Increased risk of thyroid cancer among women with hysterectomies.

Abstract

Hysterectomy with bilateral oophorectomy has been suggested to increase the risk of thyroid cancer. We studied the relationship between hysterectomy and thyroid cancer in a population-based setting in Finland. Women undergoing hysterectomy between 1986 and 1995 (n = 17,900) were identified from the National Hospital Discharge Registry. The cohort was followed up through the Finnish Cancer Registry until 1997. There were 118 cases of thyroid cancer diagnosed, 103 papillary and 15 follicular or medullar type. The incidence for thyroid cancer was significantly elevated (standardized incidence ratio [SIR] 1.38, 95% CI 1.15-1.64). The increase in the incidence of thyroid cancer was not dependent on the extent of operation but on the length of follow-up. Thyroid cancer incidence was increased 0.5 to 1.4 years after hysterectomy (SIR 2.00, 95% CI 1.31-2.93), but decreased thereafter (SIR 1.30, 95% CI 0.99-1.67). Hysterectomy with and without oophorectomy was associated with a similar increase in the incidence of thyroid cancer. Women who have undergone hysterectomy have an increased risk of thyroid cancer during the first 2 years after the operation. Thyroid cancer and bleeding disorders may share a common background.