Influence of renin-angiotensin system on serum parathyroid hormone levels in uremic patients. Clin Exp Nephrol. 2012;16:130-135. [PMID: 21912899 DOI: 10.1007/s10157-011-0534-x]

Angiotensin II Modulates Calcium/Phosphate Excretion in Experimental Model of Hypertension: Focus on Bone

A link between hypertension and long-term bone health has been suggested. The aim of this study was to investigate the effects of chronic angiotensin II administration on urinary calcium/phosphate excretion, bone mineral density, bone remodeling and osteoblast population in a well-established experimental model of hypertension, in the absence of possible confounding factors that could affect bone metabolism. Male Sprague-Dawley rats, divided in the following groups: (a) Angiotensin II (Ang II, 200 ng/kg/min, osmotic minipumps, sub cutis, n = 8); (b) Ang II+losartan (Los, 50 mg/kg/day, per os, n = 6); (c) control group (physiological saline, sub cutis, n = 9); and (d) control+losartan (n = 6) were treated for four weeks. During the experimental period, 24-hour diuresis, urinary calcium, phosphate and sodium excretion were measured prior to the treatment, at two weeks of treatment, and at the end of the treatment. Systolic blood pressure was measured by plethysmography technique (tail cuff method). At the end of the experimental protocol, the rats were euthanized and peripheral quantitative computed tomography at the proximal metaphysis and at the diaphysis of the tibiae and quantitative bone histomorphometry on distal femora were performed. Angiotensin II-dependent hypertension is associated with increased calcium and phosphate excretion. AT1 receptor blockade prevented the increase of blood pressure and phosphate excretion but did not affect the increase of calcium excretion. These changes took place without significantly affecting bone density, bone histology or osteoblast population. In conclusion, in our experimental conditions, angiotensin II-dependent hypertension gave rise to an increased urinary excretion of calcium and phosphate without affecting bone density.

Relationship between parathyroid hormone and renin-angiotensin-aldosterone system in hemodialysis patients with secondary hyperparathyroidism

INTRODUCTION

Hyperparathyroidism (HPT) is associated with mortality and cardiovascular disease (CVD) in dialysis patients. However, its mechanism is still unclear. It is suspected that parathyroid hormone (PTH) is associated with the renin-angiotensin-aldosterone system (RAAS) as a possible mechanism. Thus, we examined their hormonal interaction in hemodialysis patients with secondary HPT.

MATERIALS AND METHODS

Seventeen hemodialysis patients with HPT were included. All patients underwent total parathyroidectomy (PTx). Serum intact PTH (iPTH), calcium and phosphate levels, plasma renin activity (PRA), and plasma aldosterone levels (ALD) were measured pre- and post-PTx.

RESULTS

Pre-serum iPTH tended to be correlated with pre-PRA and were significantly correlated with pre-ALD (pre-PRA: r = 0.44, p = 0.07, pre-ALD: r = 0.49, p < 0.05). With the reduction in serum iPTH after PTx, PRA and ALD significantly decreased after PTx. Additionally, the change in serum iPTH tended to be correlated with the changes in PRA and ALD (PRA; r = 0.46, p = 0.05, ALD; r = 0.45, p = 0.06).

CONCLUSION

Our results suggest that PTH could be interrelated with RAAS in hemodialysis patients with secondary HPT.

The Interplay Between the Renin-Angiotensin-Aldosterone System and Parathyroid Hormone

The renin-angiotensin-aldosterone system (RAAS) is the regulatory system by which renin induces aldosterone production. Angiotensin II (Ang II) is the main effector substance of the RAAS. The RAAS regulates blood pressure and electrolyte balance by controlling blood volume and peripheral resistance. Excessive activation of the RAAS is an important factor in the onset of cardiovascular disease and the deterioration of this disease. The most common RAAS abnormality is primary aldosteronism (PA). Parathyroid hormone (PTH) is a peptide secreted by the main cells of the parathyroid gland, which promotes elevated blood calcium (Ca²⁺) levels and decreased blood phosphorus (Pi) levels. Excessive secretion of PTH can cause primary hyperparathyroidism (PHPT). Parathyroidism is highly prevalent in postmenopausal women and is often associated with secondary osteoporosis. PA and PHPT are common endocrine system diseases. However, studies have shown a link between the RAAS and PTH, indicating a positive relationship between them. In this review, we explore the complex bidirectional relationship between the RAAS and PTH. We also point out possible future treatment options for related diseases based on this relationship.

Circulating osteoprotegerin is associated with chronic kidney disease in hypertensive patients

Background

Osteoprotegerin (OPG) is a glycoprotein that plays an important regulatory role in the skeletal, vascular, and immune system. It has been shown that OPG predicts chronic kidney disease (CKD) in diabetic patients. We hypothesized that OPG could be a risk marker of CKD development also in non-diabetic hypertensive patients.

