Hypoparathyroidism

Under physiologic circumstances, calcium concentration in the extracellular fluid is maintained within a narrow range. Normal calcium homeostasis depends on a complex set of hormonal regulatory mechanisms that include the effects of parathyroid hormone (PTH), vitamin D metabolites, and calcitonin on calcium transport in bone, kidneys, and the gastrointestinal tract. Hypoparathyroidism is an uncommon endocrine abnormality in which parathyroid gland dysfunction causes parathyroid hormone deficiency. Subsequently, this absence or decreased level of PTH results in hypocalcemia, hyperphosphatemia, and increased neuromuscular irritability. Patients typically present with symptoms consistent with hypocalcemia, including myalgias, muscle spasms, twitching, new-onset seizures, and in extreme cases, tetany. Symptom severity varies depending on the calcium level and duration of parathyroid dysfunction. Cardiac symptoms associated with conditions such as acute cardiomyopathy and congestive heart failure that result from impaired contractility secondary to hypocalcemia may also occur. Though there are multiple causes of hypoparathyroidism, unintended excision or iatrogenic injury during head and neck surgery (eg, thyroidectomy) is the most common etiology.

Hypoparathyroidism is typically diagnosed with laboratory studies confirming a low corrected calcium level as well as a decreased or undetectable parathyroid hormone level. Other findings that support this diagnosis include elevated serum phosphorus, decreased 1,25-dihydroxyvitamin D, and elevated urinary fractional calcium excretion levels. Hypoparathyroidism treatment primarily consists of correcting calcium, vitamin D, and magnesium deficiencies with supplementation. Within the last several years, recombinant human parathyroid hormone became available and is currently used as replacement therapy in patients unresponsive to supplementation. The most common complications of hypoparathyroidism are chronic kidney disease and kidney stones. Other complications include cataracts, cognitive dysfunction, cardiac arrhythmias, anxiety, and depression.