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A 17-month-old black girl presented to the pediatric emergency department with sudden onset of her hands and feet "drawing up." A diagnosis of vitamin D deficiency rickets with tetany was made on a history of exclusive breast-feeding, low serum calcium, phosphorus, and 25-hydroxyvitamin D levels, and bone radiographs. Nutritional rickets should be considered in the differential diagnosis of acute hypocalcemia.

Hypothesis: The purpose of this experiment was to test the hypothesis that the changes in single muscle twitch tension (Pt) in a cosmonaut following exposure to long-duration microgravity may have been due to the sarcoplasmic reticulum, while the decrease in maximal voluntary contraction (MVC) relative to the electrically evoked maximal tetanic tension (Po) may reflect a reduction in control neural drive resulting from the voluntary muscle inactivity., Methods: The effects of 7-d "dry" water immersion were investigated in six subjects. Changes of contraction properties were studied in the triceps surae muscle., Results: After immersion, the MVC was reduced by 33.8% (p < 0.01), and the Po was reduced by 8.2% (p > 0.05). The difference between Po and MVC expressed as a percentage of Po and referred to as force deficiency, has also been calculated. The force deficiency increased by a mean of 44.1% (p < 0.01) after immersion. The decrease in Po was associated with increased maximal rate of tension development (7.2%). The twitch time-to-peak was not significantly changed, and half-relaxation time was decreased by 5.3%. However, the Pt was not significantly changed and the Pt/Po ratio was decreased by 8.7% (p < 0.01) after immersion. The muscle surface action potential presented an increase of its duration (18.8%) and a decrease of the amplitude and the total area (14.6% and 2.8%; p < 0.05-0.01, respectively)., Conclusion: The comparison of the electrical and mechanical alterations recorded during voluntary contractions, and in contractions evoked by electrical stimulation of the motor nerve, suggests that immersion not only modifies the peripheral processes associated with contraction, but also changes central and/or neural command of the contraction. At peripheral sites, it is proposed that the intracellular processes of contraction play the role in a contractile impairment recorded during immersion.

Objective: To test the authors' hypothesis of the causal mechanism(s) of postoperative tetany in patients with Graves disease., Summary Background Data: Previous studies by the authors suggested that postoperative tetany in patients with Graves disease occurs during the period of bone restoration and resulted from continuation of a calcium flux into bone concomitant with transient hypoparathyroidism induced by surgery., Patients and Methods: A prospective study was carried out to investigate sequential changes in serum levels of intact parathyroid hormone (iPTH), calcium and other electrolytes, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D (1,25(OH)2D), and bone metabolic markers in 109 consecutive patients with Graves disease who underwent subtotal thyroidectomy., Results: Preoperative serum iPTH levels negatively correlated with ionized calcium levels and positively correlated with 1,25(OH)2D or 1,25(OH)2D/25OHD. After the operation, there was a significant decline in levels of ionized calcium, magnesium, and iPTH. Serum iPTH was not detected in 15 patients after surgery. Four of these 15 patients, and 1 patient whose iPTH level was below normal, developed tetany. Preoperative serum ionized calcium levels were significantly lower, and iPTH levels were higher, in the 5 patients with tetany than in the 11 patients who did not develop tetany despite undetectable iPTH levels. The tetany group had significantly lower serum 25OHD levels and higher 1,25(OH)2D levels, and had increased 1,25(OH)2D/25OHD as an index of the renal 25OHD-1-hydroxylase activity than those in the nontetany group. These results suggest that patients with a high serum level of iPTH as a result of low serum calcium levels (secondary hyperparathyroidism) are susceptible to tetany under conditions of hypoparathyroid function after surgery., Conclusions: Postoperative tetany occurs in patients with secondary hyperparathyroidism caused by a relative deficiency in calcium and vitamin D because of their increased demand for bone restoration after preoperative medical therapy concomitant with transient hypoparathyroidism after surgery. Calcium and vitamin D supplements may be recommended before and/or after surgery for patients in whom postoperative tetany is expected to develop.

Background: The diagnostic classification of a malabsorption is often made more difficult, particularly in oligosymptomatic forms., Case Report: A female patient is presented, where the diagnosis of malabsorption syndrome was concluded because of recurring tetanias. This could be traced back to an oligosymptomatic celiac disease. Diagnostic course of action, differential diagnosis as well as further observation during therapy are discussed., Conclusion: Oligosymptomatic developments of celiac disease are common amongst adults and present a diagnostic challenge. The existence of a malabsorption should be considered, even if the momentary individual symptoms are unclarified.

