Menopausal hormone therapy increases the risk of gallstones: Health Insurance Database in South Korea (HISK)-based cohort study

Objective: To determine whether menopausal hormone therapy (MHT) increases the risk of gallstones and gallbladder cancer. Design: A retrospective cohort study. Patients or other participants: Data from the Korea National Health Insurance Corporation was obtained between January 1, 2002, and December 31, 2019. Interventions: Participants were divided into MHT and non-MHT groups; the MHT group was analyzed in detail by dividing participants into tibolone, combined estrogen plus progestin by the manufacturer (CEPM) or physician (CEPP), oral estrogen alone, and topical estrogen subgroups. Main outcome measures: The incidence of gallstones and gallbladder cancer was compared between the two groups. Results: This study enrolled 1,004,034 and 381,711 patients in the non-MHT and the MHT groups, respectively. The incidence of gallstones was 2.6% in the non-MHT group and 3.4%, 2.6%, 3.4%, 3.2%, and 4.4% in the tibolone, CEPM, oral estrogen alone, CEPP, and topical estrogen groups, respectively. Cox proportional hazard analysis revealed that all hormones increased the risk of gallstones ([tibolone] hazard ratio [HR]: 1.347, 95% confidence interval [CI]: 1.309–1.387, [CEPM] HR: 1.146, 95% CI: 1.1–1.19, [oral estrogen alone] HR: 1.241, 95% CI: 1.18–1.305, [CEPP] HR: 1.164, 95% CI: 1.01–1.341, [topical estrogen] HR: 1.602, 95% CI: 1.295–1.983). However, the risk of gallbladder cancer did not change with any hormone therapy. Conclusions: All types of MHT including tibolone, increased the risk of gallstones. This risk was the highest with topical estrogen, which may be a result of selection bias due to concerns regarding the adverse effects of CEE and MPA.