Methods

A case-control study was carried out to measure circulating OPG levels in 42 hypertensive patients with CKD and in 141 hypertensive patients without CKD. A potential relationship between OPG and the presence of CKD was investigated and a receiver-operating characteristic (ROC) curve was designed thereafter to identify a cut-off value of OPG that best explained the presence of CKD. Secondly, to evaluate whether OPG increase could affect the kidney, 18 C57BL/6J mice were randomized to be treated with saline or recombinant OPG every 3 weeks for 12 weeks.

Results

Circulating OPG levels were significantly higher in hypertensive patients with CKD, and there was a significant inverse association between OPG and renal function, that was independent from other variables. ROC analysis showed that OPG levels had a high statistically predictive value on CKD in hypertensive patients, which was greater than that of hypertension. The OPG best cut-off value associated with CKD was 1109.19 ng/L. In the experimental study, OPG delivery significantly increased the gene expression of pro-inflammatory and pro-fibrotic mediators, as well as the glomerular nitrosylation of proteins.

Conclusions

This study shows that OPG is associated with CKD in hypertensive patients, where it might have a higher predictive value than that of hypertension for CKD development. Secondly, we found that OPG delivery significantly increased the expression of molecular pathways involved in kidney damage. Further longitudinal studies are needed not only to evaluate whether OPG predicts CKD development but also to clarify whether OPG should be considered a risk factor for CKD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-017-0625-3) contains supplementary material, which is available to authorized users.

PTH Is a Promising Auxiliary Index for the Clinical Diagnosis of Aldosterone-Producing Adenoma

BACKGROUND

Parathyroid hormone (PTH) stimulates aldosterone secretion in human adrenocortex and is regulated by the renin-angiotensin-aldosterone system. We speculated that measurement of PTH may be a valuable aid in the diagnosis of aldosterone-producing adenoma (APA).

METHODS

To test this hypothesis, we recruited 142 patients with adrenal adenoma, of whom 84 had an APA and 58 had a nonfunctioning adrenal adenoma (NFA). Plasma levels of intact PTH, serum potassium, sodium, calcium, phosphate, 25(OH) vitamin D, plasma aldosterone concentration (PAC), plasma renin activity (PRA), and aldosterone to renin ratio (ARR) were measured in every patient. Computed tomography (CT) scanning of the adrenal gland and adrenal hormone levels was used to evaluate the function of the adrenal adenoma. We also evaluated the impact of renin-angiotensin-aldosterone system (RAAS) components on PTH from the recumbent-upright test in 15 patients with APA and 30 patients with NFA.

RESULTS

Compared with NFA, PTH levels were significantly increased in patients with APA, and serum calcium and phosphate were significantly decreased. When position was changed from supine to upright, the variation in PTH levels was significantly higher in APA patients compared with NFA patients. Receiver operator characteristic (ROC) curves identified the Youden index, which corresponded to the best tradeoff of combined marker (ARR and PTH) with a sensitivity and specificity of 89.3% and 93.1%, respectively.

CONCLUSIONS

The baseline and positional variation of serum PTH levels were significant in APA, thus PTH may be a promising auxiliary index for the clinical diagnosis of APA.

Aldosterone, parathyroid hormone, and the use of renin-angiotensin-aldosterone system inhibitors: the multi-ethnic study of atherosclerosis

CONTEXT

Aldosterone and PTH are implicated in the pathogenesis of cardiovascular and skeletal diseases. An expanding body of evidence supports a bidirectional and positive physiologic relationship between aldosterone and PTH. Large population-based studies confirming this relationship, and whether it may be targeted as a potential method to mitigate the clinical consequences associated with excess aldosterone and PTH, are needed.

OBJECTIVE

We hypothesized that higher aldosterone levels would associate with higher PTH, and that the use of renin-angiotensin-aldosterone system (RAAS) inhibitors would predict lower PTH in a large, multi-ethnic, community-based cohort.

DESIGN, SETTING, PARTICIPANTS

We conducted cross-sectional analyses of participants in the Multi-Ethnic Study of Atherosclerosis without apparent primary hyperparathyroidism or chronic kidney disease (n = 5668). We evaluated associations of RAAS inhibitor use with PTH concentration among 1888 treated hypertensive participants. We also tested associations of serum aldosterone concentration with PTH concentration among 1547 participants with these measurements.

OUTCOME

Serum PTH concentration.

