What is Hypoparathyroidism?

Hypoparathyroidism is a rare condition where the parathyroid glands produce too little or no parathyroid hormone (PTH). This leads to low calcium (hypocalcemia) and high phosphorus (hyperphosphatemia) in the blood.

Causes:

Post-Surgical (Most Common Cause – 75%):

• Damage or removal of parathyroid glands during thyroid or parathyroid surgery
• Can be temporary (transient, resolving within weeks-months) or permanent

Autoimmune:

• Isolated autoimmune hypoparathyroidism
• Part of Autoimmune Polyglandular Syndrome Type 1 (APS-1)

Congenital/Genetic:

• DiGeorge Syndrome (22q11.2 deletion)—absent or hypoplastic parathyroid glands
• X-linked hypoparathyroidism
• Familial isolated hypoparathyroidism

Infiltrative Diseases:

• Hemochromatosis, Wilson's disease
• Metastatic cancer to parathyroid glands (rare)

Radiation:

• Radioactive iodine treatment (for thyroid cancer or hyperthyroidism)

Magnesium Abnormalities:

• Severe hypomagnesemia or hypermagnesemia can suppress PTH secretion (functional hypoparathyroidism—reversible)

Symptoms (Due to Low Calcium):

Acute/Severe Hypocalcemia:

• Neuromuscular Irritability:
  • Tetany: Involuntary muscle spasms (hands, feet, face)
  • Carpopedal Spasm: "Trousseau's Sign"—hand/wrist spasm when blood pressure cuff inflated
  • Chvostek's Sign: Facial twitching when tapping facial nerve
  • Paresthesias: Tingling/numbness around mouth, fingers, toes
• Seizures (if severe)
• Laryngospasm: Throat spasm—life-threatening
• Arrhythmias, Prolonged QT Interval: Risk of sudden cardiac death

Chronic Hypocalcemia:

• Fatigue, weakness
• Muscle cramps, aches
• Cognitive impairment, "brain fog"
• Depression, anxiety, irritability
• Dry, coarse skin; brittle nails
• Hair loss
• Cataracts
• Basal Ganglia Calcifications: Can cause movement disorders (Parkinsonism)
• Dental abnormalities (if congenital—enamel hypoplasia)

Diagnosis:

Lab Findings:

• Low Serum Calcium: Total calcium <8.5 mg/dL or ionized calcium <4.6 mg/dL
• Low or Inappropriately Normal PTH: Should be elevated in response to low calcium; in hypoparathyroidism, it's low or normal
• High Phosphorus: >4.5 mg/dL (PTH normally lowers phosphorus)
• Low or Normal 25-OH Vitamin D
• Low Magnesium: Check and correct (can cause functional hypoparathyroidism)

Additional Tests:

• ECG: Prolonged QT interval
• 24-Hour Urine Calcium: Usually low (but can be high if taking too much calcium/Vitamin D)
• Genetic Testing: If congenital/familial form suspected
• Brain CT/MRI: Check for basal ganglia calcifications

Treatment:

Acute Symptomatic Hypocalcemia (Emergency):

• IV Calcium Gluconate: 1-2 grams IV over 10-20 minutes, then continuous infusion
• Magnesium Repletion: If low magnesium present
• Monitor ECG, calcium levels frequently

Chronic Management:

1. Calcium Supplementation:

• High-Dose Calcium: 1500-3000 mg/day (divided doses with meals)
• Calcium carbonate (most calcium per tablet; take with food)
• Calcium citrate (better absorbed; can take without food)

2. Active Vitamin D (Calcitriol):

• Calcitriol (Rocaltrol®): 0.25-2 mcg/day (divided twice daily)
• Alfacalcidol: Alternative (not available in all countries)
• Active Vitamin D increases calcium absorption from gut
• Do NOT use regular Vitamin D (cholecalciferol) as primary treatment—it's less effective without PTH

3. Thiazide Diuretics (Sometimes Used):

• Reduce urinary calcium excretion
• Can help lower calcium dose requirements

4. Recombinant Human PTH (rhPTH):

• Palopegteriparatide (Yorvipath™): New FDA-approved daily injection for chronic hypoparathyroidism
• Replaces missing PTH
• Reduces need for high-dose calcium/Vitamin D
• Expensive; reserved for difficult-to-control cases

Goals of Treatment:

• Target Serum Calcium: Low-normal range (8.0-9.0 mg/dL)—NOT fully normal (to avoid hypercalciuria and kidney stones)
• Symptom Control: Prevent tetany, muscle cramps, seizures
• Avoid Complications: Kidney stones, nephrocalcinosis, kidney failure

Monitoring:

• Calcium and Phosphorus: Initially frequent (weekly), then every 3-6 months once stable
• Magnesium: Periodically
• Kidney Function (Creatinine): Every 6-12 months
• 24-Hour Urine Calcium: Annually (goal <300 mg/day to prevent kidney stones)
• Renal Ultrasound or CT: Baseline and periodically to check for kidney stones or nephrocalcinosis
• Ophthalmology: Annual eye exams (cataract screening)

Complications of Hypoparathyroidism:

• Kidney stones, nephrocalcinosis (from high calcium/Vitamin D treatment)
• Chronic kidney disease
• Basal ganglia calcifications (movement disorders)
• Cataracts
• Seizures, arrhythmias (if poorly controlled)
• Reduced quality of life (fatigue, cognitive issues)