Intravenous calcitriol therapy in an early stage prevents parathyroid gland growth

Vitamin D: are all compounds equal?

Vitamin D is a pre-hormone essential for maintaining mineral homeostasis and also plays significant roles in bone, cardiovascular and renal health. Vitamin D deficiency is prevalent in the general population, and even more so in chronic kidney disease (CKD) patients, in which it contributes to the development and progression of mineral and bone disorder. The landscape of vitamin D treatment has evolved, with several analogues now available, each possessing distinct pharmacokinetic and pharmacodynamic properties, efficacies and safety profiles. This diversity allows for tailored, personalized approaches to treatment in CKD patients. This review aims to provide a comprehensive overview of vitamin D, including its natural sources and metabolism, and examines the main available pharmacological vitamin D products. Particular emphasis is placed on their application in CKD management, highlighting how these compounds can be strategically used to address both vitamin D deficiency and secondary hyperparathyroidism, while also acknowledging the ongoing debate about their impact on bone health and other clinical outcomes.

Parathyroid Nodular Hyperplasia and Responsiveness to Drug Therapy in Renal Secondary Hyperparathyroidism: An Open Question

The goal of the pharmacological therapy in secondary hyperparathyroidism (SHPT) is to reduce serum levels of parathyroid hormone and phosphorus, to correct those of calcium and vitamin D, to arrest or reverse the parathyroid hyperplasia. However, when nodular hyperplasia or an autonomous adenoma develops, surgery may be indicated. We reviewed the literature with the aim of defining if the echographic criteria predictive of unresponsiveness of SHPT to calcitriol therapy are valid also in the cinacalcet era and if drug therapy may reverse nodular hyperplasia of parathyroid gland (PTG). The responsiveness to therapy and regression of the nodular hyperplasia of PTG remains an open question in the calcimimetic era as well as the cutoff between medical and surgical therapy. Prospective studies are needed in order to clarify if an earlier use of cinacalcet in moderate SHPT might arrest the progression of parathyroid growth and stabilize SHPT.

Comparison of oral and intravenous alfacalcidol in chronic hemodialysis patients

Background

Activated vitamin D is the mainstay of treatment for secondary hyperparathyroidism (SHPT) in chronic hemodialysis patients. However, the optimal route of administration is still debated. The aim of our study was to compare efficacy of oral vs intravenous (IV) administration of alfacalcidol in hemodialysis. A secondary objective was to determine the cost-effectiveness advantage of oral administration.

Methods

Eighty-eight chronic hemodialysis patients receiving IV alfacalcidol three times a week were included in the study. All were switched to the same dose of alfacalcidol given orally three times a week during the hemodialysis session. A budget impact analysis was performed.

Results

Mean patient age was 64 years old and 43% were males. The mean alfacalcidol dose administered was 2.1 μg three times a week. After three months, serum parathormone (PTH) levels decreased from 80 to 59 pmol/L (p = 0.001) and total serum calcium levels increased from 2.34 to 2.40 mmol/L (p = 0.002). After six months, total serum calcium levels were still significantly higher. Alfacalcidol dosage was significantly decreased during study period; the mean reduction was 0.44 μg per dose. Finally, oral administration was associated with an annual cost reduction of 197 678$CAN and an annual nursing time reduction of 25 days.

Conclusion

Our findings support that switching IV to oral administration of alfacalcidol during hemodialysis sessions may lead to a similar control of SHPT with lower doses of activated vitamin D. This is a good strategy for optimizing compliance and may allow a dose reduction because of a greater efficacy to suppress PTH. Oral administration also has significant cost-effectiveness advantages.