The hyperventilation syndrome (HVS), characterised by multiple somatic symptoms induced by inappropriate hyperventilation, constitutes the physiopathological manifestation of a common disorder in general medicine. As a synonym of spasmophilia or tetany, it has the advantage of offering diagnostic criteria, even though the latter are still vaguely defined. But its definition allows for objective measurements: indeed, a decrease in PCO2 during a hyperventilation provoking test and an abnormally low PCO2 rate at rest can be easily quantified. Moreover, the HVS concept offers a treatment which is both structured (respiratory reeducation, psychotherapy and pharmacology) and efficient. Yet, a number of scientific uncertainties still exist. There is no general agreement regarding the criteria which should be taken into account in a hyperventilation provoking test in order to diagnose an hyperventilation syndrome; the specificity of such a test is weak and a placebo can induce as many symptoms as can a HVS. Respiratory reeducation has good results but does not necessarily have an effect on PCO2. Some therapists see in it no more than a mechanism of relaxation and a rational explanation of frightening symptoms. This has led some authors to reject the term "hyperventilation syndrome" and to prefer the expression "chronic hyperventilation of unknown origin".

The case is described of a 29-year-old man with renal failure and recurrent hyperparathyroidism who 3 weeks postparathyroidectomy developed hypocalcemic tetany because he was taking one-half the prescribed dose of calcitriol. He interpreted his symptoms as those of potassium intoxication and self-administered almost 1,500 mEq sodium bicarbonate. The increase in plasma sodium and osmolarity led to increased fluid intake, and at presentation he had an ionized calcium of 0.50 mmol/L, K 5.3 mmol/L, Na 148 mmol/L, total CO2 52.6 mmol/L, pO2 51.2 mm Hg, and pH of 7.61. He had gained 7 kg in weight. All abnormalities were corrected by dialysis, using initially a calcium-free dialyzate with extra calcium infused. The case illustrates the effect of alkalosis in reducing the amount of calcium that exists in ionized form, and it is suggested that complexing of calcium as calcium bicarbonate together with the pH change contributed to the decrease in ionized calcium. It is also an example of the hazards of treating patients who devise their own therapeutic regimens.

Background: The pathophysiological basis of spasmophilia is frequently magnesium deficiency and the therapeutic administration of magnesium salts has usually a favourable effect. However the parameters of magnesium balance are not always consistent with the results of electromyography. The objective of the present work was to test and interpret the relationship of results of these two basic diagnostic procedures indicated when spasmophilia is suspected., Methods and Results: Thirty-three subjects (9 men and 24 women) with suspected spasmophilia were examined by non-invasive electromyography, using the technique of surface electrodes. All subjects had concurrently biochemical examinations: serum calcium and ionized calcium, serum magnesium (S-mg), magnesium in erythrocytes (ery-Mg) and magnesium in the blood haemolysate (H-Mg). In 29 patients and oral magnesium loading test was made with evaluation of the urinary Mg excretion after a constant Mg load (U-Mg). Statistical evaluation of the investigated parameters of the magnesium balance revealed a highly significant relationship between ery-Mg and U-Mg and H-Mg and ery-Mg (p < 0.005). A less close relationship was found between H-Mg and S-Mg (p < 0.05). Total and ionized calcium was in all examined subjects within the range of the arbitrary normal range. The EMG finding was positive (the finding of two and more multiplets in the ischaemic and hyperventilation test resp.) in 30 instances, i.e. in 91% of the examined subjects. In 72% there was agreement of the positivity of the EMG and magnesium deficiency (i.e. reduced values of ery-Mg and U-Mg), positivity of EMG combined with normal parameters of the Mg balance was recorded in 18%. In 6.1% of the examined subjects magnesium deficiency was confirmed combined with a normal EMG finding., Conclusions: Concurrent positivity of EMG and magnesium deficiency in 72% justifies the therapeutic administration of magnesium. In patients with a normal magnesium deficiency and positive EMG another cause of spasmophilia must be taken into consideration, incl. technical errors of interpretation of EMG results. A negative EMG associated with magnesium deficiency can suggest the central form of tetany, where magnesium treatment is also unequivocally indicated.

