The incidence of thyroid cancer has increased dramatically during the past three decades and it is now the fastest growing cancer in women. One recent estimate indicated that there were >470,000 new cases of thyroid cancer globally in 2015. If recent trends are maintained, thyroid cancer may become the fourth most common cancer by 2030 in the United States. Papillary carcinoma is the most common form of well-differentiated thyroid cancer and thyroid surgery (partial or complete thyroidectomy) is the definitive approach to management of this malignancy.
Hypoparathyroidism is a common complication following bilateral thyroid surgery. Temporary hypoparathyroidism occurs in approximately 10% to 30% of patients, whereas permanent hypoparathyroidism has been reported in 1% to 3%. The risk of hypoparathyroidism increases with the extent of thyroidectomy, re-operative procedures, and central neck clearance. Parathyroid identification and preservation are essential components of safe thyroid surgery. Achieving this goal is important because post-surgical hypoparathyroidism has been associated with a large number of complications, including renal insufficiency, nephrolithiasis, neuropsychiatric complications, and increased risk for infections. Mineral imbalances in patients with hypoparathyroidism secondary to thyroid surgery may also result in increased risk for the development of cardiovascular disease. Post-surgical hypoparathyroidism also results in impaired quality of life.
Careful dissection with identification and preservation of parathyroid glands in situ remains the best way to maintain gland vitality and avoid post-operative failure. Nevertheless, parathyroid glands are still inadvertently removed in up to 11% of cases. Non-invasive approaches to reliably localize parathyroid glands during surgery are needed and the use of indocyanine green and fluorescence monitoring may help to address this problem.
Current options for replacement of parathyroid hormone (PTH) in patients who have had damage to or inadvertent removal of the parathyroid glands include parathyroid auto-transplantation, which has variable efficacy in preventing the incidence of permanent hypoparathyroidism, and replacement therapy with recombinant human PTH(1-84), which has been shown to be effective in several clinical trials. Additional alternatives in development include long-acting PTH analogues and transplantation of mesenchymal stem cells conditioned to release PTH.
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