Endocrinology & Internal Medicine & Nephrology & Family Medicine
Hypocalcémie | Clinique Omicron Québec
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Hypocalcemia is defined as a serum concentration of total calcium below 2.10 mmol/L (8.4 mg/dL), or ionized calcium below 1.15 mmol/L, after correction for albumin. It is one of the most frequent electrolyte disorders encountered in hospital practice, and its recognition is crucial because its manifestations - from benign paresthesia to generalized tetany and cardiac arrest - can be life-threatening. As with hypercalcemia, the total calcium measured must always be corrected for albumin before interpretation: severe hypoalbuminemia (in malnourished, cirrhotic or nephrotic patients) lowers total calcium without reducing biologically active ionized calcium - a situation referred to as pseudohypocalcemia. The two main causes are vitamin D deficiency (the most common worldwide - affecting 40-50 % of the Canadian population to varying degrees) and hypoparathyroidism (most often post-surgical, after total thyroidectomy or parathyroidectomy). The pathophysiology involves a reduction in one or more of the three sources of blood calcium: intestinal absorption (vitamin D-dependent), bone resorption (PTH-dependent), and renal tubular reabsorption (PTH-dependent). Management is based on etiological treatment, calcium supplementation (oral or IV, depending on the urgency), calcitriol (active vitamin D - 1,25-OH-vitamin D) or native vitamin D, depending on the cause, and in severe chronic hypoparathyroidism, recombinant parathyroid hormone (rhPTH 1-84 - Natpara).
Pathophysiology, etiologies and clinical picture
- Calcium metabolism and mechanisms of hypocalcemia : reminder of calcium regulation - see also Hypercalcemia sheet for full details : low ionized calcium → activation of parathyroid CaSR → secretion of PTH → renal effects (distal tubular calcium reabsorption + phosphaturia + stimulation of 1α-hydroxylase → calcitriol) + bone effects (osteoclastic resorption via RANK-L) + indirect intestinal effects (via calcitriol) → correction of calcemia; pathophysiological mechanisms of hypocalcemia: reduction of PTH (hypoparathyroidism) → simultaneous loss of renal calcium reabsorption + bone resorption + calcitriol production → profound hypocalcemia + hyperphosphatemia + relative hypercalciuria (kidney without PTH no longer reabsorbs filtered calcium filtered calcium) → vitamin D deficiency → reduced calcitriol production → reduced intestinal calcium absorption + reduced renal reabsorption + secondary elevation of PTH (compensatory secondary hyperparathyroidism) → elevated PTH + low 25-OHD low + calcitriol low + hypophosphatemia (PTH → phosphaturia) + acute respiratory alkalosis → pH increases → calcium-albumin binding increases → ionized calcium decreases abruptly → hypocalcemic tetany without true total hypocalcemia → hyperventilation + acute anxiety → ionized pseudo-hypocalcemia → resolution by bag breathing → hyperphosphatemia (CKD + hypoparathyroidism) → forms calcium-phosphate complexes → precipitation → reduction of ionized calcium ; calcium correction for albumin (formula identical to hypercalcemia): corrected calcium = measured calcium + 0.02 × (40 - albumin g/L) → if albuminemia = 20 g/L + measured calcium = 2.0 mmol/L → corrected calcium = 2.0 + 0.02 × 20 = 2.40 mmol/L → true normocalcemia (pseudo-hypocalcemia) → ionized calcium remains the reference in case of doubt → alkalosis → increases albumin-calcium binding → low ionized calcium despite normal total calcium → acidosis → the reverse → always interpret taking pH into account ; hungry bone syndrome: after parathyroidectomy for severe HPP or thyroid surgery with parathyroid involvement → sudden influx of calcium + phosphorus to bone (rapid remineralization post-PTH) → profound and prolonged hypocalcemia + hypophosphatemia + hypomagnesemia → Witteveen 2013 - Journal of Bone and Mineral Research: predictive factors for hungry bone syndrome: severe PPH + very high alkaline phosphatases + radiological bone LVH → massive IV calcium supplementation required + calcitriol + magnesium
