Serum lipoprotein disturbances in primary and secondary hyperparathyroidism and effects of parathyroidectomy

Normohormonal primary hyperparathyroidism: A systematic review and meta-analysis

OBJECTIVE

We aim to evaluate the body of evidence reporting on normohormonal primary hyperparathyroidism (NHpHPT) patients to help guide their diagnosis, characterization and treatment.

BACKGROUND

Normohormonal primary hyperparathyroidism is a term used to describe patients with a normal PTH and elevated calcium levels. There is limited understanding regarding the presentation and appropriate management of these patients.

METHODS

A systematic review was conducted: abstract and full-text screening were independently conducted by 2 investigators. Odds ratios (OR), standard mean differences (SMD) and 95% confidence intervals were calculated.

RESULTS

Twenty-two studies were identified. Patients with NHpHPT were more likely to present with lower PTH (p < 0.00001) and calcium (p < 0.00001) levels. Intraoperatively, the NHpHPT group was 1.8 times more likely to undergo bilateral neck exploration (BNE) and harbor multigland disease. The rates of surgical cure were 93% in the NHpHPT and 96% in the pHPT groups (p = 0.0003).

CONCLUSION

Symptomatic patients with NHpHPT benefit from parathyroidectomy with prolonged intraoperative PTH monitoring, and a low threshold for conversion to BNE.

Hypolipidemic Therapy and Chronic Kidney Disease: Effects on Cardiovascular Risks and Renal Dysfunction

Steady increase in the prevalence of chronic kidney disease (CKD) is a serious public health problem, since CKD potentially leads to the development of end-stage renal disease (ESRD) that requires high-cost replacement therapy and is closely associated with increased risk of developing cardiovascular diseases (CVD), which are the cause of death in most patients. Progression of renal dysfunction and development of CVD are significantly affected by hyper- and dyslipidemia. This review contains results of studies evaluating the effect of hypolipidemic therapy on reduction of cardiovascular risk and slowdown of renal dysfunction in patients with CKD at pre-dialysis and dialysis stages of renal failure, as well as in patients with kidney transplant. In addition, recommendations on nutrition and new therapeutic approaches to lipid-lowering therapy in patients with CKD, as well as prospects for the usage of new hypolipidemic drugs are also presented.

Effects of 1,25 (OH)2 D3 Treatment on Lipid Levels in Uremic Hemodialysis Patients

The aim of this study was to evaluate the effect of 1,25 (OH)2D3 treatment on lipid levels in uremic hemodialysis (HD) patients. Thirty-one HD patients who had never been treated with vitamin D nor related drugs and 12 healthy subjects with normal renal functions were studied. Uremic HD patients were randomly divided into two groups. Sixteen uremic HD patients were treated with oral calcitriol (0.5 μg/day) for 8 weeks. 13 uremic HD patients and 12 healthy subjects were given placebo. In all these cases before and after 8 weeks of treatments; serum total lipid, total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerid levels were determined. After calcitriol treatment, triglycerid levels were significantly decreased. But total lipid, cholesterol, HDL-cholesterol and LDL-cholesterol levels did not significantly change. In the other two groups there were no significant changes. These results show that calcitriol treatment has a positive effect on triglycerid levels in uremic HD patients. This effect of mechanism of calcitriol treatment has not been known yet. But it could be due to regulation carbohydrates metabolism and normalization of parathormone (PTH) levels.

Arteriosclerosis in Dialysis Patients

Arteriosclerosis is a constant problem in long-term hemodialysis patients. Computer tomography of the abdominal aorta allows a well-defined and reproducible evaluation of aortosclerosis. In the cross-sectional study, aortosclerosis was significantly accelerated in 84 chronic hemodialysis patients and was comparable to the results found in 20-year older control patients without renal disease. The increase of aortosclerosis correlated significantly with age of the patient, smoking, and duration of dialysis therapy. Furthermore, increased VLDL cholesterol and decreased HDL cholesterol seem to enhance aortosclerosis in our dialysis patients. In the longitudinal study (two CT scans with a time interval of 87 ± 62.7 months) in 36 dialysis patients, progressed aortosclerosis correlated significantly with the long duration of hypertriglyceridemia, VLDL cholesterol, uric acid, and calcium phosphate products. Progression of aortosclerosis was reduced in parathyroidectomized patients. The study suggests that premature aortosclerosis is found in dialysis patients. In addition to the common risk factor of aortosclerosis, disturbed calcium phosphate and parathyroid hormone metabolism seem to enhance aortosclerosis in patients under maintenance hemodialysis.

