- Deficient or absent secretion of parathyroid hormone (PTH), a major hormone regulator of serum calcium and phosphorus levels in the body (1)
- Acute hypoparathyroidism: tetany that is mild (muscle cramps, perioral numbness, paresthesias of hands and feet) or severe (carpopedal spasm, laryngospasm, heart failure, seizures, stridor)
- Chronic: often asymptomatic; lethargy, anxiety/depression, urolithiasis and renal impairment, dementia, blurry vision from cataracts or keratoconjunctivitis, parkinsonism or other movement disorders, mental retardation, dental abnormalities, and dry, puffy, coarse skin
- System(s) affected: endocrine/metabolic, musculoskeletal, nervous, ophthalmologic, renal
- May occur in premature infants
- Neonates born to hypercalcemic mothers may experience suppression of developing parathyroid glands.
- Congenital absence of parathyroids
- May appear later in childhood as autoimmune
Hypocalcemia is fairly common in elderly, however, rarely secondary to hypoparathyroidism.
- Use of magnesium as a tocolytic may induce functional hypoparathyroidism.
- For women with hypoparathyroidism, calcitriol requirements decrease during lactation.
More common in women; affects all ages
- Most common after surgical procedure of the anterior neck, particularly when the surgeon performs few anterior neck dissections (<50–100 thyroidectomies/parathyroidectomies per year).
- Transient hyperparathyroidism is common (6.9–46% of thyroidectomies), whereas permanent hypoparathyroidism differs depending on surgeon and facility expertise.
- Affects 24 to 37/100,000 persons per year in the United States (1)
- Genetic disorders account for <10% of all hypoparathyroidism, but represent a large proportion of cases in children.
Etiology and Pathophysiology
- PTH aids in regulating calcium homeostasis:
- Mobilizes calcium and phosphorus from bone stores
- Increases calcium absorption from the intestine by stimulating formation of 1,25-dihydroxy vitamin D
- Stimulates reabsorption of calcium in the distal convoluted tubule and phosphate excretion in proximal tubule
- Reduced or absent PTH action results in hypocalcemia, hyperphosphatemia, and hypercalciuria.
- Acquired hypoparathyroidism
- Surgical: removal or damage to parathyroid glands or their blood supply/enervation during neck surgery for thyroidectomy/parathyroidectomy, or neck surgery for head and neck cancers (2)
- Autoimmune: isolated or combined with other endocrine deficiencies in polyglandular autoimmune (PGA) syndrome
- Deposition of heavy metals in gland: copper (Wilson disease) or iron (hemochromatosis, thalassemias), radiation-induced destruction, and metastatic infiltration
- Functional hypoparathyroidism: may result from hypomagnesemia or hypermagnesemia because magnesium is crucial for PTH secretion and activation of the PTH receptor
- Calcium-sensing receptor (CaSR) abnormalities: hypocalcemia with hypercalciuria
- HDR or Barakat syndrome: deafness, renal dysplasia
- Familial: mutations of the TBCE gene; abnormal PTH secretions
- 22q11.2 deletion syndrome
- Autoimmune: genetic gain-of-function mutation in CaSR
- Infiltrative: metastatic carcinoma, hemochromatosis, Wilson disease, granulomas
- X-linked or in autosomal recessive mutations in the transcription factor glial cell missing B (GCMB)
- Mutations in transcription factors or regulators of parathyroid gland development
- Component of a larger genetic syndrome (APS-1 or DiGeorge syndrome) or in isolation (X-linked hypoparathyroidism) (3)
- May be autosomal dominant (DiGeorge), autosomal recessive (APS-1), or X-linked recessive (X-linked hypoparathyroidism) (3)
- Congenital syndromes
- 22q11.2 deletion syndrome, familial hypomagnesemia, hypoparathyroidism with lymphedema (3)
- Hypoparathyroidism with sensorineural deafness
- ADHH: mutations gain-of-function of the CaSR gene suppressing the parathyroid gland, without elevation of PTH
- PGA syndrome type I: mucocutaneous candidiasis, hypoparathyroidism, and Addison disease
Neck surgery and neck trauma, neck malignancies, family history of hypocalcemia, PGA syndrome
Intraoperative identification and preservation of parathyroid tissue
Commonly Associated Conditions
- DiGeorge syndrome
- Bartter syndrome
- PGA syndrome type I
- Multiple endocrine deficiency autoimmune candidiasis (MEDAC) syndrome
- Juvenile familial endocrinopathy
- Addison disease
- Moniliasis (HAM) syndrome: a polyglandular deficiency syndrome, possibly genetic, characterized by hypoparathyroidism
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