- Etiologies of hypocalcemia - classification by mechanism : PTH deficiency - hypoparathyroidism: post-surgical (most frequent cause): total thyroidectomy + total parathyroidectomy + cervical lymph node emptying → involuntary lesion or removal of parathyroids → hypocalcemia in the 24-72h post-operatively → transient (6 months) in 30-40 % of cases → definitive in 1-3 % of total thyroidectomies → risk factors: bulky goiter surgery + re-operative thyroidectomy + extensive oncological surgery → autoimmune: anti-parathyroid antibodies + isolated or associated with APS-1 syndrome (autoimmune polyendocrinopathy type 1 - AIRE - hypoparathyroidism + adrenal insufficiency + mucocutaneous candidiasis) → genetic: DiGeorge syndrome (22q11 deletion.2 - thymic aplasia + congenital heart disease + hypoparathyroidism) + CaSR activating mutation (CaSR hyperactivity → constitutive PTH brake → hypocalcemia + hypercalciuria → Pollak 1994 - Nature Genetics) + PTH gene mutation + GNA11 mutation → parathyroid infiltration: hemochromatosis + granulomatoses + metastases + amyloid deposits → low magnesium (<0.5 mmol/L) → PTH resistance + reduced PTH secretion → hypomagnesemia = frequent, correctable cause of functional hypoparathyroidism → correct before any other measures + cervical irradiation + Riedel surgery; PTH resistance - pseudohypoparathyroidism (PHP): elevated PTH + hypocalcemia + hyperphosphatemia → renal resistance to PTH by mutation of GNAS gene (Gsα protein) → PHP type 1a (Albright hereditary osteodystrophy - OHA): round facies + short stature + brachydactyly + obesity + mental retardation + subcutaneous ossifications + PHP type 1b: isolated renal resistance without OHA phenotype + PHP type 2: rare → workup: elevated PTH + low calcium + elevated phosphorus + urinary cAMP not increased after PTH injection → Mantovani 2011 - Endocrine Reviews: classification and management of PHP; vitamin D deficiency and vitamin D metabolism disorders: vitamin D deficiency (low 25-OHD): most frequent cause of mild to moderate hypocalcemia in the general population → inadequate dietary intake + insufficient sun exposure (northern latitude + covering clothing + photophobia) + malabsorption (celiac disease + Crohn's + intestinal resection + bariatric surgery) + liver failure (25-hydroxylation defect) → chronic renal failure (1α-hydroxylation) + vitamin-dependent rickets type 1 (VDDR1 - mutation of 1α-hydroxylase - CYP27B1) → very low calcitriol despite normal 25-OHD + vitamin-dependent rickets type 2 (VDDR2 - mutation of VDR - vitamin D receptor) → calcitriol resistance → very high calcitriol + clinical rickets → drugs inhibiting vitamin D metabolism : rifampicin + phenytoin + phenobarbital + carbamazepine (hepatic enzyme inducers → accelerated catabolism of 25-OHD); other causes to consider: chelation of blood calcium: acute pancreatitis (saponification of peripancreatic fats by free fatty acids → insoluble calcium-fatty acid complexes) + massive transfusions (citrate → chelates ionized calcium) + IV bisphosphonates + denosumab (after treatment of hypercalcemia) + excessive IV phosphate + acute fluorosis → severe hyperphosphatemia (CKD stage V) → calcium-phosphate precipitation → reduction of ionized calcium → tumor lysis syndrome: phosphorus + uric acid + potassium massively released → hyperphosphatemia → hypocalcemia → acute renal failure + severe hypoproteinemia: pseudo-hypocalcemia (low total calcuim + normal ionized calcium) → acute respiratory alkalosis (tetany without true total hypocalcemia + common in panic attacks)
