Total body zinc depletion and its relationship to the development of hyperprolactinemia in chronic renal insufficiency

Endocrine manifestations of chronic kidney disease and their evolving management: A systematic review

BACKGROUND

Chronic Kidney Disease (CKD) shows a wide range of renal abnormalities including the excretory, metabolic, endocrine, and homeostatic function of the kidney. The prognostic impact of the 'endocrine manifestations' which are often overlooked by clinicians cannot be overstated.

METHODS AND OBJECTIVES

A systematic review was attempted to provide a comprehensive overview of all endocrine abnormalities of CKD and their evolving principles of management, searching databases of PubMed, Embase, and Scopus and covering the literature between 2002 and 2022.

RESULTS

The endocrine derangements in CKD can be attributed to a myriad of pathologic processes, in particular decreased clearance, impaired endogenous hormone production, uremia-induced cellular dysfunction, and activation of systemic inflammatory pathways. The major disorders include anemia, hyperprolactinemia, insulin resistance, reproductive hormone deficiency, thyroid hormone deficiency, and serum FGF (Fibroblast Growth Factor) alteration. Long-term effects of CKD also include malnutrition and increased cardiovascular risk. The recent times have unveiled their detailed pathogenesis and have seen an evolution in the principles of management which necessitates a revision of current guidelines.

CONCLUSION

Increased advertence regarding the pathology, impact, and management of these endocrine derangements can help in reducing morbidity as well as mortality in the CKD patients by allowing prompt individualized treatment. Moreover, with timely and appropriate intervention, a long-term reduction in complications, as well as an enhanced quality of life, can be achieved in patients with CKD.

Erectile dysfunction in renal failure and transplant patients

Erectile dysfunction (ED) is a prevalent and pertinent condition in the chronic kidney disease (CKD) population. It has a multifactorial etiology, including disruptions of the hypothalamic-pituitary-gonadal axis, the endothelial paracrine signaling system, calcium and vitamin D homeostasis, along with several other factors. Efficacy of treatment of ED in the CKD population is comparable to non-CKD patients across multiple modalities, including PDE5 inhibitors, vacuum erectile devices, intracavernosal injections and penile prostheses. Renal transplant improves the contributing comorbid conditions that lead to ED in CKD patients; thus rates of ED are improved post-transplant. It is important to note that there is a small percentage of patients with persistent ED after renal transplantation.

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.

Chronic kidney disease and erectile dysfunction

Erectile dysfunction (ED) is a common condition among male chronic kidney disease (CKD) patients. Its prevalence is estimated to be approximately 80% among these patients. It has been well established that the production of nitric oxide from the cavernous nerve and vascular endothelium and the subsequent production of cyclic GMP are critically important in initiating and maintaining erection. Factors affecting these pathways can induce ED. The etiology of ED in CKD patients is multifactorial. Factors including abnormalities in gonadal-pituitary system, disturbance in autonomic nervous system, endothelial dysfunction, anemia (and erythropoietin deficiency), secondary hyperparathyroidism, drugs, zinc deficiency, and psychological problems are implicated in the occurrence of ED. An improvement of general conditions is the first step of treatment. Sufficient dialysis and adequate nutritional intake are necessary. In addition, control of anemia and secondary hyperparathyroidism is required. Changes of drugs that potentially affect erectile function may be necessary. Further, zinc supplementation may be necessary when zinc deficiency is suspected. Phosphodiesterase type 5 inhibitors (PDE5Is) are commonly used for treating ED in CKD patients, and their efficacy was confirmed by many studies. Testosterone replacement therapy in addition to PDE5Is may be useful, particularly for CKD patients with hypogonadism. Renal transplantation may restore erectile function. ED is an early marker of cardiovascular disease (CVD), which it frequently precedes; therefore, it is crucial to examine the presence of ED in CKD patients not only for the improvement of the quality of life but also for the prevention of CVD attack.

