Background
The normal action of parathyroid hormone (PTH) is to increase serum calcium levels and decrease serum phosphate levels. PTH affects the kidneys by increasing calcium reabsorption, decreasing renal phosphate reabsorption, and increasing active vitamin D formation, and affects the bones by increasing osteoclast activity.

Parathyroid Hormone Action.
Vitamin D Mechanism of Action.

Laboratory testing which suggests primary hypoparathyroidism includes decreased PTH, hypocalcemia, and hyperphosphatemia.

Patients may present with symptoms of hypocalcemia: paresthesias (especially of the lips, mouth, and fingertips), cramping, tetany, carpopedal spasm, altered mental status, irritability, mood swings, anxiety, stridor and hoarseness, wheezing and bronchospasm, diaphoresis and seizures.

Treatment of primary hypoparathyroidism:

While PTH analogs are used to treat osteoporosis, they are not FDA approved for hypoparathyroidism. As such, calcium and vitamin D are the mainstays of treatment.

The classic symptoms of hypoparathyroidism are those of insufficient calcium. Typically these include refractory heart failure, tetany, seizures, altered mental status, and stridor. Refractory heart failure is related to the low calcium interfering with the normal contractility of myocytes.

Low vitamin D can cause hypocalcemia but is not caused by it. That is, low vit D can cause hypocalcemia but hypocalcemia cannot cause low Vit D. ” ABFM critique.

Reference

N Engl J Med 2008;359(4):391-403.

Am Fam Physician 2013;88(4):249-257.

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