- Clinical manifestations of hypocalcemia - «the 4 Es»: symptoms depend on ionized calcium level AND speed of onset - moderate chronic hypocalcemia may be asymptomatic, whereas an acute fall in calcium (post-surgery or tumor lysis) is much more symptomatic at the same blood calcium level; neuromuscular excitability (central manifestation): perioral paresthesias + tingling of extremities (fingers + toes) → muscle cramps → overt tetany: involuntary, painful contraction of hand muscles (midwife's hand - metacarpophalangeal flexion + interphalangeal extension) + feet (ballet foot - forced plantar extension) → laryngeal tetany (stridor + dyspnea + risk of asphyxia) → generalized tetany → convulsions (hypocalcemic epilepsy - grand mal + focal + absences); provoked clinical signs (sought on physical examination): Trousseau's sign: inflation of blood pressure cuff above PAS × 3 min → ischemia → midwife's hand → sensitivity 94 % + specificity 99 % for hypocalcemia (Tohme 1993 - Annals of Internal Medicine) → Chvostek's sign: percussion of facial nerve in front of tragus → ipsilateral contraction of facial muscles (lip + nostrils) → sensitivity 25-65 % (not very specific - 10-29 % false positives in normocalcemic general population) → Lust sign: percussion of peroneal nerve → dorsiflexion + eversion of foot; cardiovascular effects: QT interval prolongation (hypocalcemia → prolongation of ventricular repolarization) → opposite of hypercalcemia → risk of ventricular arrhythmias (torsades de pointes + VF) + heart failure (chronic hypocalcemic cardiomyopathy - reversible if calcium corrected) + arterial hypotension + AV block → ECG is mandatory if symptomatic or severe hypocalcemia; psychiatric and cognitive effects: anxiety + irritability + depression + confusion + memory disorders + dementia (untreated severe chronic hypocalcaemia) + calcifications of basal ganglia (basal ganglia) in chronic hypoparathyroidism (Fahr's syndrome - chorea + parkinsonism + dementia + epilepsy); ectodermal effects (long-term chronic hypoparathyroidism): posterior subcapsular cataract + skin dryness + brittle nails + hair loss + tooth enamel dysplasia (if deficient in childhood)
Biological diagnosis and management
| Aspect / intervention | Data, criteria and procedures | Key studies and recommendations |
|---|---|---|
| Diagnostic etiology PTH - 25-OHD - magnesium - phosphorus - calcitriol - cAMP - genetics - imaging |
Diagnostic algorithm - first step: correct calcium for albumin + assay ionized calcium if in doubt → exclude pseudo-hypocalcemia (hypoalbuminemia + alkalosis); 1st-line workup in the face of confirmed true hypocalcemia: intact PTH - key to etiological diagnosis: low or inadequately normal PTH (65 pg/mL) → non-parathyroid mechanism (vitamin D + PTH resistance + chelation + other) + phosphorus: high in hypoparathyroidism and CKD + low in vitamin D deficiency (high PTH → phosphaturia) + serum magnesium: mandatory → hypomagnesemia (<0.5 mmol/L) → functional hypoparathyroidism → magnesium correction → PTH correction → 25-OH-vitamin D (25-OHD): low (<25 nmol/L = severe deficiency + 25-50 nmol/L = insufficiency) → vitamin D deficiency → calcitriol (1,25-OH-vitamin D): low despite high PTH → 1α-hydroxylation deficiency (CKD + rickets type 1 CYP27B1) → high with low PTH and normal 25-OHD → rare (rickets type 2 or autonomous production) + creatinine + GFR → CKD (1α-hydroxylase defect + hyperphosphatemia) + alkaline phosphatases: very high → increased bone turnover → rickets + severe secondary hyperparathyroidism + 24h calciuria (or urinary Ca/Creat spot) → hypercalciuria in CaSR activating mutations + treated hypoparathyroidism (risk of nephro-calcinosis if supplementation too intensive) + CBC + ESR + CRP (sarcoidosis + hemochromatosis) + liver work-up (liver failure + metastases) + systematic ECG (prolonged QT - IV treatment threshold) ; 2nd-line work-up according to orientation: anti-parathyroid antibodies (autoimmune hypoparathyroidism) + genetics: GNAS (PHP) + CaSR activator (Pollak 1994 - Nature Genetics) + AIRE (APS-1) + GNA11 + CYP27B1 (VDDR1) + VDR (VDDR2) + 22q11.2 (DiGeorge - FISH or CGH-array) + parathyroid scintigraphy + cervical CT (if suspicion of remaining nonpalpated functional ectopic parathyroids) + ferritin + transferrin saturation (hemochromatosis) + abdominal CT if sarcoidosis suspected + Ellsworth-Howard test (PTH injection → urinary cAMP not increased in PHPs) → today replaced by GNAS genetics + ophthalmological workup: fundus + slit lamp → posterior subcapsular cataract (chronic hypoparathyroidism) + brain scan if neurological symptoms: calcifications of basal ganglia (Fahr syndrome) → in untreated or inadequately treated hypoparathyroidism → no MRI (calcifications are not visible on MRI but on CT); classification of hypocalcemia severity: mild : corrected calcium 1.90-2.10 mmol/L → often asymptomatic → oral treatment + follow-up → moderate: corrected calcium 1.75-1.90 mmol/L → paresthesias + cramps → intensified oral treatment → severe: <1.75 mmol/L or severe symptoms (tetany + convulsions + prolonged QTc + arrhythmia) → emergency → IV calcium | Interpretation of the biological profile according to etiology: hypoparathyroidism: Ca↓ + PTH↓ or inadequate + PO₄↑ + normal/low Mg + normal 25-OHD + calcitriol ↓ + high calciuria → vitamin D deficiency: Ca↓ slightly + PTH↑ + PO₄↓ + 25-OHD↓↓ + variable calcitriol + PAL↑ + calciuria↓ → CKD: Ca↓ + PTH↑↑ (secondary) + PO₄↑ + 25-OHD↓ + calcitriol↓ + creatinine↑ → PHP: Ca↓ + PTH↑↑ + PO₄↑ + normal 25-OHD + calcitriol↓ + non-stimulable urinary cAMP → activating CaSR mutation: Ca↓ + maladaptive (low) PTH + normal calciuria↑↑ + PO₄ → Bilezikian 2016 - Journal of Bone and Mineral Research : international guidelines for hypoparathyroidism → consensus of 73 experts → therapeutic targets + indications for recombinant PTH + Mannstadt 2017 - Nature Reviews Disease Primers: comprehensive review of hypoparathyroidism → epidemiology + mechanisms + treatment |
| Treatment of acute hypocalcemia and tetany IV calcium gluconate - calcium chloride - continuous infusion - calcitriol - magnesium - ECG monitoring |
Treatment of acute or severe symptomatic hypocalcemia (calcium <1.75 mmol/L or neuromuscular signs): intravenous calcium - emergency treatment: calcium gluconate 10 % (standard solution): 1-2 ampoules of 10 mL (each containing 93 mg = 2.3 mmol elemental calcium) → dilute in 50-100 mL saline or G5 % → infuse in 10-20 min → never inject as a direct bolus (risk of severe bradycardia + asystole) → effect on QT in 15-30 min → peripheral or central route (calcium gluconate is less irritating than calcium chloride → peripheral IV preferred) → calcium chloride 10 %: contains 3 times more elemental calcium (272 mg / 10 mL) → reserved for central venous access or extreme emergencies → very irritating to peripheral veins → risk of necrosis if extravasated → maintenance infusion if persistent profound hypocalcemia: calcium gluconate 10 %: 8-12 ampoules in 1 L saline → flow rate: 50-100 mL/h → adjust according to ionized calcemia (target 1.15-1.25 mmol/L) → monitor calcemia every 2-4h + continuous ECG + diuresis → extravasation of IV calcium: risk of skin necrosis → use central line or large vein → do not mix calcium with bicarbonate (precipitation); magnesium correction if hypoMg: magnesium sulfate 1-2 g IV over 10-15 min + infusion maintenance → essential before PTH can respond normally → without magnesium correction → calcium supplementation will be insufficient → systematically check magnesium in any hypocalcemia; emergency calcitriol initiation (suspected hypoparathyroidism): calcitriol (Rocaltrol) 0.25-0.5 µg 2×/d orally → rapid onset of action (12-24h for onset of intestinal effect) → essential in hypoparathyroidism (absence of endogenous renal calcitriol production under PTH) → do not wait for full correction to initiate → objectives: corrected calcium maintained between 2.00 and 2.25 mmol/L (do not aim for full normality → risk of nephro-calcinosis and lithiasis if Ca × PO₄ high) → monitor calciuria (target <7.5 mmol/24h); treatment of true hypocalcemic tetany as an emergency: IV calcium according to above scheme + continuous ECG monitoring + reassure patient + treat triggering cause + if laryngeal tetany: intubation if severe stridor + emergency call + immediate IV calcium gluconate; pseudo-tetany by hyperventilation (acute respiratory alkalosis): bag breathing (rebreathing CO₂) → correction of alkalosis → ionized calcium normalizes → no IV calcium → anxiolytic if panic attack + treatment of underlying anxiety | Data on IV treatment of acute hypocalcemia: Cooper 2012 - New England Journal of Medicine (review): calcium gluconate IV = gold standard treatment of acute symptomatic hypocalcemia → 1-2 g IV in 10-20 min → followed by maintenance infusion if persistent ionized calcium 500 ms + ionized