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

Corticosteroid rhythms in hypoparathyroid patients

OBJECTIVE

Previous studies indicate a possible bidirectional stimulatory relationship between parathyroid hormone (PTH) and adrenocortical hormones, but the pattern of adrenocortical secretion in hypoparathyroidism is unknown. We aimed to characterize the adrenocortical secretion in patients with postsurgical hypoparathyroidism, and whether continuous subcutaneous PTH (1-34) infusion alters secretion patterns.

DESIGN

Crossover interventional study.

METHODS

We recruited 10 patients with postsurgical hypoparathyroidism with very low PTH levels on stable treatment with active vitamin D and calcium. Cortisol, cortisone, and aldosterone levels were measured in microdialysate from subcutaneous tissue over 24 h, before and during continuous subcutaneous PTH (1-34) infusion. Cortisol was also assayed in serum, saliva, and urine, and aldosterone and ACTH in serum and plasma, respectively. Ten patients with primary hyperparathyroidism and 10 healthy volunteers matched for sex and age served as controls.

RESULTS

Hypoparathyroid patients displayed both ultradian and circadian rhythmicity for tissue cortisol, cortisone, and aldosterone. Tissue aldosterone and cortisone levels were significantly lower in hypoparathyroid patients than in healthy controls, with no difference in tissue cortisol, but a higher cortisol to cortisone ratio. Treatment with PTH (1-34) increased tissue levels of aldosterone, cortisol, and cortisone and reduced the ratio of cortisol to cortisone.

CONCLUSION

Adrenocortical hormone levels are reduced in postsurgical hypoparathyroidism, and partly restored by short-term continuous subcutaneous PTH (1-34) therapy.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02986607.

Saline suppression testing-induced hypocalcemia and implications for clinical interpretations

BACKGROUND

Extracellular calcium critically regulates physiologic aldosterone production. Moreover, abnormal calcium flux and signaling are involved in the pathogenesis of the majority of primary aldosteronism cases.

METHODS

We investigated the influence of the saline suppression test (SST) on calcium homeostasis in prospectively recruited participants (n = 86).

RESULTS

During SST, 100% of participants had decreases in serum calcium, with 48% developing frank hypocalcemia. Serum calcium declined from 2.30 ± 0.08 mmol/L to 2.13 ± 0.08 mmol/L (P < .001) with parallel increases in parathyroid hormone from 6.06 ± 2.39 pmol/L to 8.13 ± 2.42 pmol/L (P < .001). In contrast, serum potassium and bicarbonate did not change, whereas eGFR increased and serum glucose decreased (P < .001). Lower body surface area (translating to greater effective circulating volume expansion during SST) was associated with greater reductions in (β = .33, P = .001), and absolutely lower, serum calcium levels (β = .25, P = .001). When evaluating clinically-relevant diagnostic thresholds, participants with post-SST aldosterone levels <138 pmol/L had lower post-SST calcium and 25-hydroxyvitamin D levels (P < .05), and higher post-SST parathyroid hormone levels (P < .05) compared with those with post-SST aldosterone levels >277 pmol/L.

CONCLUSION

SST uniformly decreases serum calcium, which is likely to be due to the combination of variable dilution, increased renal clearance, and vitamin D status. These acute reductions in bioavailable calcium are associated with lower post-SST aldosterone. Given the critical role of extracellular calcium in regulating aldosterone production, these findings warrant renewed inquiry into the validity of SST interpretations for excluding primary aldosteronism.

The Molecular Mechanisms Underlying the Systemic Effects Mediated by Parathormone in the Context of Chronic Kidney Disease

Chronic kidney disease (CKD) stands as a prominent non-communicable ailment, significantly impacting life expectancy. Physiopathology stands mainly upon the triangle represented by parathormone-Vitamin D-Fibroblast Growth Factor-23. Parathormone (PTH), the key hormone in mineral homeostasis, is one of the less easily modifiable parameters in CKD; however, it stands as a significant marker for assessing the risk of complications. The updated "trade-off hypothesis" reveals that levels of PTH spike out of the normal range as early as stage G2 CKD, advancing it as a possible determinant of systemic damage. The present review aims to review the effects exhibited by PTH on several organs while linking the molecular mechanisms to the observed actions in the context of CKD. From a diagnostic perspective, PTH is the most reliable and accessible biochemical marker in CKD, but its trend bears a higher significance on a patient's prognosis rather than the absolute value. Classically, PTH acts in a dichotomous manner on bone tissue, maintaining a balance between formation and resorption. Under the uremic conditions of advanced CKD, the altered intestinal microbiota majorly tips the balance towards bone lysis. Probiotic treatment has proven reliable in animal models, but in humans, data are limited. Regarding bone status, persistently high levels of PTH determine a reduction in mineral density and a concurrent increase in fracture risk. Pharmacological manipulation of serum PTH requires appropriate patient selection and monitoring since dangerously low levels of PTH may completely inhibit bone turnover. Moreover, the altered mineral balance extends to the cardiovascular system, promoting vascular calcifications. Lastly, the involvement of PTH in the Renin-Angiotensin-Aldosterone axis highlights the importance of opting for the appropriate pharmacological agent should hypertension develop.

Evaluating the effect of vitamin D supplementation on serum levels of 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, parathyroid hormone and renin-angiotensin-aldosterone system: a systematic review and meta-analysis of clinical trials

BACKGROUND

Vitamin D, one of the most essential micronutrients, is crucial in various health outcomes. However, previous studies showed conflicting results and uncertainty about vitamin D supplementation's optimal dosage and duration. In this study, we aimed to evaluate the vitamin D supplements efficiency on serum levels of 25-hydroxy vitamin D (25(OH)D), 1,25-dihdroxy vitamin D (1,25(OH)2D), parathyroid hormone (PTH) and renin-angiotensin-aldosterone system (RAAS) in adults.

METHODS

A systematic analysis of eligible and relevant randomized-controlled trials (RCT) published before April 2023 assessing the effect of vitamin D supplementations applied. The studies were identified by searching several databases, including Pubmed, Scopus, Web of Science, ProQuest, and Cochrane Register of controlled trials.

RESULTS

Five eligible RCTs with 346 participants in the intervention and 352 participants in the control group were assessed in our project. According to the results, there was a substantial change in 25(OH)D (SMD: 2.2, I2: 92.3, 95% Confidence Interval (CI): 1.38-3.02, P-value: 0.048) and 1,25(OH)2D (SMD:1.23, I2: 86.3, 95% CI: 0.01- 2.44, P-value < 0.010) affected by vitamin D intervention. Regarding Parathyroid hormone (PTH), however, vitamin D intervention showed a remarkable decrease (SMD: -0.75, I2: 82.4, 95% CI: (-1.3)-(-0.18), P-value < 0.010). Moreover, sensitivity analysis showed significant publication bias in terms of 25(OH)D.

CONCLUSION

Vitamin D supplements significantly increase the serum levels of 25(OH)D and 1,25(OH)2D and decrease PTH levels. While some studies reported decreasing effect of vitamin D supplements on RAAS activity, some reported no changes.

Cardiovascular and metabolic status in patients with primary hyperparathyroidism: a single-center experience

Introduction

Cardiovascular diseases (CVD) and metabolic disorders (MD) have retained leading positions in the structure of morbidity and mortality for many years. Primary hyperparathyroidism (PHPT) is also associated with a greater incidence of CVD and MD. The aim of the present study was to describe the prevalence and structure of CVD and MD in hospitalized patients with PHPT and to search for possible associations between these pathologies.

Methods

838 patients with a verified PHPT were included in the study. The studied cohort was divided into 2 groups according to their age at the time of admission: patients aged 18 to 49 years (group A, n = 150); patients aged 50 years and older (group B, n = 688).

