Case Report: Severe Hypocalcemic Episodes Due to Autoimmune Enteropathy

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare monogenic disorder, associated with endocrine deficiencies and non-endocrine involvement. Gastrointestinal (GI) manifestations appear in approximately 25% of patients and are the presenting symptom in about 10% of them. Limited awareness among pediatricians of autoimmune enteropathy (AIE) caused by destruction of the gut endocrine cells in APECED patients delays diagnosis and appropriate therapy. We describe an 18-year-old female presenting at the age of 6.10 years with hypoparathyroidism, oral candidiasis and vitiligo. The clinical diagnosis of APECED was confirmed by sequencing the autoimmune regulator-encoding (AIRE) gene. Several characteristics of the disease-Hashimoto's thyroiditis, Addison's disease, diabetes mellitus type 1 and primary ovarian insufficiency-developed over the years. She had recurrent episodes of severe intractable hypocalcemia. Extensive GI investigations for possible malabsorption, including laboratory analyses, imaging and endoscopy with biopsies were unremarkable. Revision of the biopsies and chromogranin A (CgA) immunostaining demonstrated complete loss of enteroendocrine cells in the duodenum and small intestine, confirming the diagnosis of AIE. Management of hypocalcemia was challenging. Only intravenous calcitriol maintained calcium in the normal range. Between hypocalcemic episodes, the proband maintained normal calcium levels, suggesting a fluctuating disease course. Repeated intestinal biopsy revealed positive intestinal CgA immunostaining. The attribution of severe hypocalcemic episodes to AIE emphasizes the need for increased awareness of this unique presentation of APECED. The fluctuating disease course and repeated intestinal biopsy showing positive CgA immunostaining support a reversible effect of GI involvement. CgA immunostaining is indicated in patients with APECED for whom all other investigations have failed to reveal an explanation for the malabsorption.

Changes in mRNA of immune factors expressed by milk somatic cells of Holstein cows with hypocalcemia after calving

Changes in immune factors expressed by milk somatic cells from Holstein cows with hypocalcemia after calving were investigated in this study. Fourteen multiparous Holstein cows after their 3rd or 4th calving in one farm were used. The cows were divided into 2 groups: 7 cows needing treatment due to onset of hypocalcemia (hypocalcemia group; age = 5.53 ± 0.27 years, parity = 3.14 ± 0.14) and 7 cows without health problems (control group; age = 5.88 ± 0.31 years, parity = 3.57 ± 0.26). Milk samples were collected aseptically using a cannula and mRNA of immune factors expressed by milk somatic cells were analyzed. Milk samples (50 mL) were collected from the right rear mammary gland of cows before milking at day 1 and weeks 1, 2, 4, and 8 after calving. All milk samples showed a negative reaction to the California Mastitis Test. Levels of relative interleukin (IL)-6 and cathelicidin in the hypocalcemia group were lower than those in the control group in weeks 1 to 8. A significant difference in relative IL-6 levels was found in week 4 (P < 0.05). These results suggest that levels of IL-6 expressed by milk somatic cells may be affected by hypocalcemia in dairy cows.

Immune Checkpoint Inhibitor-Induced Hypoparathyroidism Associated With Calcium-Sensing Receptor-Activating Autoantibodies

CONTEXT

Whereas therapy with immune checkpoint inhibitors (ICIs), such as nivolumab, have substantially improved survival in several types of cancer, increased attention has been given to adverse immune events associated with their use, including the development of endocrine autoimmunity.

OBJECTIVES

First, to describe a patient with a 2-year history of metastatic small cell lung cancer who had been treated with nivolumab a few months before presentation with the signs and symptoms of severe hypocalcemia and hypoparathyroidism. Second, to investigate the etiology of the patient's hypoparathyroidism, including the presence of activating autoantibodies against the calcium-sensing receptor (CaSR), as humoral and cellular immune responses against the CaSR have been reported in patients with autoimmune hypoparathyroidism.

PARTICIPANTS

A 61-year-old female was admitted with persistent nausea, vomiting, epigastric pain, constipation, and generalized weakness. Laboratory analyses showed low total serum calcium, ionized calcium, and parathyroid hormone (PTH). The patient was diagnosed with severe hypocalcemia as a result of autoimmune hypoparathyroidism after testing positive for CaSR-activating autoantibodies.