RESULTS

Higher aldosterone associated with higher PTH (β = 0.19 pg/ml per 1 ng/dl of aldosterone, P < .0001), and this finding was most pronounced among those with a primary hyperaldosteronism-like phenotype. There was a stepwise increment in PTH when comparing untreated normotensives, hypertensives using RAAS inhibitors, untreated hypertensives, and treated hypertensives using non-RAAS inhibitors (40.8, 45.0, 46.2, 47.1 pg/ml, respectively). The use of any RAAS inhibitor independently associated with lower PTH (β = -2.327 pg/ml per use of RAAS inhibitor, P = .006), when compared with the use of any non-RAAS inhibitor medication.

CONCLUSIONS

Higher serum aldosterone concentration is associated with higher serum PTH concentration, and the use of RAAS inhibitors is associated with lower PTH concentration. These results extend prior evidence from observational and intervention studies suggesting a potentially important and modifiable relationship between the RAAS and PTH in humans.

The renin-angiotensin-aldosterone system and calcium-regulatory hormones

There is increasing evidence of a clinically relevant interplay between the renin-angiotensin-aldosterone system and calcium-regulatory systems. Classically, the former is considered a key regulator of sodium and volume homeostasis, while the latter is most often associated with skeletal health. However, emerging evidence suggests an overlap in regulatory control. Hyperaldosteronism and hyperparathyroidism represent pathophysiologic conditions that may contribute to or perpetuate each other; aldosterone regulates parathyroid hormone and associates with adverse skeletal complications, and parathyroid hormone regulates aldosterone and associates with adverse cardiovascular complications. As dysregulation in both systems is linked to poor cardiovascular and skeletal health, it is increasingly important to fully characterize how they interact to more precisely understand their impact on human health and potential therapies to modulate these interactions. This review describes the known clinical interactions between these two systems including observational and interventional studies. Specifically, we review studies describing the inhibition of renin activity by calcium and vitamin D, and a potentially bidirectional and stimulatory relationship between aldosterone and parathyroid hormone. Deciphering these relationships might clarify variability in outcomes research, inform the design of future intervention studies and provide insight into the results of prior and ongoing intervention studies. However, before these opportunities can be addressed, more effort must be placed on shifting observational data to the proof of concept phase. This will require reallocation of resources to conduct interventional studies and secure the necessary talent.

The effect of renin-angiotensin system inhibitors on intact parathyroid hormone levels in peritoneal dialysis patients

HYPOTHESIS/INTRODUCTION

The objective of this article is to investigate the effect of renin-angiotensin system inhibitors (RASIs) on intact parathyroid hormone (iPTH) levels in continuous ambulatory peritoneal dialysis (CAPD) patients.

MATERIALS AND METHODS

All patients were divided into RASI-treated and non-treated groups. The relationships between the iPTH levels in CAPD patients and the clinical parameters and medication use were analyzed via linear regression.

RESULTS

A total of 149 CAPD patients were included in this study. The average iPTH level of the entire group was 189.4 pg/ml (range, 102.8-373.4 pg/ml). There were 79 (53.0%) and 70 (47.0%) cases in the RASI-treated and non-treated groups, respectively, with average iPTH levels of 139.0 pg/ml (range, 91.6-258.4 pg/ml) and 253.0 pg/ml (range, 134.3-467.2 pg/ml), respectively; this difference was statistically significant (p = 0.001). Multilinear regression analysis showed that age, dialysis vintage, serum phosphatemia, ALP, Hb and RASI use were independent factors that were associated with iPTH level.

CONCLUSION

RASI use may be associated with a lower iPTH level in CAPD patients, although the underlying mechanism requires further study.

Interactions between adrenal-regulatory and calcium-regulatory hormones in human health

PURPOSE OF REVIEW

To summarize the evidence characterizing the interactions between adrenal-regulating and calcium-regulating hormones, and the relevance of these interactions to human cardiovascular and skeletal health.

RECENT FINDINGS

Human studies support the regulation of parathyroid hormone (PTH) by the renin-angiotensin-aldosterone system (RAAS): angiotensin II may stimulate PTH secretion via an acute and direct mechanism, whereas aldosterone may exert a chronic stimulation of PTH secretion. Studies in primary aldosteronism, congestive heart failure, and chronic kidney disease have identified associations between hyperaldosteronism, hyperparathyroidism, and bone loss, which appear to improve when inhibiting the RAAS. Conversely, elevated PTH and insufficient vitamin D status have been associated with adverse cardiovascular outcomes, which may be mediated by the RAAS. Studies of primary hyperparathyroidism implicate PTH-mediated stimulation of the RAAS, and recent evidence shows that the vitamin D-vitamin D receptor complex may negatively regulate renin expression and RAAS activity. Ongoing human interventional studies are evaluating the influence of RAAS inhibition on PTH and the influence of vitamin D receptor agonists on RAAS activity.

SUMMARY

Although previously considered independent endocrine systems, emerging evidence supports a complex web of interactions between adrenal-regulating and calcium-regulating hormones, with implications for human cardiovascular and skeletal health.

