Objective: 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.
Study design: 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.
Results: 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.
Conclusion: 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.