INTERVENTIONS

She was treated with intravenous calcium gluconate infusions, followed by a transition to oral calcium carbonate, plus calcitriol, which normalized her serum calcium.

RESULTS

Her serum PTH remained low during her hospitalization and initial outpatient follow-up, despite adequate repletion of magnesium.

CONCLUSIONS

This case illustrates autoimmune hypoparathyroidism induced by ICI blockade. As ICIs are now used to treat many cancers, clinicians should be aware of the potential risk for hypocalcemia that may be associated with their use.

[The Analysis for Probable Reasons of Cd4+ T-Cell Activation Non-Linear Dependence on Extra Cellular Calcium Ion Concentration in Human Peripheral Blood in vitro]

The analysis for probable reasons of CD4+ T-cell activation non-linear dependence on [Ca2+]o in HPB in vitro is the general aim of current work. At the beginning we pursued the analysis of receptor-dependent (the mixture of monoclonal antibodies (mAbs) to CD3 and CD28 molecules) and receptor-independent (phorbol-myristate-acetate and ionomycin mixture) means to activate T cells in vitro with different [Ca2+]o in HPB. The key role of intracellular T-cell signaling systems in activated T cells in their non-similar sensitivity to calcium ions in the blood was shown. The analysis of differentiation next stages of CD4+ T-cell activation in vitro relatively [Ca2+]o in PHB demonstrates the key role of the earliest induction stages in non-similar sensitivity to calcium ions in CD4+ T-cell activation in vitro. According to the pursued analysis; the non-similar sensitivity of CD4+ T-cell in vitro to activation is in no-way connected with pace differences on the primary stages of activation process. The comparison of CD4+ memory T cells with their naive T-cell precursors in the cell activation process in hypocalcemia conditions was made in the separate experimental series. The 1st maximum consists in average of 85% CD4+CD45R0high CD69+ memory T cells. Naive CD4+CD45RAlowCD69+ T cells constitute the remainder 15%. The 2nd maximum almost completely consists of CD4+CD45R0+CD69+ memory T cells. The ratio between CD4+CD69+ T cell maximums depends on donor ages and represents linear dependence with R = -0.981. The most probable candidate on the role of CD4+ T cell, being capable of activation in hypocalcemia conditions, are memory T lymphocytes, being resistant to ionomycin action (I R) subset. To check this assumption the mononuclear cells and their IR-fraction were prepared from donor PB. Then the mononuclear cells and their IR-fraction were activated by mAbs mixture at different [EGTA] values. For IR-fraction, enriched with CD4+CD45RA-CD45R0+ memory T cells, slightly seen 1st maximum and drastic 2nd maximum in the "pathology" [Ca2+] region was observed. Most likely, namely, at the 2nd maximum, there is IR CD4+CD45RA-CD45R0+ memory T cell majority, having changed intracellular calcium signaling system, to be activated. Hence, the existence for CD4+ T cell activation two maximums in hypocalcemia conditions is connected with the presence of two subsets of CD4+ memory T cells, differing in their calcium-dependent intracellular signaling system, in HPB.

[Chronic hypocalcemia due to anti-calcium sensing receptor antibodies]

INTRODUCTION

Hypoparathyroidism is an entity associated with hypocalcemia, more frequently a consequence of neck surgery. An autoimmune etiology is rare and its diagnosis difficult to establish.

CLINICAL REPORT

52 year-old woman, with irrelevant past medical history and no significant familial conditions, referred because of hypocalcemia and basal ganglia calcifications, detected in the course of investigation of myalgias. Besides hypocalcemia (4.6 mg/ dL), hyperphosphatemia (8.7 mg/dL), undetectable parathyroid hormone and low urinary calcium, phosphorus and magnesium were present. Molecular analysis of CaSR gene excluded germinal mutations. Anti-calcium sensing receptor antibodies (anti-CaSR) were present. The patient is asymptomatic and normocalcemic under treatment with calcium and vitamin D.