Results

There were no significant differences between two groups in parameters of calcium-phosphorus metabolism. Obesity was diagnosed in 24.2% of patients in group A and in 35.9% in group B. Type 2 diabetes mellitus was more common in older patients (14.4% in group B vs. 2.6% in group A). Arterial hypertension, ischemic heart disease, chronic heart failure and brachiocephalic arteries atherosclerosis were more frequent in older patients, occurring in 79.1%, 10.8%, 8.4%, and 84% of cases respectively. The cutoff points that increased the risk of CVD detection turned out to be age above 56 years, eGFR below 92 ml/min/1.73m2, BMI above 28.3 kg/m2.

Discussion

The present study demonstrated a high incidence of some CVD, as well as disorders of lipid, carbohydrate and purine metabolism in patients with PHPT.

Evaluating the clinical and mechanistic effects of eplerenone and amiloride monotherapy, and combination therapy with cinacalcet, in primary hyperparathyroidism: A placebo-controlled randomized trial

OBJECTIVES

Human physiology and epidemiology studies have demonstrated complex interactions between the renin-angiotensin-aldosterone system, parathyroid hormone and calcium homeostasis. Several of these studies have suggested that aldosterone inhibition may lower parathyroid hormone (PTH) levels. The objective of this study was to assess the effect of 4 weeks of maximally tolerated mineralocorticoid receptor antagonist therapy with eplerenone on PTH levels in patients with primary hyperparathyroidism (P-HPT) when compared to amiloride and placebo. We also investigated the synergistic effect of these interventions when combined with cinacalcet for an additional 2 weeks.

DESIGN

Randomized, double-blinded, three parallel-group, placebo-controlled trial.

PATIENTS

Patients with P-HPT.

RESULTS

Most patients were women (83%) and White (76%). Maximally tolerated doses of eplerenone and amiloride induced significant reductions in blood pressure and increases in renin and aldosterone production; however, despite these physiologic changes, neither intervention induced significant changes in PTH or calcium levels when compared to the placebo. Both eplerenone and amiloride therapy induced significant reductions in procollagen type 1 N-terminal propeptide levels when compared to placebo. When cinacalcet therapy was added, PTH and calcium levels were markedly reduced in all groups; however, there was no significant difference in PTH or serum calcium reductions between groups.

CONCLUSIONS

Although maximally tolerated therapy with eplerenone and amiloride induced expected changes in renin, aldosterone and blood pressure, there were no meaningful changes in PTH or serum calcium levels in P-HPT patients. These results suggest that inhibition of aldosterone action does not have a clinically meaningful role in medical therapy for P-HPT.

Different roles of the RAAS affect bone metabolism in patients with primary aldosteronism, Gitelman syndrome and Bartter syndrome

BACKGROUND

Components of the RAAS may influence bone metabolism. Different roles of the RAAS are found in patients with primary aldosteronism (PA), Gitelman syndrome (GS) and Bartter syndrome (BS). We collected inpatient medical records including 20 patients with Gitelman syndrome (GS group), 17 patients with Bartter syndrome (BS group) and 20 age-matched patients with primary aldosteronism (PA group). We found the following results. (1) PA patients had significantly higher serum magnesium, potassium, plasma aldosterone, serum parathyroid hormone, urinary calcium and BMI (p<0.05) while significantly lower serum calcium and phosphorus (P < 0.05) than GS and BS patients. (2) Total hip and femoral neck bone mineral density (BMD) in PA patients were significantly lower than those in GS and BS patients (P<0.05). (3) GS patients had lower serum magnesium and urinary calcium than BS patients (P < 0.05). (4) Compared with BS patients, the vertebral BMD in GS patients were significantly higher (P < 0.05). So we believe higher aldosterone and PTH levels may be the reason that PA patients have lower hip BMD. Lower urinary calcium and inactivation of the NCC gene (Na-Cl cotransporter) in GS patients may have protective effects on vertebral bone mineral density.

CONCLUSIONS

With persistence disordered RAAS, PA patients have lower BMD, especially hip BMD as compared with GS and BS patients. We presumed the lower renin and higher aldosterone level may be the reason. With the same level of renin and aldosterone, BS patients have lower vertebrate BMD than GS patients. Decreased urinary calcium excretion may be the reason.

The Relationship Between Renal Stones and Primary Aldosteronism

INTRODUCTION

The association between primary aldosteronism (PA) and nephrolithiasis is still unclear. The hypercalciuria and hypocitraturia of PA patients might be the reason leading to recurrent calcium nephrolithiasis. This study aimed to evaluate the relationship between PA and renal stones, including stone size and density.

MATERIALS AND METHODS

From February 2010 to March 2021, we retrospectively collected 610 patients who presented to our medical center with hypertension history, and all these patients, suspicious of PA, had PA data survey. In total, 147 patients had kidney stone and were divided into 44 patients with essential hypertension as group 1 and 103 patients with PA as group 2. Pearson χ² test and independent Student's t-test were performed to examine the differences among variables.

RESULTS

The mean age was 54.4 ± 12.0 years in group 1 and 53.0 ± 11.1 years in group 2. The incidence rate of renal stones in the PA group was around 24%. No significant differences between the two groups were found for gender, systolic/diastolic blood pressure, duration of hypertension, diabetes mellitus history, and laterality of kidney stone; however, mean stone size was 4.0 ± 3.3 mm in group 1 and 6.5 ± 7.2 mm in group 2, with a significantly larger renal stone size noted in the PA group than that in the essential hypertension group (p = 0.004). Hounsfield unit (HU) density was higher in the PA group vis-à-vis the essential hypertension cohort, although this did not reach a significant difference (p = 0.204).

CONCLUSIONS

Our study revealed that PA patients had a higher incidence rate of renal stones compared to that of the general population. Besides, the PA-related renal stones also presented as larger and harder than those of the essential hypertension group. Further investigation concerning the association between PA and renal stones is warranted.

Impact of curative parathyroidectomy on left ventricular functions assessed with 2D ECHO and MUGA study

Objective: Primary hyperparathyroidism (PHPT) is associated with increased cardiovascular morbidity and mortality with inconsistent results on the reversibility of cardiovascular changes after parathyroidectomy (PTx). The present study was undertaken to evaluate both structural and functional cardiac changes and their reversal after PTx in patients with PHPT.

Material and Methods: Thirty patients of symptomatic PHPT without cardiovascular risk factors were evaluated prospectively by means of 2D echocar- diography (ECHO) and Multigated Acquisition (MUGA) study before surgery and six months after curative parahyroidectomy.

Results: Nine of 30 patients had hypertension which improved in two after PTx (p 0.20). Two patients had left ventricle hypertrophy on 2D ECHO pre- operatively which improved after PTx (p< 0.001). Left ventricular ejection fraction (LVEF) did not show significant change before and after PTx on 2D ECHO. Nine out of 30 patients had hypertension which improved in two after PTx (p 0.20). Two patients with left ventricle hypertrophy on 2D ECHO preoperatively improved after PTx (p< 0.001). Left ventricular ejection fraction (EF) did not depict significant change before and after PTx on 2D ECHO. Whereas, four out of six patients with preoperative EF <50% representing systolic dysfunction on MUGA study showed improvement after PTx. On 2D ECHO, eight patients depicted diastolic dysfunction which improved in six patients after curative surgery (p= 0.07). However, on MUGA study, 13 pa- tients presented with tTPF >180 ms indicating diastolic dysfunction, of which ten showed improvement after PTx (p= 0.007).

Conclusion: The present study analyzed preoperative and postoperative cardiac function using both 2D ECHO and MUGA study. MUGA study provided a more objective assessment of the cardiac function by determining left ventricular ejection fraction and diastolic dysfunction.

