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The Calcium Conundrum: Hypercalcemia of Unknown Etiology.

Hypercalcemia is a common clinical finding with a wide variety of clinical presentations and etiologies. The differential is broad and includes hyperparathyroidism, malignancy, medication adverse effects, endocrinopathies, and a variety of granulomatous diseases. We present the case of an 84-year-old woman with severe parathyroid hormone-independent hypercalcemia and elevated 1,25-OH Vitamin D. Non-necrotizing granulomas were identified on bone marrow biopsy. After an exhaustive workup for granulomatous disease, the patient was felt to have sarcoidosis isolated to the bone marrow and started o

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… Table 1 Comprehensive laboratory workup Lab Test | Result | Reference Range Calcium (Ca²⁺) | 15.3 mg/dL | 8.5 – 10.5 mg/dL Ionized Calcium (Ca²⁺) | 7.1 mg/dL | 4.57 – 5.43 mg/dL Parathyroid Hormone (PTH) | 6 pg/mL | 15 – 65 pg/mL PTH-Related Peptide (PTHrP) | 0.8 pmol/L | ≤ 4.2 pmol/L 25-OH Vitamin D … Figure 4 Trend in serum calcium Hypercalcemia swiftly corrected in the inpatient setting in response to therapeutic interventions. At the time of discharge, the patient was normocalcemic while on prednisone therapy. …

Calcium Transport in the Kidney and Disease Processes.

Calcium is a key ion involved in cardiac and skeletal muscle contractility, nerve function, and skeletal structure. Global calcium balance is affected by parathyroid hormone and vitamin D, and calcium is shuttled between the extracellular space and the bone matrix compartment dynamically. The kidney plays an important role in whole-body calcium balance. Abnormalities in the kidney transport proteins alter the renal excretion of calcium. Various hormonal and regulatory pathways have evolved that regulate the renal handling of calcium to maintain the serum calcium within defined limits despite d…

Calcium, mitochondria and the initiation of acute pancreatitis.

Acute pancreatitis is characterized by necrosis of its parenchymal cells and influx and activation of inflammatory cells that further promote injury and necrosis. This review is intended to discuss the central role of disorders of calcium metabolism and mitochondrial dysfunction in the mechanism of pancreatitis development. The disorders are placed in context of calcium and mitochondria in physiologic function of the pancreas. Moreover, we discuss potential therapeutics for preventing pathologic calcium signals that injure mitochondria and interventions that promote the removal of injured mito…

Calcium in the Backstage of Malaria Parasite Biology.

The calcium ion (Ca2+) is a ubiquitous second messenger involved in key biological processes in prokaryotes and eukaryotes. In Plasmodium species, Ca2+ signaling plays a central role in the parasite life cycle. It has been associated with parasite development, fertilization, locomotion, and host cell infection. Despite the lack of a canonical inositol-1,4,5-triphosphate receptor gene in the Plasmodium genome, pharmacological evidence indicates that inositol-1,4,5-triphosphate triggers Ca2+ mobilization from the endoplasmic reticulum. Other structures such as acidocalcisomes, food vacuole and m…

MicroRNAs and Calcium Signaling in Heart Disease.

In hearts, calcium (Ca2+) signaling is a crucial regulatory mechanism of muscle contraction and electrical signals that determine heart rhythm and control cell growth. Ca2+ signals must be tightly controlled for a healthy heart, and the impairment of Ca2+ handling proteins is a key hallmark of heart disease. The discovery of microRNA (miRNAs) as a new class of gene regulators has greatly expanded our understanding of the controlling module of cardiac Ca2+ cycling. Furthermore, many studies have explored the involvement of miRNAs in heart diseases. In this review, we aim to summarize cardiac Ca…

Disorders of Calcium Metabolism: Hypocalcemia and Hypercalcemia.

Calcium (Ca+2) is a divalent cation that plays a critical role in numerous body functions such as skeletal mineralization, signal transduction, nerve conduction, muscle contraction, and blood coagulation. Ca+2 metabolism is linked to magnesium (Mg+2) and phosphate metabolism. Ca+2 homeostasis is dependent on intestinal absorption, bone turnover, and renal reabsorption. The hormonal regulators of these processes are the parathyroid hormone (PTH), calcitriol {1,25-dihydroxyvitamin D [1,25(OH)2D]}, and serum ionized Ca+2. Cloning of the Ca+2-sensing receptor (CaSR) has greatly advanced the unders…

Regulation of urinary calcium excretion by vasopressin.

BACKGROUND: The antidiuretic hormone (ADH) or arginine vasopressin (AVP) regulates the body's water balance. Recently, modifications in AVP levels have been related to osteoporosis during ageing and microgravity/bed rest. Therefore the present study was devised to assess whether the absence of AVP, as in patients with central diabetes insipidus (CDI), modulates renal calcium excretion. METHODS: We retrospectively analysed data from 12 patients with CDI with measured 24-h urinary excretion levels of calcium. Data were available at the moment of the diagnosis when patients were drug-free and af…

Calcium Signaling in Liver Injury and Regeneration.