DISCUSSION

Although rare, hypocalcemia due to anti-CaSR hypoparathyroidism must be considered in the absence of previous neck surgery, hypocalcemic drugs, familial history or phenotype suggesting a genetic disorder. Low or undetectable parathyroid hormone excludes pseudohypoparathyroidism and anti-CaSR positivity establishes the diagnosis.

Changes in leukocyte populations of cows with milk fever or displaced abomasum after calving

Most of the metabolic diseases of dairy cows occur within the first 2 wk after calving, and cows with a metabolic disease are prone to infectious diseases. Although metabolic diseases are generally recognized as a risk factor for infectious diseases owing to the associated decrease in immune function, the difference in immune status between cows with milk fever (MF) or displaced abomasum (DA) during the lactation period has not been clarified. Therefore, the peripheral blood leukocyte populations in 38 multiparous Holstein cows from 1 herd were analyzed after calving. The cows were divided into 3 groups according to health: 21 cows that remained clinically healthy throughout the experimental period (control group), 9 cows that had MF on the day of calving, and 8 cows with an onset of DA within 4 wk after calving. The T- and B-cell numbers were lowest at week 0, and they increased gradually after calving. There was no significant difference between the 3 groups in the number of each subset of leukocytes on the day of calving, but the number of CD8⁺ T-cells was significantly lower in the MF and DA groups than in the control group at week 1. The numbers of CD4⁺, CD8⁺, and WC1⁺ T-cells tended to be lower in the DA group than in control group from weeks 4 to 12, a tendency not observed in the MF group. These data suggest that when cows have DA around the time of calving, their lymphocyte numbers remain lower until 12 wk after calving.

Hypocalcaemia, alcohol drinking and viroimmune responses in ART recipients

Metabolic perturbations associated with HIV and antiretroviral therapies are widespread. Unfortunately, research has predominantly focused in cardiometabolic problems, neglecting other important areas. In fact, the immune-calcium-skeletal interface has been understudied despite its potential relevance in people living with HIV (PLWH). Using a case-control methodology, 200 PLWH receiving medical care were enrolled and stratified according to hazardous vs. non-hazardous alcohol intake (HAU vs. non-HAU) and calcium (Ca) levels by analyzing baseline data. The group was chosen to represent relatively "pure" HAU with minimal drug use and no psychiatric diagnoses. With these narrow parameters in place, we found evidence that HAU significantly increases TNF-α levels compared to Non-HAU (2.8 ± 0.6 vs. 1.9 ± 0.3 pg/ml, p = 0.05) and decreases blood Ca levels (9 ± 0.6 vs. 9.4 ± 0.5, p = 0.03). Our analyses also suggest that chronic inflammation, as indicated by increased TNF-α levels, is associated with hypocalcemia (hypoCa <8.6). Despite the limited prevalence of hypoCa, these findings are clinically significant given that hypoCA PLWH exhibited decreased CD4 (253 ± 224 vs. 417.7 ± 281, p = 0.02), B cells (147 ± 58 vs. 248 ± 151, p = 0.03) and NK cells (146.8 ± 90 vs. 229 ± 148, p = 0.008) and elevated CD8 (902.5 ± 438 vs. 699 ± 510, p = 0.09) compared to those with normal calcium. Furthermore, calcium effects on viral load were also evident with hypoCA exhibiting the highest loads (140,187 ± 111 vs. 35,622 ± 7770 HIV copies, p = 0.01). Multivariate analyses confirmed the significance of hypoCa in predicting viroimmune parameters. This paper provides the first evidence that hypoCa accounts for some of the variation in viroimmune measures in HAART recipients and suggests that hypoCa may be mediating alcohol's deleterious effects.

