T2D risk elevated in thyroid cancer patients after thyroidectomy

Development of type 2 diabetes (T2D) is more likely to occur among patients with thyroid cancer who underwent thyroidectomy than matched controls, a Korea study has shown. In addition, a U-shaped dose-dependent relationship exists between the levothyroxine dosage and T2D risk.

Using the Korean National Health Insurance database, the investigators conducted a retrospective population-based cohort study and determined whether thyroidectomy increased the risk of T2D in patients with thyroid cancer and to explore the association between levothyroxine dosage and T2D risk.

A total of 36,377 thyroid cancer patients without known diabetes who underwent thyroidectomy between 2004 and 2013 were included in the study. They were matched with nonthyroid cancer patients using 1:1 propensity score matching. New-onset T2D was the main outcome measure.

Patients with thyroid cancer who underwent thyroidectomy were at greater risk of developing T2D than matched controls (hazard ratio [HR], 1.43, 95 percent confidence interval [CI], 1.39‒1.47).

In the thyroid cancer patient group, the risk of T2D increased in the first quartile (<101 μg/day; HR, 1.45, 95 percent CI, 1.36‒1.54) and fourth quartile groups (≥150 μg/day; HR, 1.37, 95 percent CI, 1.29‒1.45) when the second quartile group was considered as reference (in terms of the mean levothyroxine dosage; 101‒127 μg/day).

On the other hand, T2D risk decreased in the third quartile group (128‒149 μg/day; HR, 0.91, 95 percent CI, 0.85-0.97).

“Abnormal thyroid function after thyroidectomy and subsequent thyroid-stimulating hormone suppression can have detrimental effects on glucose homeostasis in patients with thyroid cancer,” the investigators said.