Association of Triglyceride-Related Genetic Variants With Mitral Annular Calcification

BACKGROUND

Mitral annular calcium (MAC), commonly identified by cardiac imaging, is associated with cardiovascular events and predisposes to the development of clinically important mitral valve regurgitation and mitral valve stenosis. However, its biological determinants remain largely unknown.

OBJECTIVES

The authors sought to evaluate whether a genetic predisposition to elevations in plasma lipids is associated with the presence of MAC.

METHODS

The authors used 3 separate Mendelian randomization techniques to evaluate the associations of lipid genetic risk scores (GRS) with MAC in 3 large patient cohorts: the Framingham Health Study, MESA (Multiethnic European Study of Atherosclerosis), and the AGE-RS (Age, Gene/Environment Susceptibility-Reykjavik Study). The authors provided cross-ethnicity replication in the MESA Hispanic-American participants.

RESULTS

MAC was present in 1,149 participants (20.4%). In pooled analyses across all 3 cohorts, a triglyceride GRS was significantly associated with the presence of MAC (odds ratio [OR] per triglyceride GRS unit: 1.73; 95% confidence interval [CI]: 1.24 to 2.41; p = 0.0013). Neither low- nor high-density lipoprotein cholesterol GRS was significantly associated with MAC. Results were consistent in cross-ethnicity analyses among the MESA Hispanic-Americans cohort (OR per triglyceride GRS unit: 2.04; 95% CI: 1.03 to 4.03; p = 0.04). In joint meta-analysis across all included cohorts, the triglyceride GRS was associated with MAC (OR per triglyceride GRS unit: 1.79; 95% CI: 1.32 to 2.41; p = 0.0001). The results were robust to several sensitivity analyses that limit both known and unknown forms of genetic pleiotropy.

CONCLUSIONS

Genetic predisposition to elevated triglyceride levels was associated with the presence of MAC, a risk factor for clinically significant mitral valve disease, suggesting a causal association. Whether reducing triglyceride levels can lower the incidence of clinically significant mitral valve disease requires further study.

The impact of parathyroidectomy on serum ADAMTS1, ADAMTS4 levels, insulin resistance, and subclinical cardiovascular disease in primary hyperparathyroidism

PURPOSE

Primary hyperparathyroidism has been associated with increased incidence of morbidity and mortality of the cardiovascular system. The etiopathogenetic mechanisms underlying this association are still not completely clear. Accumulating evidence suggested that a disintegrin and metalloproteinase with thrombospondin-like motifs (ADAMTS) has a role in the development of inflammation and atherosclerosis. In this study, we aimed to determine whether there is a change in serum levels of ADAMTS1, ADAMTS4, carotid intima-media thickness, and cardiovascular risk score after the surgery and also whether there is a relationship between ADAMTS levels and cardiovascular risk score in hypercalcemic primary hyperparathyroidism patients.

METHODS

The study included the 48 consecutive newly diagnosed patients with primary hyperparathyroidism. The patients were evaluated before and six months after parathyroidectomy. The Framingham score is used to calculate cardiovascular risk. Serum ADAMTS levels were determined by a human enzyme-linked immunoassay in all subjects.

RESULTS

The fasting glucose, fasting insulin levels and HOMA values were decreased significantly in all patients after surgery compared to the pretreatment values (p < 0.05). ADAMTS1, ADAMTS4, and carotid intima-media thickness levels were significantly lower after surgical correction of primary hyperparathyroidism compared to the preoperative values (p < 0.05). cardiovascular risk score was decreased after parathyroidectomy however, the difference were not statistical significant (p > 0.05). There were statistically significant relationship between cardiovascular risk score and waist/hip ratio, calcium, LDL-cholesterol, carotid intima-media thickness, ADAMTS4 values.

CONCLUSION

Based on the results of the present study, fasting glucose, fasting insulin levels, ADAMTS1, ADAMTS4, and carotid intima-media thickness might be an additional parameters during the management of patients with primary hyperparathyroidism, since these factors might improve after surgery.

