- Clinical science
Hypoparathyroidism may be due to a variety of mechanisms, including destruction of parathyroid glands (autoimmune or surgical), abnormal parathyroid gland development, altered regulation of parathyroid hormone (PTH), or impaired PTH action on end organs. The resulting hypocalcemia can trigger a variety of symptoms, ranging from muscle cramps to seizures or heart failure. Manifestations of chronic hypoparathyroidism, however, are quite specific, and include basal ganglia calcifications (resulting in movement disorders), cataracts, and skeletal and dental abnormalities. Laboratory findings in hypoparathyroidism include hypocalcemia with low or inappropriately normal PTH, hyperphosphatemia, and normal renal function. Treatment usually includes correcting the hypocalcemia through calcium and vitamin D supplementation and treatment of the underlying cause.
- Postoperative: most commonly occurs as the result of accidental injury to parathyroids (or their blood supply) during thyroidectomy, parathyroidectomy, or radical neck dissection
- Autoimmune: second most common cause
- Nonautoimmune destruction:
- Acute manifestations
- Extrapyramidal disorders : symptoms include parkinsonism, dystonia, hemiballismus, choreoathetosis, oculogyric crises, or dementia
- Ocular disease: cataracts, keratoconjunctivitis
- Skeletal: increased bone mineral density, osteosclerosis
- Dental abnormalities: dental hypoplasia, failure of tooth eruption, defective root formation
- Cutaneous manifestations: dry, puffy, coarse skin
- See .
Pseudohypoparathyroidism type 1A: end-organ (i.e., bones and kidneys) resistance to parathyroid hormone (PTH) despite sufficient PTH synthesis due to a defective Gs protein alpha subunit
- Inheritance: autosomal dominant; gene defect inherited from the mother (GNAS gene imprinting)
- Pathophysiology: mutations in GNAS1 → α subunit is not encoded → impaired activation of adenylate cyclase when PTH binds to Gs → resistance to PTH in kidney and bone tissue
- Clinical features:
- Pseudopseudohypoparathyroidism: extremely rare condition that mimics PHP type 1a but without end-organ resistance to PTH
The differential diagnoses listed here are not exhaustive.