The liver fulfills central roles in metabolic control and detoxification and, as such, is continuously exposed to a plethora of insults. Importantly, the liver has a unique ability to regenerate and can completely recoup from most acute, non-iterative insults. However, multiple conditions, including viral hepatitis, non-alcoholic fatty liver disease (NAFLD), long-term alcohol abuse and chronic use of certain medications, can cause persistent injury in which the regenerative capacity eventually becomes dysfunctional, resulting in hepatic scaring and cirrhosis. Calcium is a versatile secondary m…

Discovery and Development of Calcium Channel Blockers.

In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose …

Remodeling of Calcium Entry Pathways in Cancer.

Ca(2+) entry pathways play important roles in control of many cellular functions, including long-term proliferation, migration and cell death. In recent years, it is becoming increasingly clear that, in some types of tumors, remodeling of Ca(2+) entry pathways could contribute to cancer hallmarks such as excessive proliferation, cell migration and invasion as well as resistance to cell death or survival. In this chapter we briefly review findings related to remodeling of Ca(2+) entry pathways in cancer with emphasis on the mechanisms that contribute to increased store-operated Ca(2+) entry (SO

Calcium phosphate: a substitute for aluminum adjuvants?

Calcium phosphate was used as an adjuvant in France in diphtheria, tetanus, pertussis and poliomyelitis vaccines. It was later completely substituted by alum salts in the late 80's, but it still remains as an approved adjuvant for the World Health Organization for human vaccination. Area covered: Thus, calcium phosphate is now considered as one of the substances that could replace alum salts in vaccines. The aim of this paper is to draw a review of existing data on calcium phosphate as an adjuvant in order to bring out the strengths and weaknesses for its use on a large scale. Expert commentar…

Mobility of calcium channels in the presynaptic membrane.

Unravelling principles underlying neurotransmitter release are key to understand neural signaling. Here, we describe how surface mobility of voltage-dependent calcium channels (VDCCs) modulates release probabilities (P(r)) of synaptic vesicles (SVs). Coupling distances of <10 to >100 nm have been reported for SVs and VDCCs in different synapses. Tracking individual VDCCs revealed that within hippocampal synapses, ∼60% of VDCCs are mobile while confined to presynaptic membrane compartments. Intracellular Ca(2+) chelation decreased VDCC mobility. Increasing VDCC surface populations by co-express…

A control engineering model of calcium regulation.

CONTEXT: A control engineering perspective provides a framework for representing important mechanistic details of the calcium (Ca) regulatory system efficiently. The resulting model facilitates the testing of hypotheses about mechanisms underlying the emergence of known Ca-related pathologies. OBJECTIVE: The objective of this work is to develop a comprehensive computational model that will enable quantitative understanding of plasma Ca regulation under normal and pathological conditions. DESIGN: Ca regulation is represented as an engineering control system where physiological subprocesses ar…

The structural consequences of calcium crystal deposition.

Calcium pyrophosphate dihydrate and basic calcium phosphate (BCP) crystals are the most common calcium-containing crystals associated with rheumatic disease. Clinical manifestations of calcium crystal deposition include acute or chronic inflammatory and degenerative arthritides and certain forms of periarthritis. The intra-articular presence of BCP crystals correlates with the degree of radiographic degeneration. Calcium crystal deposition contributes directly to joint degeneration. Vascular calcification is caused by the deposition of calcium hydroxyapatite crystals in the arterial intima. Th…

Calcium and vitamin D metabolism in sarcoidosis.

BACKGROUND: Sarcoidosis associated hypercalcemia (SAHC) may be secondary to excessive levels of 1,25-(OH)2 vitamin D3 produced by autonomous 1-alpha-hydroxylase activity within the granulomas.  The frequency, treatment, and consequences of hypercalcemia remain unclear. STUDY DESIGN AND METHODS: Two patient cohorts were studied.  In Cohort 1, the prevalence of hypercalcemia in 1606 sarcoidosis patients seen during a six year period was analyzed along with treatment and outcome. Cohort 2 consisted of  261 sarcoidosis patients with measured 25-(OH) vitamin D3 and 1,25-(OH) vitamin D3 levels. In

Calcium-alkali syndrome in the modern era.

The ingestion of calcium, along with alkali, results in a well-described triad of hypercalcemia, metabolic alkalosis, and renal insufficiency. Over time, the epidemiology and root cause of the syndrome have shifted, such that the disorder, originally called the milk-alkali syndrome, is now better described as the calcium-alkali syndrome. The calcium-alkali syndrome is an important cause of morbidity that may be on the rise, an unintended consequence of shifts in calcium and vitamin D intake in segments of the population. We review the pathophysiology of the calcium-alkali syndrome.

The need for calcium channels in cell proliferation.

Both increases in the basal cytosolic calcium concentration ([Ca2+]cyt) and [Ca2+]cyt transients play a major role in cell cycle progression, cell proliferation and division. Calcium influx and release from endoplasmic reticulum are the major routes involved in the variations in [Ca2+]cyt and past studies have clearly shown that calcium influx controls cell growth and proliferation in several cell types. Furthermore, various studies in the past thirty years have demonstrated that calcium channel expression levels, as well as cell specific expression, were determinant in these physiological pro…