Lipid disorders in patients with renal failure: Role in cardiovascular events and progression of chronic kidney disease

The spectrum of lipid disorders in chronic kidney disease (CKD) is usually characterized by high triglycerides and reduced high dense lipoprotein (HDL), associated with normal or slightly reduced low dense lipoprotein (LDL)-cholesterol. This dyslipidemia is associated with an increased risk for atherosclerotic cardiovascular disease. Keys for the cardiovascular risk reduction in these patients are lowering the number and modifying the composition of the cholesterol-carrying atherogenic lipoprotein particles. Statins have an important role in primary prevention of cardiovascular events and mortality in non-hemodialyzed CKD patients. The benefits in terms of progression of renal failure are contradictory. Patient education regarding dietary regimen should be part of the CKD clinical management.

The Effect of Omega-3 Supplement on Serum Lipid Profile in Patients Undergoing Hemodialysis: A Randomized Clinical Trial

BACKGROUND

Some recent suggestions could show omega-3 condition deficiency following prolonged hemodialysis; however, these claims and speculations have not been well demonstrated with sufficient evidences. Hence, we attempted to assess the beneficial effects of omega-3 on lipid profile in patients with end-stage renal disease (ESRD) undergoing hemodialysis.

METHODS

One hundred and seventeen ESRD patients who were on maintenance dialysis in Rasoul-e-Akram and Madaen Hospitals were enrolled in this randomized clinical trial. These patients were divided into two groups randomly using block randomization method (57 patients as the case group receiving omega-3 for 12 weeks and 60 as the control group). Blood sample was taken from all patients for measurement of lipid profile, serum hemoglobin, and C-reactive protein at baseline as well as after the completion of interventions (after 12 weeks).

RESULTS

The average change in the value of HDL-C was significantly more in the patients who received omega-3 than in the control group (MD, -7 mg/dL; 95% CI, -11 to 0 p = 0.000). Also, the reduction in serum creatinine level was more in the omega-3 group than in the control group (MD, 0.7 mg/dL; 95% CI, -0.4 to 2.1 p = 0.023). The change in other indices including serum triglyceride, total cholesterol, and serum hemoglobin levels was not different between the two groups. The multivariable linear regression analysis showed no difference in serum HDL level between the two groups adjusted for sex, age, and time of dialysis, while the level of serum HDL-C could be adversely predicted by duration time. Similar regression model showed a between-group difference in serum creatinine in the presence of potential confounders.

CONCLUSION

The change in serum HDL level following use of omega-3 supplement is influenced by time of dialysis, not by drug effect. However, consumption of omega-3 can significantly reduce serum creatinine.

Reduced Stroke Risk After Parathyroidectomy in End-Stage Renal Disease: A 13-Year Population-Based Cohort Study

Research information on the risk of stroke in patients with dialysis-dependent end-stage renal disease (ESRD) who have undergone parathyroidectomy (PTX) is scant. We used a nationwide health insurance claims database to select all patients with dialysis-dependent ESRD age 18 years and older for the study population. Of the patients with ESRD, we selected 1083 patients who had undergone PTX between 1998 and 2006 as the PTX group and frequency-matched 1083 patients with ESRD by sex, age, years since the disease diagnosis, and the year of undergoing PTX as the non-PTX group. We used a multivariate Cox proportional hazards regression analysis to measure the risk of stroke for the PTX group compared with the non-PTX group after adjusting for sex, age, premium-based income, urbanization, and comorbidity. The mean follow-up periods were 6.08 and 5.38 years for the PTX and non-PTX groups, respectively. After adjusting for previously mentioned variables, significant risk reductions of stroke (adjusted hazard ratio = 0.57, 95% confidence interval = 0.41-0.79), particularly those of hemorrhagic stroke (adjusted hazard ratio = 0.34, 95% confidence interval = 0.20-0.57), with PTX were observed. Chronologically, the risk of stroke in the PTX group decreased in the second year after PTX and persisted for >3 years. PTX reduces the risk of stroke, particularly that of hemorrhagic stroke, in patients with dialysis-dependent ESRD. Other factors for risk reduction include sex (females), an age <65 years, and the presence of comorbidity.