High-Phytate Diets Increase Amyloid β Deposition and Apoptotic Neuronal Cell Death in a Rat Model

Amyloid-β (Aβ) accumulation in the hippocampus is an essential event in the pathogenesis of Alzheimer's disease. Insoluble Aβ is formed through the sequential proteolytic hydrolysis of the Aβ precursor protein, which is cleaved by proteolytic secretases. However, the pathophysiological mechanisms of Aβ accumulation remain elusive. Here, we report that rats fed high-phytate diets showed Aβ accumulation and increased apoptotic neuronal cell death in the hippocampus through the activation of the amyloidogenic pathway in the hippocampus. Immunoblotting and immunohistochemical analyses confirmed that the overexpression of BACE1 β-secretase, a critical enzyme for Aβ generation, exacerbated the hippocampal Aβ accumulation in rats fed high-phytate diets. Moreover, we identified that parathyroid hormone, a physiological hormone responding to the phytate-mediated dysregulation of calcium and phosphate homeostasis, plays an essential role in the transcriptional activation of the Aβ precursor protein and BACE1 through the vitamin D receptor and retinoid X receptor axis. Thus, our findings suggest that phytate-mediated dysregulation of calcium and phosphate is a substantial risk factor for elevated Aβ accumulation and apoptotic neuronal cell death in rats.

Association Between Aldosterone and Parathyroid Hormone Levels in Patients With Adrenocortical Tumors

OBJECTIVE

Patients with primary aldosteronism (PA) can present with high PTH levels and negative calcium balance, with some studies speculating that aldosterone could directly stimulate PTH secretion. Either adrenalectomy or mineralocorticoid receptor blockers could reduce PTH levels in patients with PA. The aim of this study was to assess the relationship between aldosterone levels and parathyroid hormone (PTH)-vitamin D-calcium axis in a cohort of patients with PA, compared with patients with nonsecreting adrenocortical tumors in conditions of vitamin D sufficiency.

METHODS

We enrolled a series of 243 patients retrospectively, of whom 66 had PA and 177 had nonsecreting adrenal tumors, and selected those with full mineral metabolism evaluation and 25(OH) vitamin D levels >20 ng/mL at the time of initial endocrine screening. The final cohort was composed of 26 patients with PA and 39 patients, used as controls, with nonsecreting adrenal tumors. The relationships between aldosterone, PTH levels, and biochemistries of mineral metabolism were assessed.

RESULTS

Aldosterone was positively associated with PTH levels (r = 0.260, P < .05) in the whole cohort and in the PA cohort alone (r = 0.450; P = .02). In the multivariate analysis, both aldosterone concentrations and urinary calcium excretion were significantly related to PTH levels, with no effect of 25(OH) vitamin D or other parameters of bone metabolism.

CONCLUSION

PTH level is associated with aldosterone, probably independent of 25(OH) vitamin D levels and urinary calcium. Whether aldosterone interacts directly with the parathyroid glands remains to be established.

Aldosterone Secretion in Patients With Primary Hyperparathyroidism Without Arterial Hypertension

OBJECTIVE

There is a direct bidirectional link between parathyroid hormone (PTH) and the renin-angiotensin-aldosterone system (RAAS), but few studies evaluated the RAAS in patients with primary hyperparathyroidism (PHPT), mainly biased from concomitant antihypertensive treatment.

METHODS

We retrospectively evaluated a consecutive series of 130 normotensive patients with PHPT comparing aldosterone (ALD) levels and plasma renin activity (PRA) with the demographic, biochemical, or clinical features of PHPT.

RESULTS

No correlation was found between ALD and PRA, and the demographic, biochemical, and bone densitometry parameters in patients with PHPT without hypertension, with the exception of a negative correlation between age and serum PRA. Moreover, there was no significant correlation between PTH and ALD levels even in patients whose PTH level was >100 ng/L (P = .088).

CONCLUSION

In our normotensive patients with PHPT, the ALD, PRA, and aldosterone/renin ratio were not correlated to PTH and calcium levels. In addition, they were neither related to PHPT clinical presentation nor renal function, vitamin D status, bone mass loss, or the presence of comorbidities such as diabetes and obesity. Further studies are needed to clarify the complex interplay between PTH and the RAAS in the modern PHPT presentation.

Parathyroid hormone may play a role in the pathophysiology of primary hypertension

Parathyroid hormone has been related with the risk of hypertension, but the matter remains controversial. We examined the association of parathyroid hormone with central blood pressure and its determinants in 622 normotensive or never-treated hypertensive subjects aged 19-72 years without diabetes, cardiovascular or renal disease, or cardiovascular medications. The methods were whole-body impedance cardiography and analyses of pulse wave and heart rate variability. Cardiovascular function was examined in sex-specific tertiles of plasma parathyroid hormone (mean concentrations 3.0, 4.3 and 6.5 pmol/L, respectively) during head-up tilt. Explanatory factors for haemodynamics were further investigated using linear regression analyses. Mean age was 45.0 (s.d. 11.7) years, BMI 26.8 (4.4) kg/m2, seated office blood pressure 141/90 (21/12) mmHg, and 309 subjects (49.7%) were male. Only five participants had elevated plasma parathyroid hormone and calcium concentrations. Highest tertile of parathyroid hormone presented with higher supine and upright aortic diastolic blood pressure (P < 0.01) and augmentation index (P < 0.01), and higher upright systemic vascular resistance (P < 0.05) than the lowest tertile. The tertiles did not present with differences in pulse wave velocity, cardiac output, or measures of heart rate variability. In linear regression analyses, parathyroid hormone was an independent explanatory factor for aortic systolic (P = 0.005) and diastolic (P = 0.002) blood pressure, augmentation index (P = 0.002), and systemic vascular resistance (P = 0.031). To conclude, parathyroid hormone was directly related to central blood pressure, wave reflection, and systemic vascular resistance in subjects without cardiovascular comorbidities and medications. Thus, parathyroid hormone may play a role in the pathophysiology of primary hypertension.

[Dynamic changes of renin-angiotensin-aldosterone system parameters after surgery of primary hyperparathyroidism]

AIM

To study an activity of the Renin-Angiotensin-Aldosterone System (RAAS) components in patients with primary hyperparathyroidism (PHPT) before and after parathyroidectomy (PTE).

MATERIALS AND METHODS

A comparative study of patients with PHPT and control group. The first stage of the study included 56 patients with PHPT (group 1) before and on the third day after PTE. The second stage was carried out in 27 patients with remission of PHPT (group 2). All patients and healthy volunteers were tested for the main parameters of phosphorus-calcium metabolism and the RAAS parameters (plasma renin activity PRA, serum aldosterone, angiotensin II AT II).

RESULTS

Patients with active PHPT demonstrated changes in RAAS activity (lower PRA, higher AT II level) comparing to control group, that have statistical significance in group 1 (p0.001 for both parameters). There were no significant differences in aldosterone levels (p1=0.090;p2=0.140). On the third day after PTE (group 1), a decrease in aldosterone level (p=0.009) and a tendency to decrease in PRA (p=0.030) were detected. However, an increase in PRA (p=0.018), a decrease in AT II concentration (p=0.032) comparing to the initial values and their normalization were observed 12 months after surgery when permanent normal serum calcium and PTH levels had been achieved. There were controversial correlations between the parameters of phosphorus-calcium metabolism and RAAS. The influence of angiotensin-converting-enzyme inhibitors and AT II receptor blockers on phosphorus-calcium metabolism in patients with PHPT was not observed.