Objective: There is little information regarding the clinical risk factors for postoperative tetany in patients with Graves' disease. We analysed the risk factors responsible for postoperative tetany by univariate and multivariate analysis in thyroidectomized patients with Graves' disease, and we discuss the mechanisms of hypocalcaemia and tetany after surgery., Patients: The subjects were 1742 consecutive patients with Graves' disease who underwent subtotal thyroidectomy between 1992 and 1994., Results: Univariate analysis of 15 possible risk factors demonstrated that 10 were significant: sex, required operation time, blood loss, preoperative serum calcium level, estimated weight of thyroid remnant, size of goitre, amount of excised thyroid tissue, serum alkaline phosphatase concentration, age at operation and TSH-binding inhibitory immunoglobin (TBII). In multivariate analysis in female patients, the risk factors were: preoperative lower serum calcium level, younger age, higher serum alkaline phosphatase concentration, larger size of goitre and higher value of TBII, in order of decreasing probability of significance., Conclusion: These results, combined with previous observations in which a significant decline in serum parathyroid hormone level was found in patients with Graves' disease who suffered postoperative tetany, suggests that postoperative tetany may occur during the period of bone restoration due to antithyroid drug therapy and be due to continuation of a calcium flux bone concomitant with transient hypoparathyroidism induced by surgery. Calcium supplements during preoperative period and/or after surgery may be appropriate for patients who are anticipated to develop postoperative tetany based on these risk factors.

Assuming that Ca+2 and Mg+2 play an important role in the cell (especially the neuronal and muscular ones) membrane excitability, this paper presents the place that the paraclinical specific investigations have in the proper diagnose of normal calcium serum level hypo-magnesium spasmophilia. A number of 52 patients presenting significant clinical spasmophilia, of age between 21 and 55 years old, from different professions and social classes, were selected for this study. Paraclinical investigations (spectrophotometry) showed a normal serum calcium level (an average of 9.22 mg%); also, a decrease of Mg+2 serum level (an average of 1.41 mg%) and normal levels for Na+ (3.04 g/l) and K+ (0.21 g/l). The electrophysiological investigations (EMG, EEG, VCN m, EKG) performed showed, on the EMG recordings, in 85% of the cases the presence of the typical spasmophilic repetitive discharges, increased when using compression ischemia and 3 minutes hyperventilation, while on the EEG recordings, most patients demonstrated the presence of diffuse or mainly frontal lobe cortical bioelectrical activity alteration, either in spontaneous conditions or after specific stimulation (3 minutes hyperventilation or SLI). The muscle bioelectrical activity was analyzed by mean of EMG recordings--a decrease of VCN m was detected on the SPE nerve (34.4 m/s) and also on the SPI nerve (34.2 m/s) The EKG recordings performed showed in 5% of the cases the presence of the ventricular repolarization disturbances (flat T waves). After receiving a proper treatment which included oral administration of calcium and magnesium gluconolactate, magnesium gluconolactate with B6 vitamin or Trimagant, there were important changes of all the studied parameters and so, as a specific therapy, we recommend the use of Mg+2 compounds, because it demonstrates a significant improvement of the clinical symptoms in spasmophilia and has no danger to precipitate in the body as Ca+2 exceeding does.

A case of 23-years old patient with tetany, sporadic vomiting and metabolic alkalosis with hypercreatinemia in laboratory investigations is presented. The exciting course was chronic ulcer disease complicated by pyloric stenosis. The painless course of a chronic disease combined with good general condition called attention.

Involvement of the duodenum in Crohn's disease is uncommon, and the pathomechanism of the associated acute pancreatitis remains controversial. We describe a case of Crohn's disease with duodenal involvement associated with hyperamylasemia and malabsorption showing a favorable response to steroid treatment.

Tetany is a rare form of presentation of adult celiac disease. We present three patients with spontaneous episodes of tetania who were finally diagnosed of celiac disease. All were women. In two of them an unexplained chronic anemia was previously detected. The origin of tetania was severe hypocalcemia and hypomagnesemia. After intravenous restoration of calcium and posterior free gluten diet with supplements, clinical and biological remission was achieved. In the presence of isolated tetania or unexplained anemia resistant to treatment an adult celiac disease must be disclosed.