Potential pathophysiological role for the vitamin D deficiency in essential hypertension

Vitamin D deficiency has been indicated as a pandemic emerging public health problem. In addition to the well-known role on calcium-phosphorus homeostasis in the bone, vitamin D-mediated processes have been recently investigated on other diseases, such as infections, cancer and cardiovascular diseases. Recently, both the discovery of paracrine actions of vitamin D (recognized as “local vitamin D system”) and the link of vitamin D with renin-angiotensin-aldosterone system and the fibroblast growth factor 23/klotho pathways highlighted its active cardiovascular activity. Focusing on hypertension, this review summarizes the more recent experimental evidence involving the vitamin D system and deficiency in the cardiovascular pathophysiology. In particular, we updated the vascular synthesis/catabolism of vitamin D and its complex interactions between the various endocrine networks involved in the regulation of blood pressure in humans. On the other hand, the conflicting results emerged from the comparison between observational and interventional studies emphasize the fragmentary nature of our knowledge in the field of vitamin D and hypertension, strongly suggesting the need of further researches in this field.

Aldosterone and parathyroid hormone interactions as mediators of metabolic and cardiovascular disease

Inappropriate aldosterone and parathyroid hormone (PTH) secretion is strongly linked with development and progression of cardiovascular (CV) disease. Accumulating evidence suggests a bidirectional interplay between parathyroid hormone and aldosterone. This interaction may lead to a disproportionally increased risk of CV damage, metabolic and bone diseases. This review focuses on mechanisms underlying the mutual interplay between aldosterone and PTH as well as their potential impact on CV, metabolic and bone health. PTH stimulates aldosterone secretion by increasing the calcium concentration in the cells of the adrenal zona glomerulosa as a result of binding to the PTH/PTH-rP receptor and indirectly by potentiating angiotensin 2 induced effects. This may explain why after parathyroidectomy lower aldosterone levels are seen in parallel with improved cardiovascular outcomes. Aldosterone mediated effects are inappropriately pronounced in conditions such as chronic heart failure, excess dietary salt intake (relative aldosterone excess) and primary aldosteronism. PTH is increased as a result of (1) the MR (mineralocorticoid receptor) mediated calciuretic and magnesiuretic effects with a trend of hypocalcemia and hypomagnesemia; the resulting secondary hyperparathyroidism causes myocardial fibrosis and disturbed bone metabolism; and (2) direct effects of aldosterone on parathyroid cells via binding to the MR. This adverse sequence is interrupted by mineralocorticoid receptor blockade and adrenalectomy. Hyperaldosteronism due to klotho deficiency results in vascular calcification, which can be mitigated by spironolactone treatment. In view of the documented reciprocal interaction between aldosterone and PTH as well as the potentially ensuing target organ damage, studies are needed to evaluate diagnostic and therapeutic strategies to address this increasingly recognized pathophysiological phenomenon.

Human interventions to characterize novel relationships between the renin-angiotensin-aldosterone system and parathyroid hormone

Observational studies in primary hyperaldosteronism suggest a positive relationship between aldosterone and parathyroid hormone (PTH); however, interventions to better characterize the physiological relationship between the renin-angiotensin-aldosterone system (RAAS) and PTH are needed. We evaluated the effect of individual RAAS components on PTH using 4 interventions in humans without primary hyperaldosteronism. PTH was measured before and after study (1) low-dose angiotensin II (Ang II) infusion (1 ng/kg per minute) and captopril administration (25 mg×1); study (2) high-dose Ang II infusion (3 ng/kg per minute); study (3) blinded crossover randomization to aldosterone infusion (0.7 µg/kg per hour) and vehicle; and study (4) blinded randomization to spironolactone (50 mg/daily) or placebo for 6 weeks. Infusion of Ang II at 1 ng/kg per minute acutely increased aldosterone (+148%) and PTH (+10.3%), whereas Ang II at 3 ng/kg per minute induced larger incremental changes in aldosterone (+241%) and PTH (+36%; P<0.01). Captopril acutely decreased aldosterone (-12%) and PTH (-9.7%; P<0.01). In contrast, aldosterone infusion robustly raised serum aldosterone (+892%) without modifying PTH. However, spironolactone therapy during 6 weeks modestly lowered PTH when compared with placebo (P<0.05). In vitro studies revealed the presence of Ang II type I and mineralocorticoid receptor mRNA and protein expression in normal and adenomatous human parathyroid tissues. We observed novel pleiotropic relationships between RAAS components and the regulation of PTH in individuals without primary hyperaldosteronism: the acute modulation of PTH by the RAAS seems to be mediated by Ang II, whereas the long-term influence of the RAAS on PTH may involve aldosterone. Future studies to evaluate the impact of RAAS inhibitors in treating PTH-mediated disorders are warranted.