Hypoparathyroidism

• Iatrogenic (most common cause):
  • Thyro/parathyroidectomy
  • Neck dissection
  • Radiation
• Idiopathic/familial hypoparathyroidism
• Autoimmune parathyroid destruction: autoimmune polyendocrine syndrome type 1
• Genetic: DiGeorge syndrome (triad of: conotruncal cardiac anomalies, hypoplastic thymus (→ T cell immunodeficiency), and hypocalcemia (from parathyroid hypoplasia)
• Infiltrative disease of the parathyroid glands :
  • Hemochromatosis
  • Wilson’s disease

Acute manifestations

• Symptoms of hypocalcemia, such as tetany (see "Clinical features of hypocalcemia.")

Chronic

• Basal-ganglia calcifications:
  • Parkinsonism
  • Dementia
• Coarse, brittle hair and dry skin
• Tetanic cataracts (paradox intraocular lens calcification)
• Decreased insulin secretion
• Osteosclerosis, cortical thickening, craniofacial abnormalities
• Dental abnormalities when hypocalcemia is present in early childhood
• Idiopathic familial hypoparathyroidism may be associated with immune disorder and moniliasis.

History:

• Recent neck surgery/ thyroidectomy / parathyroidectomy
• Family history
• Genetic syndromes

Physical exam:

• Chvostek’s sign: Tapping on the facial nerve in the area of the cheek results in the twitching of the mouth musculature.
• Trousseau’s sign: muscle spasms of the hand (“claw”) after BP-cuff inflation of the arm
• Dry, puffy skin
• Alopecia , thin/brittle hair

Laboratory studies:

• ↓ Serum PTH levels
• ↓ Ca and ↑ phosphate levels in serum
• ↓ Phosphate levels in urine
• Urine Ca level can be low or high depending on the degree of serum Ca correction.
• Document normal levels of serum magnesium , creatinine , and 25-hydroxyvitamin D

• Pseudohypoparathyroidism : an autosomal dominant disorder with end-organ resistance to PTH secondary to a mutation in G protein (GNAS). Parathyroid hormone is secreted normally, but kidneys and bones are resistant to its effects, which leads to hypocalcemia , hyperphosphatemia , and increased serum PTH levels. Treatment is with Ca and vitamin D supplementation.
• Secondary hyperparathyroidism : secondary elevation of serum PTH due to hypocalcemia usually associated with CKD . Diagnosis is established based on elevated PTH levels in the setting of hypocalcemia and hyperphosphatemia . Management is focused on treating the underlying disease.
• Hypomagnesemia : low serum magnesium levels. Hypomagnesemia causes hypocalcemia by impairing PTH release in response to low serum Ca levels as well as by inducing bone PTH resistance . Hypocalcemia responds promptly to the restoration of normal magnesium levels.

• Treat underlying disease
• Calcium and vitamin D supplementation
• Recombinant human PTH can reduce the amount of supplemental calcium and vitamin D required.