Hypoparathyroidism

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Description

  • Deficient or absent secretion of parathyroid hormone (PTH) (1)
  • Acute hypoparathyroidism: mild tetany (muscle cramps, perioral numbness, paresthesias of hands and feet) or severe (carpopedal spasm, laryngospasm, heart failure, cardiac arrhythmias, seizures, stridor)
  • Chronic: often asymptomatic; lethargy, anxiety/depression, urolithiasis and renal impairment, dementia, blurry vision, parkinsonism or other movement disorders, dental abnormalities, and dry, puffy, coarse skin, ischemic heart disease
  • System(s) affected: endocrine/metabolic, musculoskeletal, nervous, ophthalmologic, renal, cardiac, psychiatric

Pediatric Considerations

  • May occur in premature infants
  • Maternal hypercalcemia can result in infantile hypocalcemia with suppressed parathyroid development.
  • Infants of mothers with hypocalciuric hypercalcemia can also have hypoparathyroidism (hypoPTH).
  • Congenital absence of parathyroids
  • Autoimmune hypoparathyroidism appears later in childhood

Pregnancy Considerations

  • For women with hypoparathyroidism, calcium and calcitriol requirements may change, so close monitoring of serum calcium adjusted for albumin q3–4wk during pregnancy
  • Hypocalcemia in pregnancy is associated with uterine contractions and an increased risk of preterm labor or miscarriage.
  • Maternal hypocalcemia can be associated with secondary fetal hyperparathyroidism (hyperPTH) causing skeletal complications and fractures.

Epidemiology

More common in women; affects all ages

Incidence

  • Chronic hypoPTH—0.8 to 2.3/100,000 per person-years
  • Transient/temporary after total thyroidectomy—20–30%
  • Most common after anterior neck surgery, particularly when the surgeon performs few anterior neck dissections (<50 to 100 per year)
  • Transient hyperPTH is common (6.9–46% of thyroidectomies).

Prevalence

  • 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; reduced or absent PTH results in hypocalcemia, hyperphosphatemia, and hypercalciuria.
  • Acquired hypoparathyroidism
    • Surgical: removal or damage to parathyroid glands during neck surgery (2) (hungry bone syndrome)
    • Autoimmune: isolated/acquired disease or combined with other endocrine deficiencies in polyglandular autoimmune (PGA) syndrome
    • Deposition of heavy metals in gland: copper (Wilson disease) or iron (hemochromatosis, thalassemias), aluminium, radiation-induced destruction, and infiltration (metastatic, granulomatous, inflammatory or amyloid protein)
    • Functional/transient hypoparathyroidism: may result from hypomagnesemia or hypermagnesemia because magnesium is crucial for PTH secretion and activation of the PTH receptor
    • Congenital
  • Infiltrative: metastatic carcinoma, hemochromatosis, Wilson disease, granulomas

Genetics

  • 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

Risk Factors

Neck surgery and neck trauma, neck malignancies, family history of hypocalcemia, PGA syndrome

General Prevention

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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