An acquired hypocalciuric hypercalcemia autoantibody induces allosteric transition among active human Ca-sensing receptor conformations

The seven-spanning calcium-sensing receptor (CaSR) activates multiple G proteins including Gq and Gi, and thereby activates a variety of second messengers and inhibits parathyroid hormone (PTH) secretion. However, the exact signaling mechanisms underlying the functional activity of CaSR are not yet fully understood. The heterozygous inactivation of CaSR or its inhibition by antibody blocking results in either familial hypocalciuric hypercalcemia or acquired hypocalciuric hypercalcemia (AHH), respectively. Here, we report the identification of a unique CaSR autoantibody in an AHH patient. Paradoxically, we find that this autoantibody potentiates the Ca(2+)/Gq-dependent accumulation of inositol phosphates by slightly shifting the dose dependence curve of the Ca(2+) mediated activation of phosphatidylinositol turnover to the left, whereas it inhibits the Ca(2+)/Gi-dependent phosphorylation of ERK1/2 in HEK293 cells stably expressing human CaSR. Treatment of these same cells with a calcimimetic, NPS-R-568, augments the CaSR response to Ca(2+), increasing phosphatidylinositol turnover and ERK1/2 phosphorylation, and overcoming the autoantibody effects. Our observations thus indicate that a calcium-stimulated CaSR primed by a specific autoantibody adopts a unique conformation that activates Gq but not Gi. Our findings also suggest that CaSR signaling may act via both Gq and Gi to inhibit PTH secretion. This is the first report of a disease-related autoantibody that functions as an allosteric modulator and maintains G protein-coupled receptors (GPCRs) in a unique active conformation with its agonist. We thus speculate that physiological modulators may exist that enable an agonist to specifically activate only one signaling pathway via a GPCR that activates multiple signaling pathways.

Parturition and Hypocalcemia Blunts Calcium Signals in Immune Cells of Dairy Cattle

The stress of parturition in the dairy cow is associated with increased susceptibility to infectious disease. During the periparturient period the demands for calcium are increased; these increased demands for calcium can result in subclinical or clinical hypocalcemia. Periparturient cows also experience significant immune suppression. Because intracellular calcium signaling is a key early feature in immune cell activation, we have hypothesized that the increased demand for calcium in periparturient cows may adversely affect intracellular calcium stores of immune cells. This reduction in intracellular calcium stores in immune cells could blunt intracellular calcium release following an activating stimulus, contributing to the immune suppression seen in these animals. To test this hypothesis, peripheral mononuclear cells were obtained from 27 multiparous dairy cows spanning a period of 2 wk before and 2 wk after parturition. Following activation of these cells by anti-CD3 antibodies plus secondary antibodies, intracellular calcium release from intracellular stores was measured. The intracellular calcium released in response to the activation signal declined as calcium demand for lactation became more intense and recovered as plasma calcium normalized. Intracellular calcium stores in peripheral mononuclear cells, estimated by pretreating cells with pervanadate and ionomycin, significantly decreased at parturition and returned to normal levels as the cows' blood calcium returned to normal levels. Hypocalcemia, which is common in periparturient dairy cows, is associated with decreased intracellular calcium stores in peripheral mononuclear cells. Our data suggest that this is the cause of a blunted intracellular calcium release response to an immune cell activation signal. It is concluded that intracellular Ca stores decrease in peripheral blood mononuclear cells (PBMC) before parturition and development of hypocalcemia. This suggests that systemic calcium stress precedes measurable hypocalcemia, particularly in cows that will develop milk fever. Therefore, PBMC intracellular Ca stores are a more sensitive measure of calcium stresses in transition cow. This decrease in PBMC intracellular Ca stores before parturition and the development of hypocalcemia contributes to periparturient immune suppression.

Thymoma-associated hypocalcemic crisis

A previously healthy male was diagnosed with a malignant thymoma. During the workup, he had syncope, which was due to severe unrecognized hypocalcemia. Additional workup was suggestive of parathyroid failure. In particular, there was no evidence of autoimmune parathyroid failure due to antibodies against the calcium-sensing receptor. Literature review reveals one additional thymoma case with these clinical features of chronic hypoparathyroidism of unknown cause.

Graves' Disease Coexisting with Probable Autoimmune Hypoparathyroidism

Organ-specific autoimmune endocrine disorders may present as single diseases or may occur together in polyendocrine syndromes. We present a report of 23-year-old female with Graves' disease and concurrent hypocalcemia. As she lacked other specific features of autoimmune polyendocrine syndromes, the most likely diagnosis was Graves' disease coexisting with autoimmune hypoparathyroidism.