Parathyroid enlargement at dialysis initiation in patients with chronic kidney diseases

The kidney chiefly maintains homeostasis of water, electrolytes, and other solutions. When kidney function is reduced, mineral metabolism is disrupted. Mineral and bone disorder in patients with chronic kidney disease associates with increased cardiovascular risk and mortality; however, management of chronic kidney disease-mineral and bone disorder in predialysis patients remains controversial. This study investigates the association between parathyroid enlargement at dialysis initiation and hyperparathyroidism management in dialysis patients. We enrolled 72 patients at dialysis initiation in this study. Using parathyroid sonography, we categorized patients based on presence (detected group; N = 18) or absence (undetected group; N = 54) of enlarged parathyroid glands and assessed the clinical characteristics and laboratory findings. A literature review of ultrasound evaluations of secondary hyperparathyroidism was conducted. Ultrasonography revealed enlarged parathyroid glands in 18 patients (25%). Serum intact parathyroid hormone levels were high in patients with enlarged parathyroid glands; however, of the 29 patients with intact parathyroid hormone levels <240 pg/mL, four had enlarged parathyroid glands. Eight of the 29 patients with serum phosphorus and calcium levels within the optimal range had enlarged parathyroid glands. Twenty of these 29 patients were followed up at 38 ± 17 months (at least 3 months): enlarged parathyroid glands were detected in 6. During follow-up, serum intact parathyroid hormone levels were significantly higher in the detected group compared with the undetected. In conclusion, enlarged parathyroid glands are frequently detected at dialysis initiation, potentially predicting the persistence of secondary hyperparathyroidism and the need for strict management.

Intravenous alfacalcidol once weekly pulse therapy for secondary hyperparathyroidism in hemodialysis patients

BACKGROUND

This study was carried out to assess the efficacy of intravenous administration of alfacalcidol once weekly versus thrice weekly in patients with poorly controlled secondary hyperparathyroidism.

METHODS

Thirty-six hemodialysis patients with intact parathyroid hormone (i-PTH) > 31.8 pmol/L were divided into two groups. Eighteen patients (Group 1) were given once weekly alfacalcidol for 6 months. The starting dose was 3 µg, which was increased or decreased by 1 µg per week. Eighteen patients (Group 2) were given thrice weekly alfacalcidol for 6 months. The starting dose was 1 µg, which was increased or decreased by 0.5 µg per dose. The dose was increased or decreased according to serum-corrected calcium (CCa), phosphorus (P), and i-PTH. Serum-CCa and P were measured weekly, whereas serum i-PTH and alkaline phosphatase were determined every month.

RESULTS

Intact-PTH reduced significantly (p < 0.001) from 86 ± 33.20 pmol/L to 31.04 ± 7.77 pmol/L and from 83.64 ± 32.12 pmol/L to 33.09 ± 11.37 pmol/L post-treatment in Groups 1 and 2, respectively. Fifty-six percent of the patients had i-PTH ≤ 31.8 pmol/L at the last observation. Serum alkaline phosphatase reduced significantly (p < 0.001) from 227.94 ± 129.86 IU/L to 163.17 ± 95.29 IU/L and from 285.39 ± 232.36 IU/L to 202.56 ± 165.84 IU/L post-treatment in Groups 1 and 2, respectively. There were no significant differences in serum levels of CCa, P, or their product.

CONCLUSION

Intravenous alfacalcidol thrice or once weekly is safe and effectively reduced the levels of i-PTH in hemodialysis patients.

Vitamin D effects on pregnancy and the placenta

Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.

Vitamin D effects on pregnancy and the placenta

Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.

Early intervention with intravenous or pulse oral vitamin D therapy is more effective in the treatment of secondary hyperparathyroidism

The K/DOQI clinical practice guidelines recommend vitamin D therapy should be started when the intact parathyroid hormone (iPTH) exceeds 300 pg/mL in patients with secondary hyperparathyroidism. To examine whether the effect of vitamin D therapy on mineral metabolism and parathyroid gland growth varies according to the stage of secondary hyperparathyroidism and iPTH level, 47 patients with secondary hyperparathyroidism received either intravenous or pulse oral vitamin D therapy. The patients were divided into two groups based on the iPTH level at the start of vitamin D therapy: the P(<300) group (N = 23) with iPTH <300 pg/mL; and the P(>or=300) group (N = 24) with iPTH >or=300 pg/mL. We examined serial changes in several serum mineral parameters and parathyroid gland volume and the cumulative incidence of parathyroidectomy in the first two years. Serum calcium, phosphorus, calcium-phosphorus product, and iPTH levels of the P(>or=300) group were significantly higher than those of the P(<300) group, and could not be maintained within the target ranges set by the K/DOQI guidelines. In contrast, the serum levels of phosphorus, calcium-phosphorus product, and iPTH were maintained within the target ranges and the parathyroid gland did not enlarge in the P(<300) group. The cumulative incidence of parathyroidectomy in the P(>or=300) group was significantly higher than in the P(<300) group. Early intervention with intravenous or pulse oral vitamin D therapy at serum iPTH <300 pg/mL can control serum phosphorus, calcium-phosphorus product, and PTH levels to the target ranges and slow the progression of secondary hyperparathyroidism.

