Hypoparathyroidism

• • Paresthesias, muscle cramps, carpopedal spasm, laryngeal stridor, convulsions, malaise, muscle and abdominal cramps, tetany, urinary frequency, lethargy, anxiety, psychoneurosis, depression, and psychosis

  • History of central neck (thyroid, parathyroid, or laryngeal) resection

  • Positive Chvostek and Trousseau signs

  • Brittle and atrophied nails, defective teeth, cataracts

  • Hypocalcemia and hyperphosphatemia, low or absent urinary calcium, low or absent circulating parathyroid hormone (PTH)

  • Calcification of basal ganglia, cartilage, and arteries as seen on x-ray

Epidemiology

• • Although uncommon, occurs most often as a complication of thyroid surgery (especially for malignancy or recurrent goiter)

  • Idiopathic hypoparathyroidism is an autoimmune process and can be associated with autoimmune adrenocortical insufficiency

  • Rare, but possible, after radioiodine therapy for hyperthyroidism

  • Neonatal tetany associated with maternal hyperparathyroidism

Symptoms and Signs

• • Tetany

  • Positive Chvostek or Trousseau signs (or both)

  • Paresthesias, circumoral numbness, muscle cramps, irritability, carpopedal spasm, convulsions, opisthotonos, and marked anxiety

  • Dry skin, brittle nails, spotty alopecia

Laboratory Findings

• • Low serum calcium

  • Elevated serum phosphate

  • Low urinary calcium

  • Low or absent urinary phosphate

  • Low serum PTH

  • Low urine hydroxyproline

Imaging Findings

• • Calcification of the basal ganglia, arteries, and external ear

• • Most postoperative hypocalcemia is transient

Rule Out

• • Tetany from hyperventilation and alkalosis

  • Hypocalcemia from remineralization of bones after therapy for hyperparathyroidism ("hungry bones")

  • Hypocalcemia from intestinal malabsorption or renal insufficiency

  • Pseudohypoparathyroidsim (X-linked syndrome with defective renal adenylyl cyclase system; associated with round face, thick body, stubby fingers, mental deficiency, and x-ray evidence of calcifications; may have associated thyroid or ovarian dysfunction; patients do not respond with phosphaturia to PTH challenge; serum concentrations of PTH are increased; can be controlled with low dose vitamin D)

  • Pseudopseudohypoparathyroidism (thought to be common genetic defect as pseudohypoparathyroidism, but more mild; hypocalcemia only brought out during periods of stress such as pregnancy and rapid growth)

• • History and physical exam

  • Special note of prior neck surgery

  • Serum and urine tests for calcium, phosphate, and PTH

When to Admit

• • In the presence of acute hypoparathyroid tetany

• • Aim of treatment is to raise serum calcium levels, to bring the patient out of tetany (if present), and to lower serum phosphate levels (to prevent metastatic calcification)

  • Treatment is medical (unless parathyroid tissue was cryopreserved at the time of neck operation)

Medications

• • Oral calcium (calcium, lactate, or carbonate)

  • Calcitriol

  • IV calcium gluconate for acute tetany (6 g mixed in 500 mL DSW infused at 1 mL/kg/h)

  • Magnesium sulfate if also hypomagnesemic

  • Phosphorous limited diet, and possibly phosphate binders such as aluminum hydroxide gel