CONCLUSION

In patients with PHPT, there were no сlear correlations of phosphorus-calcium metabolism parameters with RAAS, however an increase of AT II concentration was noted, that can take part in a development of hypertension for this endocrinopathy. PTE can have a positive effect on AT II level.

Endocrine Causes of Hypertension

PURPOSE OF REVIEW

To discuss selected endocrine causes of hypertension and to provide practical clinical recommendations regarding the evaluation and treatment of these disorders.

RECENT FINDINGS

More than 15 endocrine disorders with varying rates of prevalence can cause hypertension. For example, primary aldosteronism may exist in up to 20% of patients with resistant hypertension. Recognition of these important secondary causes of hypertension is essential to provide contemporary targeted therapies in order to improve long-term disease outcomes. Clinicians must have a broad understanding of the prevalence, clinical presentation, and current diagnostic modalities for endocrine causes of hypertension to facilitate prompt referral, identification, and optimal management of these disorders. Endocrine causes of hypertension are multifactorial and, in some cases, widely prevalent. It is important for clinicians considering secondary causes of hypertension to be knowledgeable about the underlying pathophysiology of these disorders and to understand when additional evaluation and treatment may be needed.

Physical Activity-Dependent Regulation of Parathyroid Hormone and Calcium-Phosphorous Metabolism

Exercise perturbs homeostasis, alters the levels of circulating mediators and hormones, and increases the demand by skeletal muscles and other vital organs for energy substrates. Exercise also affects bone and mineral metabolism, particularly calcium and phosphate, both of which are essential for muscle contraction, neuromuscular signaling, biosynthesis of adenosine triphosphate (ATP), and other energy substrates. Parathyroid hormone (PTH) is involved in the regulation of calcium and phosphate homeostasis. Understanding the effects of exercise on PTH secretion is fundamental for appreciating how the body adapts to exercise. Altered PTH metabolism underlies hyperparathyroidism and hypoparathyroidism, the complications of which affect the organs involved in calcium and phosphorous metabolism (bone and kidney) and other body systems as well. Exercise affects PTH expression and secretion by altering the circulating levels of calcium and phosphate. In turn, PTH responds directly to exercise and exercise-induced myokines. Here, we review the main concepts of the regulation of PTH expression and secretion under physiological conditions, in acute and chronic exercise, and in relation to PTH-related disorders.

Association Between Plasma Intact Parathyroid Hormone Levels and the Prevalence of Atrial Fibrillation in Patients With Chronic Kidney Disease - The Fukuoka Kidney Disease Registry Study

BACKGROUND

Parathyroid hormone (PTH) has been associated with cardiovascular disorders; however, it is unknown whether plasma PTH concentrations are associated with atrial fibrillation (AF) in patients with chronic kidney disease (CKD).Methods and Results:The present cross-sectional study analyzed baseline data of 3,384 patients registered in the Fukuoka Kidney Disease Registry Study, a Japanese multicenter prospective cohort study of patients with non-dialysis-dependent CKD. The outcome was prevalence of AF, and the main risk factor was plasma intact PTH concentration. Associations between plasma intact PTH concentration quartiles (Q1-Q4, from lowest to highest) and the presence of AF were analyzed using logistic regression. In all, 185 patients had AF; 22, 34, 59, and 70 patients were in Q1, Q2, Q3, and Q4 of PTH concentrations, respectively. The prevalence of AF increased incrementally with increases in plasma intact PTH. In the logistic regression model, patients with higher plasma intact PTH concentrations (Q2-Q4) had higher adjusted odds ratios (95% confidence intervals) for the prevalence of AF relative to the reference group (Q1), namely 1.33 (0.76-2.34), 1.82 ([1.06-3.13), and 1.99 (1.08-3.64), respectively (P=0.016).

CONCLUSIONS

Higher plasma intact PTH concentrations were significantly and incrementally associated with an increased prevalence of AF in non-dialysis-dependent CKD patients.

Disentangling the Relationships Between the Renin-Angiotensin-Aldosterone System, Calcium Physiology, and Risk for Kidney Stones

CONTEXT

Complex relationships between aldosterone and calcium homeostasis have been proposed.

OBJECTIVE

To disentangle the influence of aldosterone and intravascular volume on calcium physiology.

DESIGN

Patient-oriented and epidemiology studies.

SETTING

Clinical research center and nationwide cohorts.

PARTICIPANTS/INTERVENTIONS

Patient-oriented study (n = 18): Participants were evaluated after completing a sodium-restricted (RES) diet to contract intravascular volume and after a liberalized-sodium (LIB) diet to expand intravascular volume. Cross-sectional studies (n = 3755): the association between 24h urinary sodium and calcium excretion and risk for kidney stones was assessed.

RESULTS

Patient-oriented study: compared to a RES-diet, a LIB-diet suppressed renin activity (LIB: 0.3 [0.1, 0.4] vs. RES: 3.1 [1.7, 5.3] ng/mL/h; P < 0.001) and plasma aldosterone (LIB: 2.0 [2.0, 2.7] vs. RES: 20.0 [16.1, 31.0] vs. ng/dL; P < 0.001), but increased calciuria (LIB: 238.4 ± 112.3 vs. RES: 112.9 ± 60.8 mg/24hr; P < 0.0001) and decreased serum calcium (LIB: 8.9 ± 0.3 vs. RES: 9.8 ± 0.4 mg/dL; P < 0.0001). Epidemiology study: mean urinary calcium excretion was higher with greater urinary sodium excretion. Compared to a urinary sodium excretion of < 120 mEq/day, a urinary sodium excretion of ≥220 mEq/day was associated with a higher risk for having kidney stones in women (risk ratio = 1.79 [95% confidence interval 1.05, 3.04]) and men (risk ratio = 2.06 [95% confidence interval 1.27, 3.32]).

CONCLUSIONS

High dietary sodium intake suppresses aldosterone, decreases serum calcium, and increases calciuria and the risk for developing kidney stones. Our findings help disentangle the influences of volume from aldosterone on calcium homeostasis and provide support for the recommendation to restrict dietary sodium for kidney stone prevention.

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.

Associations between primary aldosteronism and diabetes, poor bone health, and sleep apnea-what do we know so far?

Primary aldosteronism (PA), the most common cause of secondary hypertension, is a well-recognized condition that can lead to cardiovascular and renal complications. PA is frequently left undiagnosed and untreated, leading to aldosterone-specific morbidity and mortality. In this review we highlight the evidence linking PA with other conditions such as (i) diabetes mellitus, (ii) obstructive sleep apnea, and (iii) bone health, along with clinical implications and proposed underlying mechanisms.

Plasma total calcium concentration is associated with blood pressure and systemic vascular resistance in normotensive and never-treated hypertensive subjects

Purpose: The underlying causes of primary hypertension are not fully understood. Evidence on the relation of plasma calcium concentration with blood pressure (BP) is inconsistent and relies largely on studies utilizing office BP measurements in populations using cardiovascular drugs. In many studies adjustment for confounders was not optimal. In this cross-sectional study we examined the association of plasma total calcium concentration with the haemodynamic determinants of blood pressure.Subjects and methods: Supine haemodynamics were recorded using pulse wave analysis, whole-body impedance cardiography, and heart rate variability analysis in 618 normotensive or never-treated hypertensive subjects (aged 19-72 years) without diabetes, cardiovascular or renal disease, or cardiovascular medications. Linear regression analysis was used to investigate factors associated with haemodynamic variables.Results: Mean age was 45.0 years, body mass index 26.8 kg/m², seated office BP 141/89 mmHg, and 307 subjects (49.7%) were male. Mean values of routine blood and plasma chemistry analyses were within the reference limits of the tests except for low-density lipoprotein cholesterol (3.05 mmol/l). In the laboratory, mean supine radial BP was 131/75 mmHg, and both systolic and diastolic BP correlated directly with plasma total calcium concentration (r = 0.25 and r = 0.22, respectively, p < 0.001 for both). In regression analysis plasma total calcium concentration was an independent explanatory variable for radial and aortic systolic and diastolic BP, and systemic vascular resistance, but not for cardiac output, pulse wave velocity, or any of the heart rate variability parameters.Conclusion: Plasma total calcium concentration was directly associated with systolic and diastolic BP and systemic vascular resistance in normotensive or never-treated hypertensive subjects without comorbidities and cardiovascular medications. Higher plasma calcium concentration potentially plays a role in primary hypertension via an effect on vascular resistance.