A 14 weeks old infant was admitted to the intensive care unit with life-threatening hypocalcemic-hyperphosphatemic spasms. Hypocalcemia-hyperphosphatemia was found to have been caused by feeding a high phosphate/ low calcium soy milk. The daily uptake of calcium was calculated to have been 3.3-6 mmol that of phosphate 30 mmol. The parents strongly believed that soy milk formulas were equivalent to breast milk and cow's milk formulas and lived on a strictly vegetarian diet. Therapy with calcium (at an initial dose of 2.25 mmol/kg/day) and 1.25 OH vitamin D3 (Rocaltrol, 0.25 microgram/day) normalized Ca, PO4, vitamin D and parathyroid hormone levels rapidly. Vegetarian feeding had led to life-threatening hypocalcemic hyperphosphatemic spasms in the infant. We conclude that malnutrition and false nutritional beliefs have to be included as a potential cause of early hypocalcemia in infants.

The study intends to statuate the theoretical foundations concerning the etiopathogenesis (of endocrinological origin--tetany) of the myofacial pain dysfunction (MPD). We want to demonstrate this affirmation knowing that there is a very important correlation between the endocrine glands and the muscular stomatognathic activity. The EMG exam in tetany for the masticatory muscles proves that there is a repetitive asymmetric bioelectric activity even for the rest positions.

Objective: To determine the effect of transcutaneous neuromuscular electrical stimulation (TNMES) on the degree of microvascular perfusion in autonomically denervated skeletal muscle., Design: A completely randomized experimental design was used to compare the effects of TNMES on the degree of microvascular perfusion in the tibialis anterior (TA) and extensor digitorum longus (EDL) muscles from autonomically denervated rats (Ch-TES) to the degree of microvascular perfusion in the same muscles of untreated controls, rats receiving only TNMES (TES), and rats receiving only autonomic denervation (shams)., Intervention: All electrical stimulation treatments were delivered via carbon silicone surface electrodes, and evoked sustained tetanic contraction of the TA and EDL muscles. Autonomic denervation was achieved by the application of chlorisondamine., Main Outcome Measures: The degree of microvascular perfusion was determined for the deep (DTA) and superficial (STA) region of the TA muscle and the EDL muscle by calculating their perfused microvessel/muscle fiber (PV/F) ratio., Results: The PV/F ratio in the DTA from Ch-TES animals was greater (p < or = .05) than that in the same muscle from control and sham animals. The PV/F ratios in the STA and EDL from Ch-TES animals were not significantly (p > .05) different from the PV/F ratio in the respective muscles of shams., Conclusions: The response of the microvasculature in autonomically denervated skeletal muscle to TNMES that evokes muscle contraction is variable, and (2) mechanisms other than autonomic regulation may be involved in this hyperemic response.

Neuronal Hyperexcitability Syndrome (NHS) is a nosographic picture which is difficult to diagnose, due to the lack of specific standard diagnostic criteria. With slightly varying symptoms the syndrome has also been defined as Spasmophilia and Hyperventilation Syndrome. It is difficult to distinguish between NHS and panic attack disorder as there is considerable overlapping of symptomatology. We aimed to propose a standardized card which will be the first step toward a valid diagnosis of this complex neuropsychiatric problem. This card, which will be validated and of which the reliability will be evaluated, is proposed for clinical and research purposes. The card is made up of 6 parts (113 items) covering: personal data, pharmacological treatment, persistent diseases and related therapies, symptomatology trend, factors interfering with calcium-magnesium homeostasis and symptom assessment. The symptom assessment section is essential for the checking of diagnostic criteria and the earlier sections are important for the monitoring of other factors which can cause symptoms able to simulate NHS. There are also two special sections for recording laboratory tests and patients' psychic profiles.