Lipid abnormalities in kidney disease and management strategies

Patients with kidney diseases continue to experience significant cardiovascular disease (CVD) morbidity and mortality. Although there are many important risk factors playing a role in the pathogenesis of CVD in chronic kidney disease (CKD) patients, dyslipidemia (elevated triglycerides, elevated oxidized low-density lipoprotein and low/dysfunctional low high-density) represents one of the modifiable risk factors. Renal failure patients have unique lipid abnormalities which not only have complex role in pathogenesis of CVD but also cause relative resistance to usual interventions. Most of the randomized trials have been in hemodialysis population and data from CKD non-dialysis, peritoneal dialysis and renal transplant populations is extremely limited. Compared to general population, evidence of mortality benefit of lipid lowering medications in CKD population is scarce. Future research should be directed towards establishing long term benefits and side effects of lipid lowering medications, through randomized trials, in CKD population.

Dramatic alteration of the skull in a uremic patient with leontiasis ossea

The craniofacial skeleton represents a peculiar target of hyperparathyroidism in patients with end-stage renal disease who exhibit a dramatic pattern of uremic leontiasis ossea. Scant information regarding this condition is available in the renal literature, as the extreme and typical manifestations of leontiasis ossea have been described in only a small series of patients. We herein report a case of significant amelioration of massive modification of the facial appearance of a 30-year-old uremic Chinese woman with severe skeletal deformities who underwent total parathyroidectomy with a forearm autograft concurrently with effective drug treatment. This report may shed light on how to better understand and treat this metabolic derangement.

Parathyroidectomy improves survival in patients with severe hyperparathyroidism: a comparative study

Background and objectives

Secondary hyperparathyroidism (SHPT) in CKD is associated with an increased risk for mortality, but definitive data showing that parathormone control decreases mortality is still lacking. This study aimed to compare the mortality of patients with severe SHPT submitted to parathyroidectomy(PTX) with those who did not have access to surgery.

Methods

This is a retrospective study in a cohort of 251 CKD patients with severe SHPT who were referred to a CKD-MBD Center for PTX from 2005 until 2012.

Results

Most of our patients had indication of PTX, but only 49% of them had access to this surgical procedure. After a mean follow-up of 23 months, 72 patients had died. Non-survivors were older; more often had diabetes, lower serum 25 vitamin D and mostly had not been submitted to surgery. The relative risk of death was lower in the PTX patients (0.428; 95% CI, 0.28 to 0.67; p<0.0001). After adjustments, mortality risk was dependent on age (1.04; 95% CI, 1.01 to 1.07; p = 0.002), 25 vitamin D (0.43; 95% CI, 0.24 to 0.81; p = 0.006) and no access to PTX (4.13; 95% CI, 2.16 to 7.88; p<0.0001). Results remained the same in a second model using the PTX date as the study start date for the PTX group.

Conclusions

Our data confirms the benefit of PTX on mortality in patients with severe SHPT. The high mortality encountered in our population is significant and urges the need to better treat these patients.

Comparison of the Elecsys PTH(1-84) assay with four contemporary second generation intact PTH assays and association with other biomarkers in chronic kidney disease patients

OBJECTIVES

The COBAS Elecsys PTH(1-84) assay is a novel, electro-chemiluminescence immunoassay that exclusively measures full-length parathyroid hormone (PTH). The aim of this study is to compare the automated biointact Elecsys PTH(1-84) assay with four contemporary, iPTH assays in chronic kidney disease (CKD) patients.

DESIGN AND METHODS

We compared the Elecsys PTH(1-84) assay with four iPTH assays (Siemens ADVIA Centaur, Ortho Clinical Diagnostics (OCD) VITROS, Beckman Access2, Abbott ARCHITECT) in the measurement of PTH in 83 local CKD patients. Majority of the patients (44) had CKD but were not on dialysis, 15 were on hemodialysis, 15 were on peritoneal dialysis, and 9 were post-renal transplant. The precision performance and correlation of the assays were determined. PTH(1-84) concentrations were correlated with calcium, phosphate, alkaline phosphatase, hemoglobin, HbA1c and lipid concentrations.

RESULTS

The Elecsys PTH(1-84) assay showed comparable precision and good correlation with the iPTH assays. Although the four different iPTH assays correlated well with each other, there was significant discrepancy among assays. The discrepancy among assays increased with increasing PTH concentrations. The ADVIA Centaur and ARCHITECT assays measured significantly higher PTH concentrations than the VITROS and Access2 assays. PTH(1-84) showed a positive association with phosphate and alkaline phosphatase and an inverse association with HbA1c. There was no significant association with lipid concentrations.