Low dietary magnesium intake alters vitamin D-parathyroid hormone relationship in adults who are overweight or obese

Vitamin D metabolism is dependent on magnesium (Mg) as a cofactor; therefore, poor Mg status may alter the relationship between vitamin D metabolite serum 25-hydroxyvitamin D (s25OHD) and serum parathyroid hormone (sPTH). We hypothesized that low dietary Mg intake may alter sPTH response to s25OHD in a population with excess body weight, thereby leading to a worsening of cardiometabolic health. To explore this hypothesis, we conducted a cross-sectional study on adults who were either overweight or obese (owt/ob). Dietary Mg intake was measured using a Mg food frequency questionnaire (MgFFQ). Body composition information was measured using Dual Energy X-ray Absorptiometry (DXA). Blood samples were obtained for all biochemical analyses. A total of 57 participants, 22 to 65 years of age, with a body mass index between 25 to 45 kg/m² were divided into 3 groups, according to dietary Mg intake percentiles (Low Mg Group = <33 percentile, Medium Mg Group = 33 to 66 percentile, High Mg Group = >66 percentile). Higher s25OHD was negatively associated with lower sPTH in the High Mg Intake group (r = -0.472, P = .041), but not in other groups. A positive relationship between s25OHD and serum high-molecular weight adiponectin concentrations was observed in the High Mg Group (r = 0.532, r = 0.022), but not in other groups. Serum Interleukin-6 concentrations were negatively associated with s25OHD (r = -0.316, P = .017) for the entire study group. Based on these results, our study demonstrated that a low dietary Mg intake may alter PTH response to 25OHD.

Primary hyperparathyroidism: should surgery be performed on all patients? Current evidence and residual uncertainties

Primary hyperparathyroidism (pHPT) is the third most common endocrine disease and is characterized by hypercalcaemia and elevated or inappropriately 'normal' levels of the parathyroid hormone (PTH). The main target organs of PTH are the skeletal system and the kidneys. Before the 1970s, pHPT was a rarely detected disease associated with notable morbidity and premature mortality. Introduction of biochemical screening, allowing for a wide range of indications, has contributed to the detection of the full spectrum of the disease. A new entity with an isolated elevation of PTH, normocalcaemic HP, has emerged and is currently being explored. The highest incidence of pHPT, 3-5%, is observed amongst women, and the prevalence increases with age. The female-to-male ratio is 3-4 : 1 except in younger patients where distribution is equal and known hereditary causes account for approximately 10% of the cases. In the last few decades, it has become evident that fewer patients than previously believed are truly asymptomatic. The cause of pHPT is often a benign tumour, a parathyroid adenoma, and the only definite treatment is parathyroidectomy (PTX). No medical treatment, single or combined, can achieve a curing of pHPT. Recent data indicate that PTX, despite being proven to be cost-effective compared to conservative treatment, is underutilized, especially in elderly pHPT patients. The decision of PTX should always be based on a safe diagnosis, and the potential benefits of curative treatment should not be outweighed by the risks of surgery or anaesthesia.

Adrenocortical incidentalomas and bone: from molecular insights to clinical perspectives

Adrenal incidentalomas constitute a common clinical problem with an overall prevalence of around 2-3%, but are more common with advancing age being present in 10% of those aged 70 years. The majority of these lesions are benign adrenocortical adenomas (80%), characterized in 10-40% of the cases by autonomous cortisol hypersecretion, and in 1-10% by aldosterone hypersecretion. Several observational studies have shown that autonomous cortisol and aldosterone hypersecretion are more prevalent than expected in patients with osteopenia and osteoporosis: these patients have accelerated bone loss and an increased incidence of vertebral fractures. In contrast to glucocorticoid action, the effects of aldosterone on bone are less well understood. Recent data, demonstrating a concomitant co-secretion of glucocorticoid metabolites in patients with primary aldosteronism, could explain some of the metabolic abnormalities seen in patients with aldosterone hypersecretion. In clinical practice, patients with unexplained osteoporosis, particularly when associated with other features such as impaired glucose tolerance or hypertension, should be investigated for the possible presence of autonomous cortisol or aldosterone secretion due to an adrenal adenoma. Randomized intervention studies are needed, however, to investigate the optimum interventions for osteoporosis and other co-morbidities in these patients.

Effects of treatment with an angiotensin 2 receptor blocker and/or vitamin D3 on parathyroid hormone and aldosterone: A randomized, placebo-controlled trial

OBJECTIVE

Emerging evidence supports a positive, bidirectional and clinical relevant interaction between parathyroid hormone (PTH) and the renin-angiotensin-aldosterone-system (RAAS). A beneficial effect of the widely used RAAS inhibitors might include a PTH-lowering effect, as high PTH levels may be harmful to cardiovascular health. We aimed to investigate whether PTH levels are lowered by short-term treatment with an angiotensin 2 receptor blocker (valsartan) independently of coadministration of vitamin D3. Secondary end-points included effects on blood pressure, cardiac conduction and concentrations of renin and aldosterone.

DESIGN AND METHODS

In a double-blind placebo-controlled trial, we included 81 otherwise healthy postmenopausal women with high PTH levels (>6.9 pmol/L) and vitamin D insufficiency (25(OH)D < 50 nmol/L). Participants received 2 weeks of treatment with valsartan 80 mg/d, vitamin D3 70 μg/d, valsartan plus vitamin D3 or double placebo.

RESULTS

Valsartan treatment did not affect plasma PTH, although treatment reduced diastolic blood pressure (P = .01) and the aldosterone/renin ratio (P < .001). We found no associations between calciotropic hormones and RAAS markers. Vitamin D3 supplementation reduced PTH by 3.4% (25th, 75th -9.0 to 8.7) compared to a 7.1% increase (25th, 75th -2.4 to 30.9) in the placebo group (P = .01), but did not affect blood pressure, cardiac conduction or concentrations of renin and aldosterone.

CONCLUSIONS

Independently of vitamin D3, short-term valsartan treatment did not reduce PTH. Vitamin D3 reduced PTH but did not affect blood pressure, cardiac conduction or the RAAS. The study does not support a direct association between PTH and aldosterone or a blood pressure-lowering effect of vitamin D3.

Change in hydration indices associated with an increase in total water intake of more than 0.5 L/day, sustained over 4 weeks, in healthy young men with initial total water intake below 2 L/day

This secondary data analysis addressed gaps in knowledge about effects of chronic water intake. Longitudinal data from the Adapt Study were used to describe effects of prescribing a sustained increase in water intake relative to baseline, for 4 weeks, on multiple indices of total body water (TBW) flux, regulation, distribution, and volume in five healthy, free-living, young men, with mean total water intake initially below 2 L/day. Indices were measured weekly. Within-person fixed effect models tested for significant changes in indices over time and associations between changes in indices. Agreement between indices was described. Mixed models tested if baseline between-person differences in hydration indices modified changes in indices over time. Body water flux: The half-life of water in the body decreased significantly. Body water regulation: Serum osmolality decreased significantly. Urine anti-diuretic hormone, sodium, potassium, and osmolality decreased significantly. Plasma aldosterone and serum sodium increased significantly. Body water distribution: No significant changes were observed. Body water volume: Saliva osmolality decreased significantly. Body weight increased significantly by a mean ± SEM of 1.8% ± 0.5% from baseline over 4 weeks. Changes in indices were significantly inter-correlated. Agreement between indices changed over 4 weeks. Baseline saliva osmolality significantly modified responses to chronic water intake. The results motivate hypotheses for future studies: Chronic TBW deficit occurs in healthy individuals under daily life conditions and increases chronic disease risk; Sustained higher water intake restores TBW through gradual isotonic retention of potassium and/or sodium; Saliva osmolality is a sensitive and specific index of chronic hydration status.