We investigated the relationship between the progress of afterdischarges (AD) and the development of facilitated entorhinal tetanic responses by amygdala kindling stimulations in conscious and pentobarbital (PB)-treated rats. The entorhinal responses consisted of deep negative components and the following shallow positive components. The negative potential (mean +/- SE) reflecting excitatory synaptic activation in the test response evoked by a single stimulation (600 microA) before kindling stimulations was greater in PB-treated rats (1.3 +/- 0.21 mV, n = 6) than in conscious rats (0.5 +/- 0.08 mV, n = 9). The positive potential reflecting inhibitory synaptic activation in the test response was also greater in PB-treated rats (0.6 +/- 0.14 mV, n = 6) than in conscious rats (0.2 +/- 0.04 mV, n = 9). The magnitude of the tetanic response was estimated as the area between the excitatory negative potential and the baseline in the averaged tetanic response during each kindling stimulation (10 Hz, 100 pulses). The magnitude of the tetanic response was significantly enhanced in association with the prolongation of AD duration in the conscious rats. In the PB-treated (50 mg/kg intraperitoneally, i.p.) rats, enhancement of tetanic response was very slight and the progress of AD duration was prevented. There was a linear correlation (r = 0.9) between the magnitude of tetanic response and AD duration. These findings indicate that PB suppresses kindling-induced enhancement of excitatory synaptic activation in tetanic responses and that this enhancement is intimately related to the development of AD.

Magnesium is absorbed mainly from the reticulo-rumen and there are a number of factors reducing its absorption. The chief of these is the increased potential difference across the rumen epithelium caused by increased intraruminal potassium concentration. A significant amount of magnesium leaves the extracellular fluid each day as saliva. As only a portion of it is reabsorbed the rest is lost through the endogenous faecal excretion of magnesium. Thus, during impaired magnesium absorption, saliva could play an important role in the aetiology of hypomagnesaemia especially during dietary sodium depletion and the resultant increase in the potassium content of the saliva.

Mixed ruminal bacteria convert trans-aconitate to tricarballylate, a tricarboxylic acid which chelates blood divalent cations and decreases their availability (J. B. Russell and P. J. Van Soest, Appl. Environ. Microbiol. 47:155-159, 1984). Decreases in blood magnesium in turn cause a potentially fatal disease known as grass tetany. trans-Aconitate was stoichiometrically reduced to tricarballylate by Selenomonas ruminantium, a common ruminal bacterium in grass-fed ruminants (J. B. Russell, Appl. Environ. Microbiol. 49:120-126, 1985). When mixed ruminal bacteria were enriched with trans-aconitate, a trans-aconitate-oxidizing bacterium was also isolated (G. M. Cook, F. A. Rainey, G. Chen, E. Stackebrandt, and J. B. Russell, Int. J. Syst. Bacteriol. 44:576-578, 1994). The trans-aconitate-oxidizing bacterium was identified as Acidaminococcus fermentans, and it converted trans-aconitate to acetate, a nontoxic end product of ruminal fermentation. When S. ruminantium and A. fermentans were cocultured with trans-aconitate and glucose, tricarballylate never accumulated and all the trans-aconitate was converted to acetate. Continuous-culture studies (dilution rate, 0.1 h-1) likewise indicated that A. fermentans could outcompete S. ruminantium for trans-aconitate. When mixed ruminal bacteria were incubated in vitro with 10 mM trans-aconitate for 24 h, 45% of the trans-aconitate was converted to tricarballylate. Tricarballylate production decreased 50% if even small amounts of A. fermentans were added to the incubation mixes (0.01 mg of protein per mg of mixed bacterial protein). When A. fermentans (2 g of bacterial protein) was added directly to the rumen, the subsequent conversion of trans-aconitate to tricarballylate decreased 50%, but this effect did not persist for more than 18 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Objective: To report a case of hypocalcaemic tetany occurring in a child secondary to two phosphate enemas administered for faecal retention, and review the literature of phosphate enema toxicity in children., Clinical Features: A 23-month-old child with a repaired anorectal malformation and associated unilateral renal hypodysplasia presented with hypocalcaemic tetany (minimum serum calcium level, 1.11 mmol/L), hyperphosphataemia (maximum serum phosphate level, 6.06 mmol/L), hypokalaemia (minimum serum potassium level, 1.9 mmol/L) and dehydration 10 hours after the administration of two phosphate enemas for acute on chronic faecal retention. MANAGEMENT AND OUTCOME: Management consisted of parenteral rehydration, potassium supplementation, calcium gluconate, an enterally administered phosphate binder and saline bowel washouts to evacuate the remaining enema. She was discharged on day eight, with normal biochemical parameters and no neurological sequelae., Conclusion: The use of phosphate enemas in children under five years of age is associated with significant morbidity due to hyperphosphataemia, hypocalcaemia, hypokalaemia and dehydration. They should not be used in children under two years of age, and should be used only with extreme caution in children aged two to five years, especially in those with underlying bowel or renal dysfunction.