CONCLUSIONS

The third generation Elecsys PTH(1-84) assay had comparable precision performance and correlated well with second generation iPTH assays. However, significant discrepancy was found among the four iPTH assays in measuring iPTH in CKD patients.

Improved long-term survival of dialysis patients after near-total parathyroidectomy

BACKGROUND

Severe secondary hyperparathyroidism, which is associated with life-threatening complications, can develop in dialysis-dependent end-stage renal disease patients. The aim of this study was to compare short- and long-term mortality in dialysis patients who underwent near-total parathyroidectomy (NTPTX) and matched nonoperated controls.

STUDY DESIGN

We identified 150 dialysis patients who underwent NTPTX (1993-2009) at our institution and compared them with 1,044 nonoperated control patients identified in the US Renal Data System registry, matched for age, sex, race, diabetes as cause of kidney failure, years on dialysis, and dialysis modality. Survival outcomes were estimated using multivariable Cox proportional hazards models with stratification on the matching sets, adjusted for cardiovascular comorbidities, smoking, inability to ambulate/transfer, and payor status.

RESULTS

During a follow-up of a mean of 3.6 years (range 0.1 month to 16.4 years), NTPTX patients had a significant reduction in the long-term risk of all-cause death (hazard ratio = 0.68; 95% CI, 0.52-0.89; p = 0.006) compared with controls. Thirty-day mortality rates for NTPTX patients and controls were 246 vs 105 per 1,000 person-years (p = 0.21). In adjusted analyses, NTPTX patients had a 37% reduced risk of all-cause death and a 33% reduced risk of cardiovascular death compared with controls. A durable reduction in mean parathyroid hormone was observed after NTPTX; from 1,776 ± 1,416.6 pg/mL to 301 ± 285.7 pg/mL (p < 0.0001).

CONCLUSIONS

In our center, NTPTX in dialysis patients was associated with a significant reduction in long-term risk of death compared with matched control patients, without a significantly increased short-term risk.

Survival after Parathyroidectomy in Patients with End-stage Renal Disease and Severe Hyperparathyroidism

BACKGROUND

Patients with end-stage renal disease (ESRD) and secondary hyperparathyroidism (SHPT) are at high risk of mortality. Whether an increased risk of death persists after a parathyroidectomy (PTX) is not clearly established.

SUBJECTS AND METHODS

The survival of 40 patients with ESRD and SHPT who underwent PTX was compared with that of 664 ESRD patients.

RESULTS

From first dialysis, a lower mortality rate was found in the group of patients who underwent PTX than in the nonoperated ESRD group (hazard ratio: 0.23; 95% CI: 0.14-0.37). The patients who underwent PTX were younger, had a longer time on dialysis, and had a higher prevalence of kidney transplantation. The mean number of comorbidities was lower (Charlson score 4.2 +/- 2.1 versus 6.4 +/- 2.9, p < 0.001). Then, we randomly selected two matched controls for each PTX case (80 controls, 40 PTX) who had at least an equivalent mean duration of dialysis between the first dialysis and PTX of the PTX group. In a univariate model, there was a trend for PTX being associated with prolonged survival. The mortality was higher both among those at an advanced age and those with a high Charlson score. Adjustments for these covariates made the effect of PTX no more significant.

CONCLUSIONS

The risk of death of patients with severe SHPT leading to PTX differed from that of nonoperated subjects. The apparent differences in survival may be related to the number and severity of associated comorbidities. ESRD patients who undergo PTX may represent a subset of healthier subjects.

Association between primary hyperparathyroidism and increased body weight: a meta-analysis

Although primary hyperparathyroidism is frequently asymptomatic, it has been associated with an increased prevalence of hypertension, insulin resistance, dyslipidemia, cardiovascular mortality, and cancer. Previously we reported that patients with primary hyperparathyroidism are heavier than age-matched controls. Increased body weight could contribute to the association between primary hyperparathyroidism and these extraskeletal complications. We searched MEDLINE for English language studies published between 1975 and 2003 that reported body weight or body mass index in subjects with primary hyperparathyroidism and a healthy age- and sex-comparable eucalcemic control group. Seventeen eligible studies were identified. Subjects with primary hyperparathyroidism were 3.34 kg (95% confidence interval, 1.97-4.71; P < 0.00001) heavier than controls in 13 studies reporting body weight. In four studies reporting body mass index, subjects with primary hyperparathyroidism had an increased body mass index of 1.13 kg/m(2) (-0.29 to 2.55; P = 0.12) compared with controls. Standard mean difference analysis showed that subjects with primary hyperparathyroidism had an increased weight or body mass index of 0.3 sd (0.19-0.40; P < 0.00001) compared with controls. We conclude that patients with primary hyperparathyroidism are heavier than their eucalcemic peers, and that increased body weight may contribute to the reported associations between primary hyperparathyroidism and some extraskeletal complications.

