Hypoparathyroidism

Hypoparathyroidism 

Updated: 07/02/2023

© Jun Wang, MD, PhD

General features
  • Primary: Inadequate PTH activity
  • Secondary: Low PTH levels in response to a primary process that causes hypercalcemia
Etiology
  • Post-surgical: Most common cause, especially for acute presentation
  • Genetic disorders
Abnormal parathyroid gland development
Abnormal PTH synthesis
Activating mutations of calcium-sensing receptor (autosomal dominant hypocalcemia or sporatic isolated hypoparathyroidism)
  • Autoimmune
Polyglandular autoimmune syndromes (associated with chronic mucocutaneous candidiasis and primary adrenal insufficiency)
Isolated hypoparathyroidism due to activating antibodies to calcium-sensing receptor
  • Infiltration of the parathyroid gland (granulomatous, iron overload, metastases)
  • Radiation-induced destruction parathyroid glands
  • Hungry bone syndrome (post parathyroidectomy)
  • HIV infection
Clinical presentations
  • Associated with hypocalcemia
  • Acute 
    •  Neuromuscular irritability ranging from mild (peri-oral numbness, paresthesias of the hands and feet, muscle cramps) to severe (carpopedal spasm, laryngospasm, and focal or generalized seizures)
  • Chronic 
    • Basal ganglia calcifications: due to hyperphosphatemia and subsequently increased calcium phosphorus product deposited in tissue
    • Cataracts
    • Mood swings and/or personality disturbances, dental abnormalities, cardiovascular and skin manifestations (dry, puffy, and coarse)
  • Chvostek sign: Twitching of ipsilateral facial muscle after tapping the muscles
  • Trousseau sign: Muscle contraction of forearm after brachial artery compressed by a sphygmomanometer above systolic pressure
  • Psychiatric disturbance and cardiac conduction defects (prolonged QT intervals)
    Polyglandular autoimmune syndrome type 1
    • AKA autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) or as Whitaker syndrome
    • Very rare in the States, but shows clusters in Finns, Sardinians, and Iranian Jews
    • Autoimmune multiple endocrine gland insufficiencies
    • Associated with candidiasis, hypoparathyroidism, and adrenal failure
    • 3 main types of autoantibodies: Against the surface receptor molecules, intracellular enzymes, and secreted proteins
    • Monogeneic mutation of AIRE (autoimmune regulator)
    Autosomal-dominant hypoparathyroidism
    • Gain of function mutation of calcium-sensing receptor
    • Overactive CaSR resulting in inhibition of PTH release even at low calcium level
    • Majority asymptomatic
    • Hypocalcemia and hypercalciuria, with normal or low PTH
    • May have low serum magnesium
    • Recurrent nephrolithiasis and nephrocalcinosis, particularly during treatment with vitamin D and calcium supplementation
    Familial isolated hypoparathyroidism
    • A group of extremely rare genetic disorders of hypoparathyroidism
    • Classified based on genetic alterations: GCM2, pre-proPTH
    • Hypocalcemia associated symptoms and signs: Fatigue, muscle weakness, twitching and cramping of the extremities, or spasms of the hands, feet, arms, or face
    • Diagnosis based on clinical presentations, lab tests and molecular genetics
    • Goal of treatment: Normalize calcium, with Vitamin D analogs etc
    Diagnosis
    • Persistent hypocalcemia
    • Low or inappropriately normal parathyroid hormone (PTH) level
    • Hyperphosphatemia
    • Absence of hypomagnesemia
    Treatment
    • Symptom relieve
    • Raise calcium
    • Prevent iatrogenic kidney stone


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