Erectile dysfunction in hemodialysis: A systematic review

Men with chronic renal failure (CRF) on hemodialysis have been frequently associated with erectile dysfunction (ED), with an of between 20% to 87.7%. As a result of the multi-system disease processes present in many uremic men, it is apparent that the pathogenesis of ED is most probably multifactorial. Factors to be considered include peripheral vascular disease, neurogenic abnormalities, hormonal disturbances and medications used for treatment of conditions associated with CRF. These physiological abnormalities may be supplemented by significant psychological stresses and abnormalities resulting from chronic illness. Treatment must start with the determination and treatment of the underlying causes. In addition to psychological treatment, further lines of treatment of ED in CRF can be classified as 1st line (medical treatment which includes oral phosphodiesterase-5 inhibitors and hormone regulation), 2nd line (intracavernosal injection, vacuum constriction devices and alprostadil urethral suppositories) or 3rd line (surgical treatment). Renal transplantation improves the quality of life for some patients with CRF and subsequently it may improve erectile function in a significant number of them, however still there is high incidence of ED after transplantation.

Prolactin levels, endothelial dysfunction, and the risk of cardiovascular events and mortality in patients with CKD

BACKGROUND AND OBJECTIVES

Both prolactin clearance and production are altered in CKD. In nonrenal populations, emerging evidence suggests that prolactin participates in the atherosclerotic process. Given the elevated cardiovascular risk of CKD, this study examined links between prolactinemia, vascular derangements, and outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational study was conducted in two cohorts: one with 457 nondialyzed CKD patients (mean age 52±12 years; 229 men) with measurements of flow-mediated dilation (FMD) and carotid intima-media thickness and one with 173 hemodialysis patients (65±12 years; 111 men) with measurements of pulse wave velocity (PWV). Patients were followed for cardiovascular events (n=146, nondialyzed cohort) or death (n=79, hemodialysis cohort).

RESULTS

Prolactin levels increased along with reduced kidney function. Prolactin significantly and independently contributed to explain the variance of both FMD (in nondialyzed patients) and PWV (in hemodialysis patients), but not intima-media thickness. In Cox analyses, the risk of cardiovascular events in nondialyzed patients increased by 27% (hazard ratio [HR], 1.27; 95% confidence interval [95% CI], 1.17-1.38) for each 10 ng/ml increment of prolactin. Similarly, the risk for all-cause and cardiovascular mortality in hemodialysis patients increased by 12% (HR, 1.12; 95% CI, 1.06-1.17) and 15% (HR, 1.15; 95% CI, 1.08-1.21), respectively. This was true after multivariate adjustment for confounders and after adjustment within the purported causal pathway (FMD or PWV).

CONCLUSIONS

Prolactin levels directly associated with endothelial dysfunction/stiffness and with increased risk of cardiovascular events and mortality in two independent cohorts of CKD patients.

Research on zinc blood levels and nutritional status in adolescents with autoimmune hepatitis

CONTEXT

Zinc deficiency in children and adolescents impairs their growing, development and immune system.

OBJECTIVES

To verify the existence of plasma and leukocyte zinc deficiency in adolescents with autoimmune hepatitis.

METHODS

The study comprised 23 patients with autoimmune hepatitis, aged 10-18 years, assisted at the Ambulatory Service of Pediatric Hepatology of the University of Campinas Teaching Hospital, Campinas, SP, Brazil, and adolescents with ages compatible with the patients' ages comprised the control group. Sample of blood in both groups was collected for the analyses of plasma zinc and leukocyte zinc by atomic absorption spectrophotometry, beyond the nutritional status was evaluated in each adolescent. The following statistical tests were used: Mann-Whitney, Spearman's correlation and interclass concordance analysis.

RESULTS

The significance level adopted was 5%. The average zinc level in plasma in patients was 71.91 ± 11.79 µg/dL and, in the control group, it was 80.74 ± 10.92 µg/dL, showing a significant difference (P = 0.04). The leukocyte zinc level in patients was 222.33 ± 166.13 pmol/10⁶ cells and, in the control group, it was 226.64 ± 217.81 pmol/10⁶ cells; there was no statistical significance between them (P = 0.45).

CONCLUSION

The evaluation of the nutritional status showed that eutrophy is prevalent in patients, and they presented a higher body fat value than the control group, with a significant difference. More research is needed with adolescents with autoimmune hepatitis regarding levels of essential micronutrients, such as zinc, because a good nutritional status can improve the prognostic of liver disease.