calcium <1.0 mmol/L → immediate IV treatment → correction → QTc shortens in 15-30 min → Zaloga 1992 - Critical Care Medicine: hypocalcemia in intensive care → frequency 15-20 % of ICU patients + poor prognostic factor + Moe 2008 - Kidney International: treatment of hypocalcemia in CKD → calcitriol + oral calcium + phosphorus control → KDIGO 2017 guidelines: target Ca × PO₄ ≤ 4.4 mmol²/L² to reduce vascular calcifications; post-thyroidectomy - prediction and prevention: Bove 2011 - Surgery: PTH measured at H4 post-thyroidectomy → PTH <10 pg/mL → predictive of symptomatic hypocalcemia in 85 % of cases → systematic initiation of oral calcium + calcitriol if PTH <10 pg/mL at H4 → Edafe 2014 - British Journal of Surgery: meta-analysis → early PTH (H1-H6) → best predictor of post-thyroidectomy hypocalcemia → sensitivity 82 % + specificity 86 % |
| Chronic treatment of hypoparathyroidism Oral calcium - calcitriol - alphacalcidol - recombinant PTH - natpara - nephro-calcinosis - follow-up - targets |
Conventional treatment of chronic hypoparathyroidism: oral calcium carbonate or calcium citrate: dose: 1,000-2,000 mg/d of elemental calcium in 2-3 doses + calcium carbonate: taken with meals (requires gastric acidity for dissolution - less effective in patients on PPIs) → calcium citrate: can be taken outside meals + more effective in patients on PPIs or with achlorhydria + elements to avoid in combination: phytates (wheat bran + legumes in excess) + oxalates (spinach + rhubarb) → reduce calcium absorption; calcitriol (1,25-dihydroxy-vitamin D3 - Rocaltrol): reference treatment in hypoparathyroidism → replaces renal production of calcitriol normally stimulated by PTH → usual dose: 0.25-2 µg/d in 2 doses → titration according to calcemia and calciuria → survival with ACEI/ARA-2: do not withdraw calcitriol abruptly → regression → hypocalcemia → alphacalcidol (1α-hydroxyvitamin D3 - One-Alpha): pro-drug → hydroxylated to calcitriol by the liver → longer half-life → 1-4 µg/d → alternative to calcitriol → therapeutic targets (Bilezikian 2016 - Journal of Bone and Mineral Research - International Guidelines): corrected total serum calcium: 2.00-2.25 mmol/L (lower limit of normal - do not aim for 2.35-2.60 mmol/L → risk of nephro-calcinosis and renal lithiasis as PTH absent → no renal tubular reabsorption of calcium → relative hypercalciuria) + 24h calciuria: <7.5 mmol/d (female) + <8.5 mmol/d (male) → if hypercalciuria: reduce oral calcium + reduce calcitriol → consider thiazide diuretic (HCTZ 25 mg/d → increases tubular calcium reabsorption) + serum phosphorus: normal or slightly elevated (acceptable in absence of PTH) + magnesium: within norms → monitor and supplement if low; follow-up of treated chronic hypoparathyroidism: calcium + phosphorus + magnesium + creatinine + 24h calciuria → every 3 months initially → then every 6 months if stable + annual renal ultrasound (nephro-calcinosis + lithiasis) → fundus (cataract) → DXA bone densitometry (absence of PTH → less bone resorption → bone density often paradoxically high - Bilezikian 2016) + cardiovascular workup (QTc) + quality of life (chronic hypoparathyroidism significantly impairs quality of life - Underbjerg 2015 - European Journal of Endocrinology) ; recombinant parathyroid hormone - rhPTH 1-84 (Natpara) : hormone replacement therapy for hypoparathyroidism → daily SC injection (50-100 µg/d) → Bilezikian 2016 - New England Journal of Medicine (REPLACE study): RCT n=134 → rhPTH 1-84 → reduction of oral calcium by 50 % + reduction of calcitriol by 50 % + normalization of calcium in 53 % vs 2 % placebo → adverse effects: hypercalcemia if dose too high + CAUTION: osteosarcoma risk signals in rats in preclinical studies (prolonged exposure duration at high doses) → contraindicated if bone Paget + bone radiotherapy + unexplained elevation of alkaline phosphatases → recommended for hypoparathyroidism difficult to control despite optimal conventional treatment (persistent hypocalcemia or severe hypercalciuria on calcitriol) → approval: FDA (2015) + EMA (2017) → limited availability in Canada (compassionate use + awaiting full Health Canada