Diagnosis

Hypoparathyroidism

Etiology

Cause [hap]

• Postsurgical: thyroid, parathyroid, larynx surgery (78%, most common) [1ug][hap]

• Autoimmune

  • Autoimmune polyglandular syndrome-1

  • Isolated autoimmune hypoparathyroidism

• Infiltrative

  • Granulomatous disease

  • Sarcoidosis

  • Amyloidosis

  • Metastatic cancer

  • Riedel struma

  • HIV

• Destructive

  • Radiation

• Metal deposition

  • Wilson’s disease (copper)

  • Hemochromatosis (iron)

  • Transfusion dependence (iron)

  • Aluminum toxicity

• Metabolic causes

  • Hypermagnesemia

  • Hypomagnesemia

  • Burn injury

  • Fetal exposure to retinoids, alcohol or hyperglycemia or maternal hypercalcemia

• Toxic agents: Asparaginase, Ethiofos, immune checkpoint inhibitors

• Genetic disorders: DiGeorge Sequence; TBX; CHARGE syndrome, HDR syndrome (Barakat syndrome); Sanjad-Sakati syndrome, and Kenny-Caffey syndrome; Smith-Lemli-Opitz syndrome

• Mitochondrial disorders: Kearns-Sayre syndrome; Pearson Marrow-Pancreas syndrome; MELAS syndrome

• Idiopathic

Pathophysiology [soa]

1. Calcium homeostasis is regulated by:

   • Parathyroid hormone (PTH)

   • Vitamin D metabolites

   • Calcitonin

2. The mechanism control calcium transport in bone, kidneys, and the GI tract

3. Hypoparathyroidism --> PTH fail to rise in response to hypocalcemia --> no mobilization of the skeleton or increase in renal resorption --> hypocalcemia

Complications [soa]

• Kidney failure

• Kidney stones

• Cataracts

• Cognitive dysfunction

• Cardiac arrhythmia

• Anxiety

• Depression

Epidemiology

Incidence per 100.000 [3tz][29e][knq][hap][iqw][gdk][nei][1ug]

Prevalence per 100.000 [3tz][29e][knq][hap][iqw][gdk][nei][1ug]

Approach

• Blood test: PTH, serum calcium, phosphate, magnesium, albumin, creatinine, fT4, TSH, vitamin D [iqw][soa]

• 24-hour urine calcium and creatinine

• ECG

• Renal ultrasound

• Abdominal CT

Treatment

1. Acute onset with severe hypocalcemia: intravenous calcium administration [soa]

   • IV calcium bolus of 90-180 mg infused over 10-20 minutes with cardiac monitoring

   • Maintenance IV calcium infusion of 900 mg Ca in 1 L of saline at a rate of 50 mL/hr

   • Corrected calcium = measured total calcium + [0.8 x(4-measured serum albumin)]

2. Chronic hypoparathyroidism: [kdq]

   • Treatment goals:

     • Keep patients asymptomatic

     • Maintain the calcemia slightly below or in the lower normal range

     • Calciuria up to 4 mg/kg/day

   • Calcium supplementation:

     • Calcium carbonate 2.5-7.5 g/day

     • Calcium citrate 5-15 g/day

   • Vitamin D

     • Calcitriol 0.25-2 mcg/day

     • Cholecalciferol 10,000 - 100,000 UI/day

   • Magnesium supplementation: 250-1,000 mg/day

   • Phosphate binder: Sevelamer 800 mg x 3

   • Thiazide diuretic: 12,5-100 mg/day

   • Subcutaneous PTH injection 25-100 mcg/day

Differential diagnoses

Clostridium tetani, Hyperkalemia, Hyperphosphatemia, Hyperventilation, Hypocalcemia, Hypocapnia, Hypokalemia, Hypomagnesemia, Hypoparathyroidism, Milk-alkali syndrome