Thyroid cancer tied to regular thyroxine use in hypothyroidism

(HealthDay)—Patients with primary hypothyroidism who are regular thyroxine users have increased risk of thyroid cancer, according to a study published online July 19 in the Journal of Clinical Pharmacology.

Shih-Han Hung, M.D., from Taipei Medical University Hospital in Taiwan, and colleagues conducted a case-control study to examine the correlation of thyroid cancer with primary hypothyroidism using data from the Taiwan Longitudinal Health Insurance Database 2005. Data were included for 1,285 patients with cancer and 3,855 sex- and age-matched controls.

The researchers identified a prior hypothyroidism diagnosis in 2.88 percent of cases and 0.86 percent of controls. Compared with controls, cases were more likely to have been previously diagnosed with hypothyroidism (adjusted odds ratio, 3.01). There was a significant association for thyroid cancer with hypothyroidism patients who were regular thyroxine users (adjusted odds ratio, 8.68). For hypothyroidism patients who were irregular thyroxine users, there was no significant association with thyroid cancer.

"Additional studies are needed to further evaluate and validate these findings," the authors write.