approval) → alternative in development: TransCon PTH (sustained-release PTH) → phase III studies underway | Key data on chronic hypoparathyroidism treatment: Bilezikian 2016 - Journal of Bone and Mineral Research: international hypoparathyroidism guidelines + 73 experts + Bilezikian 2016 - NEJM (REPLACE study): rhPTH 1-84 → reduced oral calcium dependence + calcium normalization + improved quality of life → founder result → Underbjerg 2015 - European Journal of Endocrinology: n=688 hypoparathyroid patients + comparison with general population → significantly impaired quality of life (physical + mental + fatigue) → more frequent anxiety + depression + Edafe 2014 - British Journal of Surgery: meta-analysis 52 studies → PTH at H4 post-thyroidectomy = best predictor of post-operative hypocalcaemia → guides early supplementation → reduced hospital admissions + Mannstadt 2017 - Nature Reviews Disease Primers: epidemiology + prevalence of chronic post-surgical hypoparathyroidism in Europe: 22/100,000 person-years + estimated prevalence 37,000 people + Canada: estimated prevalence 3,000-5,000 cases → conventional treatment unsatisfactory in 20-30 % of patients (persistent hypocalcemia or hypercalciuria) + Sanders 2019 - Endocrine: thiazide (chlorthalidone 25 mg/d) in hypoparathyroidism with hypercalciuria → reduction of calciuria by 25-30 % → reduced risk of nephro-calcinosis |
| Special populations and situations Post-thyroidectomy - infant - CKD - rickets - pregnancy - nephro-calcinosis - DiGeorge - APS-1 |
Post-thyroidectomy hypocalcemia - prevention and management: monitoring: PTH at H1-H4 postoperatively + calcium at H6 and H24 → if PTH <10 pg/mL at H4 → systematic initiation of oral calcium (1,000-2,000 mg/d) + calcitriol 0.25 µg 2×/d → Bove 2011 - Surgery: systematic protocol → reduction in hospitalizations for symptomatic hypocalcemia → IV calcium if symptoms or calcium 6 months) → chronic treatment according to guidelines; neonatal hypocalcemia: early neonatal hypocalcemia (D1-J3): prematurity + IUGR + son of diabetic mother + neonatal asphyxia + hypomagnesemia → calcium gluconate IV 200 mg/kg/d → late neonatal hypocalcemia (D5-J7): phosphorus-rich milks + hyperphosphatemia → transient hypoparathyroidism + maternal deficiency rickets → native vitamin D + oral calcium + genetic diagnosis if persistent → DiGeorge (22q11.2): immune workup (T lymphocytes) + echocardiography + ENT → chronic calcium + calcitriol if permanent hypoparathyroidism; hypocalcemia and CKD - secondary and tertiary hyperparathyroidism: CKD → 1α-hydroxylase defect → low calcitriol + phosphorus retention → hyperphosphatemia → hypocalcemia → secondarily elevated PTH → KDIGO 2017 goals: normal phosphorus + normal calcium + PTH 2-9× upper limit of normal (moderately elevated PTH needed to maintain bone remodeling in CKD) → treatment: IV or oral calcitriol + sevelamer (phosphorus binder) + cinacalcet (calcimimetic if very high PTH) → tertiary hyperparathyroidism (parathyroid autonomization after transplantation or prolonged CKD) → hypercalcemia + very high PTH → subtotal or total parathyroidectomy with autotransplantation → then post-operative hypocalcemia (hungry bone syndrome often intense); carential rickets - management: vitamin D3 (cholecalciferol) 2,000-4,000 IU/d × 3 months + calcium 500 mg/d + then vitamin D3 400-1,000 IU/d maintenance → Holick 2011 - Journal of Clinical Endocrinology and Metabolism: vitamin D guidelines → defined deficiency <50 nmol/L (25-OHD) → recommended treatment + therapeutic target: 25-OHD ≥75 nmol/L → Munns 2016 - Journal of Clinical Endocrinology and Metabolism: global consensus on prevention and treatment of deficiency rickets → vitamin D + calcium + maternal supplementation during pregnancy and lactation + pregnancy and hypocalcemia: frequent maternal vitamin D deficiency → recommended supplementation: vitamin D3 600-2,000 IU/d throughout pregnancy → ACOG 2021 + Hypoparathyroidism and pregnancy: calcium + calcitriol requirements increase in 3rd trimester + breastfeeding → requirements further increased → adjust calcitriol doses + monitor blood calcium levels monthly + risk