The Parathyroid Gland and Heart Disease

The parathyroid glands are critical to maintaining calcium homeostasis through actions of parathyroid hormone (PTH). Recent clinical and molecular research has shown that direct and indirect actions of PTH also affect the heart and vasculature through downstream actions of G protein-coupled receptors in the myocardium and endothelial cells. Patients with disorders of the parathyroid gland have higher incidences of hypertension, arrhythmias, left ventricular hypertrophy, heart failure, and calcific disease which translate into increased cardiac morbidity and mortality. Importantly, clinical research also suggests that early treatment of parathyroid disorders through medical or surgical management may reverse cardiovascular remodeling and mitigate cardiac risk factors.

Effect of eplerenone on markers of bone turnover in patients with primary hyperparathyroidism - The randomized, placebo-controlled EPATH trial

Mineralocorticoid receptor (MR) antagonism may affect bone turnover via direct and indirect pathways involving parathyroid hormone, but randomized controlled trials are lacking. In a pre-specified analysis of the "Eplerenone in primary hyperparathyroidism" placebo-controlled, randomized trial (ISRCTN 33941607), effects of eight weeks MR-blockade with eplerenone on bone turnover markers in 97 patients with primary hyperparathyroidism were tested. Mean age was 67.5±9.5years, and 76 (78.4%) were females. In analysis of covariance with adjustment for baseline values, eplerenone had no significant effect on isoform 5b of the tartrate-resistant acid phosphatase (TRAP), beta-crosslaps, N-terminal propeptide of procollagen type 1 (P1NP), osteocalcin and bone-specific alkaline phosphatase. There was no significant cross-sectional correlation between plasma aldosterone concentration or the aldosterone-to-renin ratio and markers of bone turnover in multivariate linear regression models at baseline. These data provide first evidence from a randomized and placebo-controlled trial that short-term MR antagonism may not affect bone turnover, at least in patients with primary hyperparathyroidism.

Association of parathyroid hormone and vitamin D with untreated hypertension: Is it different in white-coat or sustained hypertension?

BACKGROUND

Previous reports about the relationship between a high parathyroid hormone (PTH) and low vitamin D levels with blood pressure in different hypertension groups are conflicting.

OBJECTIVE

We studied serum PTH and vitamin D levels in white-coat (WCHT) and sustained hypertension (SHT) patients who had not been on antihypertensive treatment. We also investigated the association between serum PTH and vitamin D levels with respect to blood pressure in SHT and WCHT patients.

METHODS

We included 52 SHT patients (54.06 ± 9.2 years, 32 newly diagnosed and 20 previously diagnosed with SHT who had not been treated with antihypertensive medication for 3 months or more), 48 WCHT patients (53.64 ± 9.5 years), and 50 normotensive (NT) healthy controls (53.44 ± 8.4 years) in our study. In addition to routine tests, PTH and vitamin D levels were measured.

RESULTS

Serum PTH levels were significantly higher in SHT patients not taking antihypertensive medications than in WCHT patients and NT controls (p = 0.004). Although PTH levels were higher in WCHT than in NT groups, the difference was not statistically significant. In SHT patients, PTH levels showed a positive correlation with office systolic (r = 0.363, p = 0.008), office diastolic (r = 0.282, p = 0.038), home systolic (r = 0.390, p = 0.004), and home diastolic blood pressures (r = 0.397, p = 0.003). Serum vitamin D levels were similar in SHT, WCHT and NT groups. Vitamin D levels were not associated with blood pressures in the entire study group. Furthermore, no significant relation was found between vitamin D and PTH levels in SHT and WCHT groups.

CONCLUSION

PTH levels are significantly higher in untreated SHT patients than WCHT patients and NT subjects. However, vitamin D levels are similar in SHT, WCHT and NT groups. There is a significant association between PTH levels and blood pressures suggesting PTH has a role in increase of blood pressure in SHT.

The Spectrum of Subclinical Primary Aldosteronism and Incident Hypertension: A Cohort Study

BACKGROUND

Primary aldosteronism is recognized as a severe form of renin-independent aldosteronism that results in excessive mineralocorticoid receptor (MR) activation.

OBJECTIVE

To investigate whether a spectrum of subclinical renin-independent aldosteronism that increases risk for hypertension exists among normotensive persons.

DESIGN

Cohort study.

SETTING

National community-based study.

PARTICIPANTS

850 untreated normotensive participants in MESA (Multi-Ethnic Study of Atherosclerosis) with measurements of serum aldosterone and plasma renin activity (PRA).

MEASUREMENTS

Longitudinal analyses investigated whether aldosterone concentrations, in the context of physiologic PRA phenotypes (suppressed, ≤0.50 µg/L per hour; indeterminate, 0.51 to 0.99 µg/L per hour; unsuppressed, ≥1.0 µg/L per hour), were associated with incident hypertension (defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or initiation of antihypertensive medications). Cross-sectional analyses investigated associations between aldosterone and MR activity, assessed via serum potassium and urinary fractional excretion of potassium.

RESULTS

A suppressed renin phenotype was associated with a higher rate of incident hypertension than other PRA phenotypes (incidence rates per 1000 person-years of follow-up: suppressed renin phenotype, 85.4 events [95% CI, 73.4 to 99.3 events]; indeterminate renin phenotype, 53.3 events [CI, 42.8 to 66.4 events]; unsuppressed renin phenotype, 54.5 events [CI, 41.8 to 71.0 events]). With renin suppression, higher aldosterone concentrations were independently associated with an increased risk for incident hypertension, whereas no association between aldosterone and hypertension was seen when renin was not suppressed. Higher aldosterone concentrations were associated with lower serum potassium and higher urinary excretion of potassium, but only when renin was suppressed.

LIMITATION

Sodium and potassium were measured several years before renin and aldosterone.

CONCLUSION

Suppression of renin and higher aldosterone concentrations in the context of this renin suppression are associated with an increased risk for hypertension and possibly also with increased MR activity. These findings suggest a clinically relevant spectrum of subclinical primary aldosteronism (renin-independent aldosteronism) in normotension.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Body Size and the Risk of Primary Hyperparathyroidism in Women: A Cohort Study

Greater body weight and fat mass have been associated with higher serum parathyroid hormone levels and a higher prevalence of primary hyperparathyroidism (P-HPTH) in women. However, prospective studies to evaluate whether greater body size associates with a higher incidence of developing P-HPTH have not been reported. We investigated whether greater body size was independently associated with a higher risk for developing P-HPTH in women. We conducted a prospective cohort study of 85,013 female participants in the Nurses' Health Study I followed for up to 26 years. Body size was measured via multiple metrics: weight, body mass index (BMI), and waist circumference (WC). Weight and BMI were assessed every 2 years from 1986 to 2012, and WC was assessed in 1986, 1996, and 2000. Detailed dietary and demographic exposures were quantified via validated biennial questionnaires. Incident cases of P-HPTH were confirmed by individual medical record review. Cox proportional hazards models were used to evaluate whether WC, weight, and BMI were independent risk factors for developing P-HPTH. Models were adjusted for demographic variables, comorbidities, medications, intakes of calcium and vitamin D, and exposure to ultraviolet light. We confirmed 491 incident cases of P-HPTH during 2,128,068 person-years of follow-up. The multivariable-adjusted relative risks for incident P-HPTH increased across quartiles of WC: Q1, ref; Q2, 1.34 (0.97, 1.86); Q3, 1.70 (1.24, 2.31); Q4, 2.27 (1.63, 3.18); p trend < 0.001. Similarly, the multivariable-adjusted risks for incident P-HPTH increased across quartiles of weight: Q1, ref; Q2, 1.23 (0.92, 1.65); Q3, 1.63 (1.24, 2.14); Q4, 1.65 (1.24, 2.19); p trend < 0.001. A similar but statistically non-significant trend was observed across quartiles of BMI (p trend = 0.07). In summary, body size may be an independent and modifiable risk factor for developing P-HPTH in women. © 2017 American Society for Bone and Mineral Research.

