnormalities in women, and decreased libido and fertility in both sexes. These abnormalities are primarily organic in nature and are related to uremia as well as the other comorbid conditions that frequently accompany the chronic renal failure patient. Fatigue and psychosocial factors related to the presence of a chronic disease are also contributory factors. Disturbances in the hypothalamic-pituitary-gonadal axis can be detected before the need for dialysis but continue to worsen once dialytic therapy is initiated. Impaired gonadal function is prominent in uremic men, whereas the disturbances in the hypothalamicpituitary axis are more subtle. By contrast, central disturbances are more prominent in uremic women. Therapy is initially directed toward optimizing the delivery of dialysis, correcting anemia with recombinant erythropoietin, and controlling the degree of secondary hyperparathyroidism with vitamin D. For many practicing nephrologists, sildenafil has become the first-line therapy in the treatment of impotence. In the hypogonadal man whose only complaint is decreased libido, testosterone may be of benefit. Regular gynecologic follow-up is required in uremic women to guard against potential complications of unopposed estrogen effect. Uremic women should be advised against pregnancy while on dialysis. Successful transplantation is the most effective means of restoring normal sexual function in both men and women with chronic renal failure.

Androgen therapy in chronic renal failure

Chronic renal failure, dialysis and transplantation have major effects on male reproductive health because of the impairment of spermatogenesis, steroidogenesis and sexual function. Hypothalamo-pituitary testicular dysfunction in uraemia is manifest clinically as delayed growth and puberty, sexual dysfunction, androgen deficiency, impaired spermatogenesis and infertility. Apart from renal anaemia, there are at present no proven indications for androgen therapy in chronic renal failure. This chapter reviews the basis and scope for various clinical applications of gonadotropin and androgen therapy as an adjunct to the standard medical care of chronic renal failure. The therapeutic possibilities implied by experimental and clinical findings suggesting that uraemic hypogonadism may be a functional state of gonadotropin deficiency are emphasized.

Central precocious puberty and chronic renal failure: a reversible condition post renal transplantation

A 3 year-old boy with chronic renal failure associated with prune belly syndrome who developed central precocious puberty is described. He had been maintained on cyclic peritoneal dialysis from age 13 months with creatinine levels of 400-600 mumol/l. Increased linear growth rate probably began at 18 months, and by 38 months of age he had testicular enlargement and pubic hair consistent with Tanner stage 2. Elevated levels of serum testosterone (3.6 nmol/l; normal < 0.7 nmol/l) and luteinizing hormone (LH) (2.8 IU/l; normal < 1.0 IU/l) were demonstrated with a pubertal response to luteinizing hormone-releasing hormone (LHRH) stimulation (peak LH 43.5 IU/l). Other endocrine tests demonstrated hyperprolactinemia (170 micrograms/l; normal 3.4-22 micrograms/l), but normal pituitary-thyroid and pituitary-adrenal functions and normal cranial MR imaging. Despite LHRH-agonist therapy with leuprolide over the next 8 months, he showed an incomplete response with only partial inhibition of basal LH and testosterone levels, and continued significant increments in height standard deviation scores (Ht-SDS) and bone age estimates. However, the sexual precocity appeared fully reversible following a successful living-related renal transplant at age 50 months. Despite discontinuation of leuprolide treatment post-operatively, there was a full reversal of his serum LH and testosterone to a prepubertal profile as well as normalization of the serum prolactin levels. Whereas most boys with chronic renal failure show delayed pubertal development and suppressed linear growth, our patient presents a unique phenomenon of reversible central precocious puberty. The effects of leuprolide therapy in the presence of a uremic milieu and the outcome of successful renal transplantation on sexual precocity are described.