Beneficial effects of calcimimetics on progression of renal failure and cardiovascular risk factors

In renal failure, parathyroid hormone (PTH) is not only involved in the genesis of disturbed calcium/phosphate metabolism and ostitis fibrosa; it is also a permissive factor in the genesis of hypertension, cardiovascular damage, and dyslipidemia. The allosteric activator of the calcium sensing receptor NPSR-568 (R-568) has been shown to reduce the serum intact PTH (iPTH) concentration in uremic rats. It was the purpose of this study in subtotally nephrectomized (SNX) rats to compare pharmacologic abrogation of secondary hyperparathyroidism by R-568 with parathyroidectomy (PTX). The effects on progression of renal failure, BP, and lipid and structural parameters of kidney and heart were studied. Four groups of male SD-rats were studied: (1) sham-operated + vehicle-treated rats (controls); (2) SNX + vehicle-treated rats (SNX); (3) parathyroidectomized SNX + vehicle-treated rats (SNX+PTX); and (4) SNX + calcimimetic R-568-treated rats (SNX+R-568). R-568 (50 micro mol/kg per d) was administered by gavage. Eight weeks after SNX, serum creatinine concentration, urinary albumin excretion, BP, and serum LDL-cholesterol concentration were significantly lower in both R-568-treated and parathyroidectomized SNX compared with vehicle-treated SNX. In addition, structural abnormalities of the kidney (glomerulosclerosis, tubulointerstitial changes) and the heart (interstitial fibrosis, capillary length density, arteriolar wall thickness) were significantly less pronounced than in vehicle-treated SNX. It is concluded that in experimental renal failure abrogation of hyperparathyroidism by administration of a calcimimetic or PTX similarly attenuates progression of renal failure. Furthermore, it interferes with the development of cardiovascular risk factors and cardiac remodeling.

Normalized dyslipidaemia after parathyroidectomy in mild primary hyperparathyroidism: population-based study over five years

OBJECTIVE

Postmenopausal women are at increased risk of primary hyperparathyroidism (pHPT). Secondary dyslipidaemia in pHPT has attracted little attention, although morbidity and mortality associated with cardiovascular diseases have been reported to be increased in these patients.

DESIGN

A population-based screening programme was used to recruit postmenopausal women with mild, asymptomatic pHPT (mean serum calcium 2.57 +/- 0.12 mmol/l) and matched controls. MEASUREMENTS AND PATIENTS: Serum lipids, lipoprotein fractions and influences of treatment for the parathyroid disease were studied in 87 case-control pairs (mean age 67 years), 69 of whom completed a 5-year follow-up period.

RESULTS

pHPT was characterized by decreased serum high-density lipoprotein (HDL)-cholesterol, increased total triglycerides, very-low-density lipoprotein (VLDL)-triglycerides and VLDL-cholesterol levels and an elevated atherogenic index. The differences were more pronounced in the cases with serum parathyroid hormone levels in the normal range and were inversely correlated to the serum parathyroid hormone level. Parathyroidectomy, with or without additive hormone replacement therapy, normalized the dyslipidaemia. Five-year surveillance of pHPT without treatment was associated with a maintained increase in total triglycerides and the atherogenic index and a decrease in HDL-cholesterol levels.

CONCLUSION

Proatherosclerotic dyslipidaemia characterizes mild pHPT and is effectively reversed by parathyroidectomy. As dyslipidaemia might contribute to the increased risk of cardiovascular diseases and death observed in pHPT, the findings favour operative intervention rather than conservative surveillance in mild, asymptomatic pHPT in postmenopausal females.

