Permanent Hypoparathyroidism Can Take Year or More To Be Evident

Recovery of parathyroid function can take more than a year after thyroid gland removal, suggesting that longer follow-up periods could be needed to accurately diagnose permanent hypoparathyroidism, a study reported.

Its researchers followed patients who didn’t quickly recover for an average of 28 months after surgery in making a determination.

The study, “Duration of Parathyroid Function Recovery in Patients With Protracted Hypoparathyroidism After Total Thyroidectomy for Papillary Thyroid Carcinoma,” was published in the journal Frontiers in Endocrinology.

Surgical removal of the thyroid, a procedure called a thyroidectomy, is frequently performed to treat thyroid cancer. It is a common cause of  hypoparathyroidism, because the parathyroid glands can be accidentally damaged or removed.

Parathyroid hormone (PTH) levels typically rise within one month following surgery, as parathyroid function returns. Some people, however, experience a more persistent form of hypoparathyroidism, which is defined as permanent after six months, according to both European and U.S. guidelines.

However, how much follow-up should be done before declaring hypoparathyroidism to be “permanent” is still under debate.

The American Association of Clinical Endocrinologists, for instance, extended its recommended follow-up period to one year in 2015.

Researchers at Sichuan University’s West China Hospital, in Chengdu, conducted a study to determine how frequently patients with prolonged hypoparathyroidism recovered PTH levels, and how much time was needed for this to happen. They also looked at clinical variables associated with recovery.

The team followed 128 adults with protracted hypoparathyroidism following total thyroidectomy for thyroid cancer between July 2013 and June 2017.

Blood PTH and calcium levels were tested on the day after surgery. If below the normal range, patients would be given orally 1.5–3 g/day of calcium carbonate and 0.5–1.5 micrograms/day of calcitriol (active form of vitamin D). Calcium supplements would also be infused in cases of sudden hypocalcemia, or low calcium.

Of these 128 adults, 105 eventually recovered parathyroid function. It took up to six months for 86 of them (81.9%) to recover, and over six months for 19 others (18.1%). Eleven of these patients recovered function between six and 12 months, and eight others after one year post-thyroidectomy.

Patients age 55 or younger, or without high blood pressure, were more likely to recover, as were those whose surgeries included the use of carbon nanoparticles — used to help surgeons more easily locate the parathyroid glands so as not to remove them — or whose part of the parathyroids were reimplanted (typically in the forearm), a procedure called parathyroid autotransplantation.

The number of reimplanted parathyroid glands was also shown to impact recovery.

Patients who recovered parathyroid function within one month tended to have higher calcium and lower phosphorus levels. Calcium levels over 2.07 millimol/L and PTH concentrations greater than 1.2 picomol/L significantly associated with recovery  within six months post-surgery.

Overall, the study suggests that parathyroid function recovery may depend on calcium and PTH levels, and that patients should be prescribed calcium and calcitriol during the first month following a thyroidectomy.

“Permanent hypoparathyroidism should not be diagnosed easily by time after surgery,” the researchers concluded, “since up to one-fifth of the patients will recover beyond six months period and a few even after one year.”