Deficiência de zinco em crianças e adolescentes com doenças hepáticas crônicas

OBJETIVO: Revisar as principais pesquisas referentes ao zinco e ao estado desse mineral em crianças e adolescentes com doenças hepáticas crônicas. FONTES DE DADOS: As palavras-chave "zinco", "hepatopatias", "criança" e "adolescente" foram inseridas nas bases de dados PubMed, SciELO e Web of Science. O critério de seleção compreendeu os artigos de origem nacional e internacional, preferindo-se aqueles publicados de 1998 a 2008, além de estudos mais antigos considerados clássicos. SÍNTESE DOS DADOS: O zinco é um mineral essencial para a saúde das crianças devido às suas inúmeras funções no organismo, dentre elas a atuação no sistema imune, o favorecimento do crescimento estatural e do desenvolvimento sexual e cognitivo. As crianças hepatopatas parecem estar mais suscetíveis à deficiência de zinco do que as saudáveis pelo fato de a doença no fígado alterar o metabolismo desse mineral, principalmente a sua distribuição aos tecidos e sua excreção. O nível de zinco no plasma parece ser baixo nesses pacientes, mas esse biomarcador não reflete o real estado de zinco no organismo e, além disso, a excreção urinária de zinco parece estar aumentada. CONCLUSÕES: É necessário um número maior de estudos sobre o estado de zinco em crianças e adolescentes com doenças hepáticas crônicas.

Mammary gland zinc metabolism: regulation and dysregulation

Zinc (Zn) is required for numerous metabolic processes serving both a structural and catalytic role. The mammary gland has a unique Zn requirement resulting from the need to also transfer an extraordinary amount of Zn into milk (~0.5-1 mg Zn/day) during lactation. Impairments in this process can result in severe Zn deficiency in the nursing offspring which has adverse consequences with respect to growth and development. Moreover, dysregulated mammary gland Zn metabolism has recently been implicated in breast cancer transition, progression and metastasis, thus there is a critical need to understand the molecular mechanisms which underlie these observations. Tight regulation of Zn transporting mechanisms is critical to providing an extraordinary amount of Zn for secretion into milk as well as maintaining optimal cellular function. Expression of numerous Zn transporters has been detected in mammary gland or cultured breast cells; however, understanding the molecular mechanisms which regulate mammary Zn metabolism as well as the etiology and downstream consequences resulting from their dysregulation is largely not understood. In this review, we will summarize the current understanding of the regulation of mammary gland Zn metabolism and its regulation by reproductive hormones, with a discussion of the dysregulation of this process in breast cancer.

Induction of Metallothionein in Mesothelial Cells by Zinc

Patients on peritoneal dialysis (PD) are exposed to peritoneal dialysis fluids with unphysiological properties. Local defense systems are of importance. In this respect, metallothionein (MT) might play an important role. Because nothing is known about the achievability of MT induction in peritoneum by zinc, we performed the following study. We investigated human peritoneal mesothelial cells (HPMC) from omentum and a mesothelioma cell (MTC) line after addition of zinc in concentrations from 35 to 350 microM. Measurements of MT-mRNA and protein (by immuncytochemistry [IHC], Western blots, and dot blots) were performed. Zinc caused a clear and highly significant fourfold increase of RNA in MTC and to a lower extent in HPMC (1.6-fold, P < 0.001). IHC demonstrated a clear induction in HPMC and MTC. Western and dot blots confirmed this and showed an increase of MT from 112-mg/g total protein (TP) to 410-mg/g TP. Zinc was able to upregulate MT significantly in HPMC and MTC on the RNA and protein level. Fourfold increases of MT were achievable.