Does cinacalcet improve the prognosis of dialysis patients?

Appropriate control of serum calcium (Ca) and inorganic phosphate (Pi) levels is required for better prognosis of dialysis patients. Cinacalcet is known to reduce not only serum parathyroid hormone (PTH) but also Ca and Pi levels; however, it remains unclear whether cinacalcet can ultimately improve the prognosis of such patients. In this paper, the ongoing prospective observational study (Q Cohort Study) and double-blind randomized controlled study (EVOLVE Study) are introduced. In the Q Cohort Study, cinacalcet therapy is indicated when intact PTH levels exceed 180 pg/mL, accounting for 31.3% of the study population (N = 3009). In the EVOLVE Study, the primary endpoint is the time to occurrence of composite events including all-cause mortality or nonfatal cardiovascular events. There is a related pilot study that treated patients over a 6-month period with cinacalcet. The findings showed that cinacalcet reduced serum PTH, Ca, and Pi levels and that if the patient had lower PTH levels at baseline, the dosage of vitamin D could be greatly reduced. Thus, in some patients concomitant vitamin D and cinacalcet therapy may be preferred to vitamin D alone.

Development of parathyroid gland hyperplasia without uremia: role of dietary calcium and phosphate

Background. Many experimental studies have demonstrated that parathyroid cell proliferation is induced by uremia and further aggravated by hypocalcemia, phosphorus retention and vitamin D deficiency. However, these factors may also promote parathyroid growth without uremia. In the present study, we examined the onset and progression of parathyroid hyperplasia regardless of the uremic setting, a situation that might occur soon during the early renal disease. Thus, the novelty of this work resides in the close examination of the time course for the expected changes in proliferation rates and their association with parathyroid hormone (PTH) release in normal rats under the physiological demands of a high-phosphate diet (HPD) or a low-calcium diet (LCD). Methods. We evaluated the functional response of the parathyroid glands in normal rats to different physiological demands an HPD 0.6% Ca, 1.2% P) and LCD 0.2% Ca, 0.6% P) and compared it with that of uremic rats. Furthermore, we also evaluated the time course for the reversal of high-P and low-Ca-induced parathyroid cell growth and PTH upon normalization of dietary Ca and P intake (0.6% Ca, 0.6% P). Proliferation was measured by flow cytometry and calcium receptor (CaR) and vitamin D receptor (VDR) expression were assessed by qRT-PCR. Results. The pattern in the development of parathyroid hyperplasia by the two dietary models was different. The HPD produced a stronger stimulus than the number of proliferating cells doubled after only 1 day, while the LCD required 5 days to induce an increase; the elevated calcitriol might be a mitigating factor. The increase in cell proliferation was accompanied by a transient down-regulation of VDR expression (higher in the HPD); the expression of CaR was not affected by either diet. Cell proliferation and VDR mRNA levels were restored to control values by Day 15; it is as though the gland had attained a sufficient level of hyperplasia to respond to the PTH challenge. Compared to normal rats, the response of uremic rats to the HPD showed sustained and much higher rates of PTH secretion and cell proliferation and sustained down-regulation of both VDR mRNA and CaR mRNA. Finally, the recovery from the HPD or LCD to a control diet resulted in a rapid restoration of PTH values (1 to 2 days), but the reduction in cell proliferation was delayed (3 to 5 days). Conclusions. Regardless of uremia, a physiological demand to increase the PTH secretion driven either by a high P or a low Ca intake is able to induce a different pattern of parathyroid hyperplasia, which might be aggravated by the down-regulation of VDR expression. The recovery from the HPD or LCD to a control diet results in a more rapid reduction in PTH than in cell proliferation.