Transplant surgery that moves two or more parathyroid glands and places them elsewhere in a patient — a process called autotransplantation — can prevent postoperative hypoparathyroidism after the thyroid is totally removed in people with cancer in that gland, researchers report.
Their study, “Postoperative hypoparathyroidism after total thyroidectomy for thyroid cancer,” was published in the journal Auris Nasus Larynx.
Most patients with well-differentiated thyroid cancer have excellent overall survival rates. In some cases, physicians will conduct a thyroidectomy — removal of the thyroid gland — to treat the cancer.
During this procedure, parathyroid glands (PTGs) — small glands located in the neck that produce the parathyroid hormone — are at risk of being damaged, mainly due to inadvertent removal, interruption of the blood supply, or a hematoma.
This can lead to hypoparathyroidism, one of the most common complications in total thyroidectomy for thyroid carcinoma, occurring in 10-60% of cases.
People have four parathyroid glands. Ideally, those glands would be preserved during a thyroidectomy — but practically this is not always possible, and damage to one or more glands can be unpredictable. For these reasons, surgeons may opt to autotransplant intact parathyroid glands.
Parathyroid autotransplantation involves taking parathyroid tissue and placing it into muscles in the neck or forearm. Parathyroid tissue is generally cut into very tiny pieces, 1-2 mm, and placed in small compartments within the muscle. Within four to six weeks, the transplanted gland typically develops a new blood supply and begins to work.
Japanese researchers at Kobe University Graduate School of Medicine assessed the effectiveness of their surgical procedure to preserve parathyroid function, and to determine potential risk factors of postoperative hypoparathyroidism in thyroid cancer patients undergoing a total thyroidectomy.
A total of 65 patients — with and without intact parathyroid glands — were included in the retrospective study. Cancers were diagnosed at stage 1 in 15 patients, stage 2 in 24 patients, stage 3 in 19 patients, and stage 4 — the most advanced stage — in seven patients.
Loss of parathyroid gland function was defined as permanent postoperative hypoparathyroidism, with patients requiring vitamin D supplementation — with or without calcium — for more than six months after a total thyroidectomy. Postoperative transient hypoparathyroidism was defined as patients requiring the same post-surgery supplements, but for no more than six months.
Postoperative transient hypoparathyroidism was reported in 44 (68%) of these patients, and permanent hypoparathyroidism in 12 (18%).
Among 34 patients with intact parathyroid glands that did not require an autotransplant, transient hypoparathyroidism was reported in 17 people and permanent hypoparathyroidism in six.
The remaining 31 patients did not have intact parathyroid glands. Postoperative permanent hypoparathyroidism was observed in four who did not receive an PTG autotransplant (due to locally advanced disease), and in six of 18 patients who had one gland that was autotransplanted.
Importantly, none of the nine patients who underwent an autotransplant of two or more parathyroid glands developed permanent hypoparathyroidism.
An analysis of risk factors for permanent postoperative hypoparathyroidism found it was significantly higher in patients with large tumors — greater than 40 mm — and/or a tumor that had spread beyond the thyroid gland.
“Two or more PTG should be autotransplanted in case where PTG is not preserved in situ [in its original site] to prevent postoperative HPT [hypoparathyroidism] after total thyroidectomy with central neck dissection, especially in cases of large tumor and/or gross extrathyroidal extension,” the researchers concluded.