Relationships among plasma zinc, plasma prolactin, milk transfer, and milk zinc in lactating women

The objective was to analyze interrelationships among plasma zinc (PZ), plasma prolactin (PRL), milk transfer, and milk zinc from a longitudinal study of lactating women with a range of zinc intakes. Sixteen of 26 women received a 15 mg/d zinc supplement, resulting in a significant increase in total zinc intake compared with nonsupplemented participants (P<.001). No significant differences in key variables were observed between the zinc-supplemented and non-zinc-supplemented women; data were thus combined. An inverse trend between PRL and PZ was observed at 0.5 (r=-.36, P=.08) and 7 months (r=-.38, P=.06). Correlations between PRL at 0.5 months and at 3, 5, and 7 months were significant (r>.50, P<.01). PRL concentrations and milk transfer were positively correlated at 5 (r=.67, P<.001) and 7 months (r=.53, P<.01), consistent with PRL role in lactation maintenance. Studies including zinc-deficient lactating women are required to clarify the interrelationships between zinc status and PRL secretion.

Hormonal adjuvants for the treatment of renal anaemia

Hormonal adjuvants, besides being erythropoietic agents, broaden the spectrum of therapeutic options for the treatment of the anaemia of chronic kidney disease (CKD). Lowering elevated parathyroid hormone levels by oral calcium supplementation and phosphate restriction, by varying dialysate calcium concentrations, by administration of vitamin D3 derivatives and, in the near future, by treatment with calcimimetics may prove efficient in some patients to fight extensive requirements of erythropoietic agents. Clinical evidence for a principal role of secondary hyperparathyroidism in resistance to erythropoietin, however, is lacking. Active vitamin D3 derivatives, in addition to their beneficial effects on secondary hyperparathyroidism, appear to exert a direct, stimulatory action on erythroid precursor cells and possibly also an inhibitory action on collagen synthesis by bone marrow stromal cells. Growth hormone (GH) induces insulin-like growth factor (IGF)-1, which in turn counteracts apoptosis similarly to erythropoietin, and fosters proliferation of burst- and colony-forming units-erythroid (BFU-E, CFU-E). If erythropoietic agents improve survival of CKD patients, a similar benefit should apply for strategies that increase synthesis and bioavailabilty of IGF-1. The latter appears to be reduced in CKD patients, and zinc supplementation potentially enhances it via an increase in free IGF-1. Finally, androgens also exert anti-anaemic effects. Nandrolone decanoate constitutes the only androgen currently applicable for selected male dialysis patients over the age of 50 years. It should not be given to women, however, because of serious side effects. Collectively, hormonal interventions offer the potential to reduce requirements of erythropoietic agents, and some may also improve physical performance.

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.

Maternal zinc deficiency raises plasma prolactin levels in lactating rats

There is an inverse relation between zinc (Zn) intake and plasma prolactin in men and nonpregnant women. Whether a relation exists in lactating women is unknown, despite the potential consequences of perturbations in prolactin regulation on lactation performance. We examined the effects of low Zn intake on prolactin concentration, the prolactin regulatory pathway in the pituitary gland, and lactation performance in lactating rats. Female rats were fed diets containing 7 (zinc deficient; ZD), 10 (marginally zinc deficient; MZD) or 25 mg Zn/kg (control) from 70 d preconception to lactation d 11. Rats were killed, pituitary glands dissected, and tissues and plasma collected and analyzed for prolactin concentration. Pituitary gland pituitary factor 1 (Pit-1), dopamine 2 receptor (D2R), and prolactin receptor mRNA expression were measured in the pituitary gland. Liver, mammary gland, plasma, and milk Zn were measured. Milk intake of the pups was also recorded. Plasma prolactin concentration was higher in rats fed the ZD (125.9 microg/L) diet compared with control rats (21.7 microg/L). Pituitary gland prolactin concentration was higher in rats fed the ZD diet (69.8 mg/g total protein) compared with controls (29.0 mg/g). Plasma Zn concentration was lower in rats fed the MZD and ZD diets, and mammary gland and milk Zn concentrations were lower in rats fed the ZD diet compared with control rats. Rats fed the ZD diet had lower D2R, prolactin receptor, and Pit-1 mRNA levels, whereas rats fed the MZD diet had lower prolactin receptor and Pit-1 mRNA levels compared with control rats. Milk intake was lower in pups of rats fed the MZD and ZD diets. Our results suggest that marginal Zn nutriture may compromise milk production despite increased prolactin levels. In addition, increased circulating prolactin concentration is not due to altered nursing behavior, but may be due to alterations in the prolactin regulatory pathway in the pituitary gland.

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.

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.