Angiotensin-Converting Enzyme Inhibition and Parathyroid Hormone Secretion

BACKGROUND

Prior studies suggest that renin-angiotensin-aldosterone system (RAAS) inhibitors decrease parathyroid hormone (PTH) secretion.

OBJECTIVE

To evaluate the effect of angiotensin-converting enzyme inhibitors (ACEi) on serum PTH in participants with and without primary hyperparathyroidism (P-HPT).

METHODS

An open-label, single-arm, pilot study whereby participants with and without P-HPT had PTH were evaluated before and after 1 week of maximally tolerated lisinopril therapy.

RESULTS

A total of 12 participants with, and 15 participants without, P-HPT successfully completed the protocol. Following 1 week of lisinopril, participants with P-HPT had a decrease in systolic blood pressure (SBP) (-6.4 mmHg, P < 0.01), an increase in plasma renin activity (PRA) (+1.50 ng/mL/h, P = 0.06), and a decrease in PTH (79.5 (21.6) to 70.9 (19.6) pg/mL, ∆ = -8.6 pg/mL, P = 0.049); however, serum and urine calcium did not change. In contrast, although 1 week of lisinopril significantly decreased SBP and increased PRA among participants without P-HPT, there were no changes in PTH or calcium.

CONCLUSION

In this short pilot investigation, 1 week of maximally titrated ACEi did not impact PTH in participants without P-HPT, but resulted in a modest and marginally significant reduction of PTH but not calcium, among participants with P-HPT. This trial is registered with ClinicalTrials.gov NCT01691781.

MECHANISMS IN ENDOCRINOLOGY: Kidney involvement in patients with primary hyperparathyroidism: an update on clinical and molecular aspects

Primary hyperparathyroidism (PHPT) is the third most common endocrine disease. Kidney is a target of both chronic elevated PTH and calcium in PHPT. The classic PHPT complications of symptomatic kidney stones and nephrocalcinosis have become rare and the PHPT current presentation is asymptomatic with uncertain and long-lasting progression. Nonetheless, the routine use of imaging and of biochemical determinations have revealed the frequent occurrence of asymptomatic kidney stones, hypercalciuria and reduced kidney function in asymptomatic PHPT patients. Though the pathogenesis is far from being elucidated, PHPT is associated with reduced renal function, in terms of estimated glomerular filtration rate, and related increased morbidity and mortality. In the last decade, the effort of the Kidney Disease: Improving Global Outcomes (KDIGO) panel of experts highlighted that even mild reduction of kidney function is associated with increased risk of cardiovascular disease. These considerations provided the basis for the Fourth Workshop recommendations of a more extensive diagnostic workout about kidney features and of wider criteria for parathyroid surgery including asymptomatic kidney disease. Moreover, kidney involvement in PHPT is likely to be affected by variants of genes coding the key molecules regulating the calcium and ions renal handling; these features might have clinical relevance and should be considered both during diagnostic workout and follow-up. Finally, the effects of parathyroid surgery and of medical treatment on kidney involvement of PHPT are reviewed.

Parathyroid Hormone and the Use of Diuretics and Calcium-Channel Blockers: The Multi-Ethnic Study of Atherosclerosis

Thiazide diuretic (TZ) use is associated with higher bone mineral density, whereas loop diuretic (LD) use is associated with lower bone density and incident fracture. Dihydropyridine-sensitive calcium channels are expressed on parathyroid cells and may play a role in parathyroid hormone (PTH) regulation. The potential for diuretics and calcium-channel blockers (CCBs) to modulate PTH and calcium homeostasis may represent a mechanism by which they influence skeletal outcomes. We hypothesized that the use of LD and dihydropyridine CCBs is associated with higher PTH, and TZ use is associated with lower PTH. We conducted cross-sectional analyses of participants treated for hypertension in the Multi-Ethnic Study of Atherosclerosis who did not have primary hyperparathyroidism or chronic kidney disease (n = 1888). We used adjusted regression models to evaluate the independent association between TZ, LD, and CCB medication classes and PTH. TZ use was associated with lower PTH when compared with non-TZ use (44.4 versus 46.9 pg/mL, p = 0.02), whereas the use of LD and CCBs was associated with higher PTH when compared with non-users of each medication class (LD: 60.7 versus 45.5 pg/mL, p < 0.0001; CCB: 49.5 versus. 44.4 pg/mL, p < 0.0001). Adjusted regression models confirmed independent associations between TZ use and lower PTH (β = -3.2 pg/mL, p = 0.0007), and LD or CCB use and higher PTH (LD: β = +12.0 pg/mL, p < 0.0001; CCB: +3.7 pg/mL, p < 0.0001). Among CCB users, the use of dihydropyridines was independently associated with higher PTH (β = +5.0 pg/mL, p < 0.0001), whereas non-dihydropyridine use was not (β = +0.58 pg/mL, p = 0.68). We conclude that in a large community-based cohort with normal kidney function, TZ use is associated with lower PTH, whereas LD and dihydropyridine CCB use is associated with higher PTH. These associations may provide a mechanistic explanation linking use of these medications to the development of skeletal outcomes. © 2016 American Society for Bone and Mineral Research.

Physical Activity and the Risk of Primary Hyperparathyroidism

CONTEXT

Primary hyperparathyroidism (P-HPTH) is relatively common and predominantly affects women. Prior studies have shown that physical activity (PA) can lower PTH levels.

OBJECTIVE

Our objective was to evaluate the hypothesis that lower PA is a risk factor for developing P-HPTH.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included 69 621 female participants in the Nurses' Health Study I followed for 22 years.

EXPOSURES

PA and other dietary and demographic exposures were quantified via detailed, and validated, biennial questionnaires.

OUTCOMES

Incident P-HPTH was confirmed by medical record review after initial assessment by questionnaire. Adjusted Cox proportional hazards models were used to evaluate whether PA was an independent risk factor for developing P-HPTH. We also evaluated the risk of developing P-HPTH when combining low PA (<16 metabolic equivalent hours/week) with a previously identified independent risk factor for developing P-HPTH: low calcium intake (<800 mg/day). The relation between PA and PTH levels was evaluated in 625 participants.

