Hypoparathyroidism

Hypoparathyroidism has wide variety of presentations: from the asymptomatic patient with dramatically low serum calcium to the acutely symptomatic patient with neuromuscular irritability, tetany, painful muscle cramps, stridor, and even seizures with low serum calcium in the accident and emergency department or recovery room.

Majority of cases are post-surgery for benign and malignant thyroid disorders, hyperparathyroidism, and laryngeal or other head and neck cancers.

Nonsurgical aetiologies include: rare genetic conditions and syndromes; autoimmune destruction of the glands; destruction or invasion due to tumour, radiation, or infiltration by iron or copper; hypomagnesaemia and magnesium depletion; and idiopathic.

Laboratory testing should confirm low ionised or albumin-corrected total calcium and low or inappropriately normal intact plasma parathyroid hormone (PTH), while also verifying normal serum magnesium and 25-hydroxyvitamin D levels.

If symptoms are present, replacement of calcium and/or magnesium should be promptly instituted with careful monitoring along with activated vitamin D metabolites for chronic treatment.

The disorder is caused by relative or absolute deficiency of plasma parathyroid hormone (PTH) synthesis and secretion. This leads to low albumin-corrected serum total calcium and elevated serum phosphate. Signs and symptoms can involve the neuromuscular, psychiatric, cardiac, ocular, dermatological, gastrointestinal, and renal/urological systems. Patients can also be asymptomatic. [1] Shoback DM, Bilezikian JP, Costa AG, et al. Presentation of hypoparathyroidism: etiologies and clinical features. J Clin Endocrinol Metab. 2016;101:2300-2312. http://www.ncbi.nlm.nih.gov/pubmed/26943721?tool=bestpractice.com [2] Shoback D. Clinical practice. Hypoparathyroidism. N Engl J Med. 2008;359:391-403. http://www.ncbi.nlm.nih.gov/pubmed/18650515?tool=bestpractice.com [3] Bilezikian JP, Khan A, Potts JT Jr, et al. Hypoparathyroidism in the adult: epidemiology, diagnosis, pathophysiology, target-organ involvement, treatment, and challenges for future research. J Bone Miner Res. 2011;26:2317-2337. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3405491/ http://www.ncbi.nlm.nih.gov/pubmed/21812031?tool=bestpractice.com Definitions of permanent post-surgical hypoparathyroidism vary, but persistently low intact PTH levels in the presence of hypocalcaemia requiring treatment for at least 6 months post-procedure generally indicates the condition is permanent.