In vitro and in vivo analysis of the immune system of vitamin D receptor knockout mice

Immune cells carry receptors for 1,25-dihydroxyvitamin D3 [1,25(OH)2D3; vitamin D receptor (VDR)] and individuals with severe vitamin D deficiency have immune abnormalities. The aim of this study was to investigate the role of vitamin D in the immune system by studying VDR-knockout (VDR-KO) mice. VDR-KO mice had the same metabolic phenotype as rachitic animals with severe hypocalcemia. Leukocytosis, lymphocyte subset composition in different immune organs, and splenocyte proliferation to several stimuli were normal, except for a lower response to anti-CD3 stimulation (simulation index [SI] of 13 +/- 4 vs. 24 +/- 9 in wild-type mice; p < 0.01). Macrophage chemotaxis was impaired (41 +/- 19% vs. 60 +/- 18% in wild-type mice; p < 0.01) but phagocytosis and killing were normal. In vivo rejection of allogeneic (31 +/- 12 days vs. 45 +/- 26 days of survival in wild-type mice, NS) or xenogeneic (10 +/- 2 days vs. 16 +/- 9 days of survival in wild-type mice, NS) islet grafts was comparable with wild-type mice. Surprisingly, VDR-KO mice were protected from low-dose streptozotocin-induced diabetes mellitus (LDSDM; 5% vs. 65% in wild-type mice; p < 0.001). Correcting hypocalcemia by use of lactose-rich or polyunsaturated fat-rich diets fully restored the immune abnormalities in vitro and the sensitivity to diabetes in vivo. On the other hand, treatment with 1,25(OH)2D3 protected wild-type mice against diabetes but did not protect normocalcemic VDR-KO mice. We conclude that immune defects observed in VDR-KO mice are an indirect consequence of VDR disruption because they can be restored by calcium homeostasis normalization. This study proves that although 1,25(OH)2D3 is a pharmacologic and probably a physiological immunomodulator, its immune function is redundant. Moreover, we confirm the essential role of calcium in the immune system.

A passive immunization technique against the teleost hypocalcemic hormone stanniocalcin provides evidence for the cholinergic control of stanniocalcin release and the conserved nature of the molecule

An in vivo bioassay based on 45Ca uptake from the ambient medium was used to test the efficacy of serum from rabbits immunized against trout stanniocalcin to passively immunize trout, tilapia, American eel, and guppy against endogenous stanniocalcin. The passive immunization was effective in all species. The fact that this procedure worked under both homologous and heterologous conditions, and in fish from different taxonomic infradivisions, is consistent with the view that the stanniocalcins in the four species examined share common antigenic determinants. The trout stanniocalcin antiserum had no effect on whole body calcium uptake (inCa2+) in stanniectomized eels, indicating that the effect of the antiserum was dependent on the presence of functional Stannius corpuscles. The technique was then used to show that the inhibitory effects that calcium loading and the injection of the cholinoreceptor agonist carbachol have on inCa2+ probably involve a catecholamine-induced release of endogenous stanniocalcin from the Stannius corpuscles.

Periparturient hypocalcemia in cows: effects on peripheral blood neutrophil and lymphocyte function

Periparturient dairy cows are quite susceptible to intramammary infections and clinical mastitis, epidemiologic evidence indicates that parturient paresis (milk fever) greatly increases the risk of mastitis, although a causal relationship has not been established. In the present experiment the effects of hypocalcemia at parturition on the immune status of dairy cows were investigated. Ten healthy, multiparous Holstein cows were fed a high Ca diet prepartum to induce hypocalcemia at parturition. Five of these cows received intramuscular parathyroid hormone (crude synthetic N-terminus 1-34) to prevent hypocalcemia at parturition. Effects of hypocalcemia on various neutrophil and lymphocyte functions were determined during the periparturient period, ranging from 6 wk prepartum to 5 wk postpartum. All cows exhibited severe loss of immune cell function in the weeks surrounding parturition. Hypocalcemia or the development of parturient paresis did not exacerbate the immune cell dysfunction. This implies that the degree of hypocalcemia observed did not have a large or irreversible influence on neutrophil and lymphocyte function in periparturient cows.