RESULTS

We confirmed 302 incident cases of P-HPTH during 1 474 993 person-years of follow-up. Participants in the highest quintile (Q) of PA had a 50% lower risk of developing P-HPTH: age-adjusted relative risks and 95% confidence intervals for incident P-HPTH by lowest to highest of PA were Q1 = 1.0 (reference); Q2 = 0.83 (0.60–1.15); Q3 = 0.84 (0.61–1.15); Q4 = 0.50 (0.34–0.74); Q5 = 0.50 (0.35–0.73); P for trend <.001. Extensive multivariable adjustments did not materially change these findings. The adjusted relative risk for developing P-HPTH among participants with the combination lower PA and lower calcium intake was 2.37-fold (1.60–3.51) higher than in participants with higher PA and higher calcium intake. PA was inversely correlated with serum PTH (ρ = −0.09, P = .03); the mean adjusted serum PTH in Q 2–5 of PA was lower than in Q 1 (36.3 vs 39.1 pg/mL, P = .02).

CONCLUSION

Low physical activity may be a modifiable risk factor for developing P-HPTH in women.

Parathyroid Gland Function in Primary Aldosteronism

Primary aldosteronism (PA) is the most frequent cause of secondary arterial hypertension. Beyond its effects on intravascular volume and blood pressure, PA causes metabolic alterations and a higher cardiovascular morbidity, which is reduced by PA-directed therapy. Experimental studies demonstrated that mineralocorticoid excess may also influence mineral homeostasis. A role in cardiovascular disease has also been attributed to parathyroid hormone (PTH). Increasing evidence supports a bidirectional interaction between aldosterone and PTH.Primary hyperparathyroidism is associated with arterial hypertension and an increased cardiovascular morbidity and mortality, which might be associated to higher aldosterone values; parathyreoidectomy results in lowered aldosterone and blood pressure levels. PA leads to secondary hyperparathyroidism, which is reversible by PA-directed therapy. A lower bone mineral density and a higher fracture rate were also shown to be reversible by PA-directed therapy. There is a suspicion of a bidirectional interaction between aldosterone and PTH, which might lead to a higher cardiovascular risk. There are more and more reports about coincident PA and primary hyperparathyroidism. From a pathophysiologic point of view this constellation is best characterized as tertiary hyperparathyroidism. Future aspects should further clarify the extent of these endocrine interactions and analyze the influence of this interplay on cardiovascular morbidity and mortality and bone health.

The association of circulating 25-hydroxyvitamin D concentration with peripheral arterial disease: A meta-analysis of observational studies

BACKGROUND AND AIMS

The association of vitamin D deficiency with cardiovascular disease is controversial. The present meta-analysis was performed to examine if circulating levels of 25-hydroxyvitamin D [25(OH)D] were lower in patients with peripheral artery disease (PAD) when compared to non-PAD controls.

METHODS

A comprehensive database search was conducted in Web of science, Scopus, PubMed, EMBASE and The Cochrane Library to identify observational studies reporting 25(OH)D concentrations in PAD patients and non-PAD participants. Data extraction and study quality assessments were conducted independently. A random-effects model was used to meta-analyse extracted data and generate standardized mean differences (SMDs) in circulating 25(OH)D levels between PAD patients and non-PAD controls. Subgroup analyses were conducted focussing on patients presenting with intermittent claudication (IC) and critical limb ischaemia (CLI).

RESULTS

Six case-control studies assessing 6418 individuals fulfilled the inclusion criteria. Two studies were considered to be of moderate methodological quality and four were considered to be of high quality. A meta-analysis of data from 1217 PAD patients and 5201 non-PAD participants showed that circulating 25(OH)D concentrations were lower in PAD patients compared with non-PAD participants (SMD = -0.32, 95% CI: -0.58, -0.05; P = 0.02). Subgroup analyses showed that 25(OH)D levels were significantly lower among PAD patients with CLI, but not IC, when compared to non-PAD controls (SMD = -1.29, 95% CI: -1.66, -0.91; P < 0.001 and SMD = -0.01, 95% CI: -0.15, 0.13; P=0.88, respectively).

CONCLUSIONS

This meta-analysis suggests that low levels of circulating 25(OH)D are associated with PAD presence, particularly in patients presenting with CLI. These data suggest the possibility that vitamin D insufficiency may contribute to the development of more advanced PAD although this remains to be confirmed.

Normocalcaemic, vitamin D-sufficient hyperparathyroidism - high prevalence and low morbidity in the general population: A long-term follow-up study, the WHO MONICA project, Gothenburg, Sweden

OBJECTIVE

There is limited knowledge about the natural history of normocalcaemic, vitamin D-sufficient hyperparathyroidism (nHPT). The aim was to study the prevalence of nHPT and its relation to morbidity.

DESIGN

Cross-sectional and retrospective study at the Sahlgrenska University Hospital, Gothenburg, Sweden.

SUBJECTS

A random population of 608 men and women, age 25-64 years, was studied in 1995 as part of the WHO MONICA study and reinvestigated in 2008 (n = 410, of whom 277 were vitamin D sufficient).

MEASUREMENTS

A serum intact parathyroid hormone (S-PTH) ≥60 ng/l was considered as HPT, S-calcium 2·15-2·49 mmol/l as normocalcaemia and S-25(OH)D ≥ 50 nmol/l as vitamin D sufficiency. Data on fractures, stroke and myocardial infarction were retrieved until 2013, that is a 17-year follow-up.

RESULTS

The prevalence of nHPT was 2·0% in 1995 (age 25-64) and 11·0% in 2008 (age 38-79). S-PTH was positively correlated with age and BMI. After adjustment for these variables, a high S-PTH level (≥60 ng/l) at follow-up was associated with previously low S-25(OH)D, high osteocalcin, S-PTH and both past and presently treated hypertension. No relation was seen with creatinine, cystatin C, malabsorption markers, thyroid function, glucose, insulin, lipids, calcaneal quantitative ultrasound, fractures, myocardial infarction, stroke or death at follow-up.

CONCLUSIONS

This small random population study showed that nHPT was common, 11% at follow-up. Only one individual developed mild hypercalcaemia in 13 years. Previous S-PTH was predictive of nHPT and hypertension was prevalent, but no increase in hard end-points was seen over a 17-year period.

Hypertension, Antihypertensive Medications, and Risk of Incident Primary Hyperparathyroidism

CONTEXT

Hypertension is associated with higher PTH levels, and specific antihypertensive medications may modulate PTH. Whether hypertension or the use of specific antihypertensive medications influences the risk of developing incident primary hyperparathyroidism (P-HPTH) is not known.

OBJECTIVE

The purpose of this study was to investigate whether a history of hypertension and the use of specific antihypertensive medications determine the risk for developing P-HPTH in a large prospective study.

DESIGN/PARTICIPANTS

A longitudinal prospective cohort of female nurses in the Nurses' Health Study I (n = 75 600), who did not have P-HPTH at baseline and completed a questionnaire assessment of lifetime history of P-HPTH were followed from 1986 to 2008. Most participants were white and postmenopausal.

SETTING

The study was a nationwide cohort study.

MAIN OUTCOME MEASURE

Incident P-HPTH was assessed initially via questionnaire and then was confirmed by medical record review. Cox proportional hazards models were used to adjust for potential confounders.

RESULTS

We documented 347 incident cases of P-HPTH during 1 719 416 person-years of follow-up. The age-adjusted relative risk (RR) for incident P-HPTH associated with hypertension was 1.80 (95% confidence interval [CI], 1.43-2.26), and the multivariate-adjusted RR was 1.45 (95% CI, 1.10-1.91). Among participants with a history of hypertension, the use of furosemide, when compared with the use of other antihypertensive medications, was associated with increased risk for developing P-HPTH; age-adjusted RR for incident P-HPTH was 1.79 (95% CI, 1.15-2.79) and multivariate-adjusted RR was 1.71 (95% CI, 1.08-2.71).

CONCLUSIONS

In a large longitudinal prospective cohort study of mostly older white women, a history of hypertension and use of furosemide were associated with a significantly higher risk of developing P-HPTH.

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.