of neonatal hypocalcemia if hypoparathyroid mother insufficiently treated | Vitamin D supplementation recommendations in Canada: Osteoporosis Canada 2022 + SCP 2023: adults <50 years: 400-1,000 IU/d vitamin D3 maintenance → adults ≥50 years: 800-2,000 IU/d → pregnancy + breastfeeding: 400-2,000 IU/d → breastfed infants: 400 IU/d from birth → at-risk populations (dark skin + covering clothing + low sun exposure + obesity + malabsorption): 800-2,000 IU/d → correction of documented deficiency (25-OHD <50 nmol/L): vitamin D3 50,000 IU/week × 8-12 weeks (prescribing physician) → then maintenance 800-2,000 IU/d → Holick 2011 - JCEM: treatment of vitamin D deficiency → 50,000 IU/week vitamin D2 or D3 × 8 weeks → then 1,500-2,000 IU/d → Munns 2016 - JCEM: international consensus rickets → systematic vitamin D + calcium in all countries → in areas with low sunshine + diet low in vitamin D → universal supplementation of infants + prevention in high-risk populations (immigrants from tropical countries + veiled women + elderly people in institutions): public health priority → Rosen 2012 - NEJM: comprehensive review of vitamin D + randomized studies: no additional cardiovascular benefit demonstrated at high doses (VITAL trial Manson 2019 - NEJM) but bone and muscle benefit recognized at physiological doses |
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Always check magnesium levels if hypocalcemia persists despite supplementation: profound hypomagnesemia (<0.5 mmol/L) inhibits PTH secretion and leads to peripheral resistance to PTH - rendering calcium supplementation ineffective. Magnesium correction (IV magnesium sulfate or oral magnesium, depending on severity) is an essential step before any other treatment. Furthermore, in chronic hypoparathyroidism, the calcium target is not full normality (2.15-2.60 mmol/L) but the lower limit (2.00-2.25 mmol/L): aiming higher exposes the patient to nephro-calcinosis and renal lithiasis in the absence of PTH.
Situations requiring a 911 call or urgent emergency consultation
Overt tetany with midwife's hand, generalized painful cramps, laryngeal stridor or convulsions → severe symptomatic hypocalcemia → call 911 → calcium gluconate 10 % IV (1-2 g in 10-20 min) → continuous ECG → ionized calcium monitoring → laryngeal tetany: risk of asphyxia → prepare for intubation → never inject calcium as a direct bolus.
Postoperative total thyroidectomy or parathyroidectomy patient with perioral paresthesia + tingling of extremities + positive Chvostek's sign → early post-surgical hypocalcemia → surgical or medical emergencies → oral calcium + calcitriol if moderate → IV calcium if severe + PTH at H4 post-op.
QTc prolongation on ECG (QTc >500 ms) + confirmed hypocalcemia → risk of malignant ventricular arrhythmias (torsades de pointes + ventricular fibrillation) → emergency hospitalization → continuous cardiac monitoring → IV calcium gluconate → correction of any aggravating causes (hypokalemia + hypomagnesemia + QT-prolonging drugs).
Infants or children with stridor, tetany or hypocalcemic convulsions → pediatric emergencies → pediatric IV calcium gluconate (50-100 mg/kg in 10 min) + ECG + monitoring → urgent etiological workup (DiGeorge 22q11.2 to be excluded) + neonatology or specialized pediatrics.
Consult at Clinique Omicron
Les médecins de Clinique Omicron évaluent les hypocalcémies découvertes en ambulatoire, prescrivent et interprètent le bilan étiologique complet (PTH, 25-OHD, magnésium, phosphore, calciurie), initient la supplémentation en vitamine D et en calcium selon les recommandations en vigueur, et orientent vers l'endocrinologue si une hypoparathyroïdie chronique ou une résistance à la PTH est suspectée. Des consultations sont disponibles dans plusieurs points de service au Québec et en télémédecine. Pour prendre rendez-vous, choisissez votre service en ligne.
The contents of this page are provided for information purposes only and do not replace medical advice. Symptomatic hypocalcemia (tetany, convulsions, arrhythmia) is a medical emergency requiring immediate hospital evaluation.
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