We report a case of a 54 year old woman with a history of recurrent Graves' disease, treated previously by thyroidectomy and later by radioiodine, who subsequently presented with tetany. Laboratory results revealed a profound hypocalcemia (total calcium 1.00 mmol/L; ionized calcium 0.53 mmol/L) and hyperphosphatemia (2.66 mmol/L) with low levels of parathyroid hormone. Although the patient's symptoms resolved after 5 days of treatment, hypocalcemia and elevated serum levels of bone-specific alkaline phosphatase (ALP, EC 3.1.3.1) activity and skeletal muscle isoenzyme (CK-MM) creatine kinase (EC 2.7.3.2) activity persisted to her discharge, 3 weeks later. Attention is drawn to the recognition and management of recalcification tetany due to the "Hungry (for calcium) Bone Syndrome," a biochemical and hormonal disturbance of calcium homeostasis and bone metabolism in the posttherapy thyrotoxic patient with hypoparathyroidism. This condition can be monitored by the use of calcium profile investigations, including bone-specific ALP, in addition to routine laboratory tests of thyroid function.

Neuromuscular complications, including tetany and laryngeal spasm, are recognized complications of hypocalcemia and hypomagnesemia. We present a continuous ambulatory peritoneal dialysis patient with hypomagnesemia who developed hyperphosphatemia and profound hypocalcemia after oral phosphate replacement for severe hypophosphatemia. The combination of hypocalcemia and hypomagnesemia resulted in life-threatening bilateral vocal cord paralysis. Phosphate replacement should be determined and given cautiously, particularly in patients with renal failure and concomitant electrolyte disturbances.

Involvement of endocrine organs is frequent in patients with HIV infections. We report the first case of symptomatic hypoparathyroidism in a patient in the course of HIV infection. He presented with tetany and hypocalcemia in the presence of decreased levels of parathyroid hormone, which persisted after correction of hypomagnesemia. The family history was negative and none of the autoimmune diseases associated with hypoparathyroidism was present. No local destruction by tumor or infection could be demonstrated apart from HIV infection. We propose a causal role of HIV infection in the development of hypoparathyroidism and discuss the possible mechanisms of parathyroid involvement in AIDS.

Traumatic ruptures of the triceps are very rare among tendon injuries. A unique case of hypocalcemic tetany that induced spontaneous triceps tendon avulsion with associated bilateral quadriceps tendon ruptures is reported. The current orthopaedic literature is reviewed, and a new application of an existing surgical treatment for repair of the major tendon ruptures is described.

Real hypoparathyroidism may develop after surgery of the thyroid, more rarely of the parathyroid. The idiopathic form is thought to be connected with autoimmune processes. We present the case of a female patient with acquired hypoparathyroidism after strumectomy 40 years ago. A clinical picture, not only with neurologic and dermatologic manifestations but also late organic sequelae of chronic hypocalcemia, i.e. calcification of basal ganglia, had developed impressively. Without the proof of laboratory tests diagnosis is difficult to establish at the first go in medical practice, since clinical symptoms may be few or widely scattered. Since the rate of strumectomies has dropped as a consequence of restricted indications, acquired hypoparathyroidism has become rarer. A simple long-term treatment with vitamin D and calcium relieves the patient from tetanic problems and prevents severe and irreversible late organic lesions.

Hypocalcemic crisis developed in a patient with monophasic synovial sarcoma after amputation of the right leg, followed by long-term treatment with cisplatin and doxorubicin. Laboratory data revealed severe hypomagnesemia and hypocalcemia. High normal intact parathyroid hormone (PTH), elevated mid-region PTH and undetectable osteocalcin levels had already been found before the appearance of obvious symptoms concomitantly associated with moderate hypomagnesemia and hypocalcemia. Further, both PTH levels measured by two different methods gradually decreased until the initiation of magnesium supplementation. The magnesium supplement immediately relieved the tetany, and induced striking increases in both intact and mid-region PTH levels transiently and continuous elevations of osteocalcin levels. These results suggest that magnesium depletion has dual effects on PTH secretion, from stimulation to inhibition, as hypomagnesemia progresses. Both relative hypoparathyroidism and refractoriness of bone to PTH were thought to be responsible for hypocalcemia due to hypomagnesemia.