Antagonistic effects of vitamin D and parathyroid hormone on lipoprotein lipase in cultured adipocytes

The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (calcitriol) and parathyroid hormone (PTH) on synthesis and secretion of lipoprotein lipase (LPL) were studied in 3T3-L1 adipocytes. Expression of the vitamin D receptor was demonstrated by saturation kinetics with radiolabeled calcitriol. Incubation with calcitriol (10(-8) M) for up to 4 d resulted in a time-dependent significant increase in heparin-releasable LPL activity (LPLa) accompanied by a significant increase in LPL mRNA. In contrast, incubation with intact (1-84) PTH (10(-6) to 10(-9) M) produced a time- and dose-dependent significant decrease in LPLa, but no change in LPL mRNA. The effect of PTH (24-h incubation, 10(-8) M) could be prevented by the calcium channel blocker verapamil. Coincubation with both calcitriol and PTH at equimolar concentration (10(-8) M) resulted in an increase in LPLa and LPL mRNA. These data indicate an antagonistic role for calcitriol and PTH in the regulation of LPL, possibly mediated by intracellular calcium, which may contribute to the alterations in lipoprotein metabolism occurring in uremia.

Parathyroid hormone, vitamin D, and cardiovascular disease in chronic renal failure

BACKGROUND

Parathyroid hormone and vitamin D have been shown to influence cardiac and vascular growth and function experimentally in human subjects with normal renal function. Because of the increased prevalence of hyperparathyroidism and altered vitamin D status in chronic renal failure, these alterations have been considered to contribute to the increased prevalence of cardiovascular disease and hypertension seen in this patient population. Methods and Results. In this article, we review experimental and clinical literature on the cardiovascular effects of parathyroid hormone and vitamin D and relate them to the development of cardiac and vascular dysfunction in uremia, such as: cardiomyopathy, myocardial hypertrophy, and fibrosis, as well as to myocardial ischemia; uremic glucose intolerance, dyslipidemia, and atherosclerosis; hypertension; and vascular and cardiac calcifications.

CONCLUSIONS

The hyperparathyroid state and altered vitamin D status found in uremia contribute to the cardiovascular pathology seen clinically in uremia and also to the excess mortality from cardiovascular causes found in this patient group. The therapeutic implications of these observations are also discussed.

Pathogenesis of dyslipoproteinemia in renal insufficiency: the role of lipoprotein lipase and hepatic lipase

The lipoprotein pattern, observed in patients with renal failure, suggests impaired catabolism of triglyceride-rich lipoproteins. This is supported by the findings of numerous studies addressing the pathogenesis of the dyslipoproteinemia of uremia. Aberrant lipoprotein composition, resulting in disturbed substrate characteristics for lipoprotein lipase and unfavourable receptor ligand function, probably constitutes the primary pathology. The structural details of the lipoproteins that are responsible for this dysfunction are not yet established. In this regard, abnormal apolipoprotein pattern and, possibly more important, biological modifications must be taken into consideration. Low activity of lipoprotein lipase does not seem to be a primary pathogenetic factor. However, there is little doubt that it plays a contributory part. The role of hepatic lipase is controversial.

Excess parathyroid hormone adversely affects lipid metabolism in chronic renal failure

Hyperlipidemia is common in chronic renal failure (CRF), but the underlying mechanisms are not clearly defined. Certain data points toward a potential role for the state of secondary hyperparathyroidism of CRF in its pathogenesis. We examined the effects of parathyroid hormone (PTH) on lipid metabolism utilizing intravenous fat tolerance test (IVFTT) and post-heparin lipolytic activity in five normal dogs, in six animals with CRF and secondary hyperparathyroidism (NPX) and in six normocalcemic-thyroparathyroidectomized dogs (NPX-PTX) with comparable degree and duration of CRF. NPX dogs had fasting hypertriglyceridemia (82 + 6.0 mg/dl vs. 49 +/- 2.7 mg/dl in normal dogs, P less than 0.01), abnormal IVFTT, and reduced post-heparin plasma LPL activity (151 +/- 10 vs. 275 +/- 15 mumol fatty acids/ml/min in normal dogs, P less than 0.01). The NPX-PTX dogs had normal fasting levels of serum triglycerides (42 +/- 0.6 mg/dl), normal IVFTT, and normal post-heparin plasma LPL (317 +/- 19 mumol fatty acids/ml/min) despite CRF. Post-heparin HL activity in plasma was not different between NPX and NPX-TPX dogs. The results show that excess blood levels of PTH and not other consequences of CRF are mainly responsible for the abnormalities in lipid metabolism. The data are consistent with the notion that excess PTH reduces post-heparin LPL activity in plasma, which in turn results in impaired lipid removal from the circulation and consequently hyperlipidemia.