Alterations of immunoreactive somatostatin in thyroid C cells after induced hypercalcemia, hypocalcemia, and antithyroid drug treatment

In order to elucidate the functional significance of somatostatin in thyroid C cells, the alterations of immunoreactive somatostatin in the cells were investigated under various experimental conditions, i.e., hypercalcemia, hypocalcemia, and antithyroid drug treatment. Guinea pigs and rabbits, in which almost all C cells reveal the intense immunoreaction for somatostatin in addition to calcitonin, were used as experimental animals. After chronically induced hypercalcemia, somatostatin immunoreactivity conspicuously diminished coinciding with the decrease of calcitonin; somatostatin as well as calcitonin was responsive to induced hypercalcemia. After hypocalcemic tetany induced by injection of Escherichia coli L-asparaginase, C cells exhibited very intense immunoreactions for both calcitonin and somatostatin. After chronic treatment of ethylenethiourea, immunoreaction of somatostatin in C cells was the same as that of calcitonin. That is, when immunoreactivity for calcitonin remained unchanged, immunoreactivity for somatostatin was also intensive. However, when immunoreaction of calcitonin became very weak, the reaction of somatostatin was also weak. Thus, in all experimental conditions examined the alterations of immunoreactive somatostatin in C cells completely coincided with those of calcitonin. It seems likely that somatostatin in thyroid C cells exerts the synergistic effect on calcitonin action.

Hypercalcitoninemia in pancreatitis--evidence for immunochemical heterogeneity

Recently in our laboratory we have demonstrated increased immunoreactive calcitonin (iCT) levels in 4 patients with acute pancreatitis and hypocalcemia. The present study consists of 17 additional patients in whom serial determinations for (iCT) were performed. Furthermore, with the use of 2 different antisera directed against human calcitonin we present evidence for immunochemical heterogeneity of this hormone in acute pancreatitis.

Calcium metabolism in newborn infants. The interrelationship of parathyroid function and calcium, magnesium, and phosphorus metabolism in normal, "sick," and hypocalcemic newborns

Serum immunoreactive parathyroid hormone (iPTH) and plasma total calcium, ionized calcium, magnesium, and phosphorus levels were determined during the first 9 days of life in 137 normal term infants, 55 "sick" infants, and 43 hypocalcemic (Ca <7.5 mg/100 ml; Ca(++)<4.0 mg/100 ml) infants. In the cord blood, elevated levels of plasma Ca(++) and Ca were observed, while levels of serum iPTH were either undetectable or low. In normal newborns during the first 48 h of life there was a decrease in plasma Ca and Ca(++), while the serum iPTH level in most samples remained undetectable or low; after 48 h there were parallel increases in plasma Ca and Ca(++) and serum iPTH levels. Plasma Mg and P levels increased progressively after birth in normal infants. In the sick infants, plasma Ca, Ca(++) and P levels were significantly lower than in the normal newborns, while no significant differences were found in the plasma Mg levels. The general pattern of serum iPTH levels in the sick infants was similar to that observed in the normal group, though there was a tendency for the increase in serum iPTH to occur earlier and for the iPTH levels to be higher in the sick infants. In the hypocalcemic infants, plasma Mg levels were consistently lower than in the normal infants after 24 h of age, while no significant differences were found in the plasma P levels. Hyperphosphatemia was uncommon and did not appear to be a contributing factor in the pathogenesis of hypocalcemia in most infants. Most of the hypocalcemic infants, including those older than 48 h, had inappropriately low serum iPTH levels. Evidence obtained from these studies indicates that parathyroid secretion is normally low in the early new born period and impaired parathyroid function, characterized by undetectable or low serum iPTH, is present in most infants with neonatal hypocalcemia. Additional unknown factors appear to contribute to the lowering of plasma Ca in the neonatal period. The net effect of unknown plasma hypocalcemic factor(s) on the one hand and parathyroid activity on the other may account for differences in plasma Ca levels observed between normal, sick, and hypocalcemic infants. Depressed plasma Mg is frequently present in hypocalcemic infants. To what degree the hypomagnesemia reflects parathyroid insufficiency or the converse, to what degree parathyroid insufficiency and hypocalcemia are secondary to hypomagnesemia, is uncertain.