The effect of hormone therapy on physiological uptake of the endometrium on [18F]F-FDG PET in postmenopausal women

Objective The effects of hormonal therapy, estrogen-based hormone replacement therapy (HRT), and anti-tumor hormone therapy, such as tamoxifen, on the physiological uptake of the endometrium on 2-deoxy-2[ 18 F]fluoro- d -glucose ([ 18 F]F-FDG) positron emission tomography (PET) in postmenopausal women have not been determined. We explored the effect of hormone therapy, particularly HRT, on physiological uptake in the endometrium of postmenopausal women. Materials and methods Postmenopausal women receiving hormone therapy who underwent cancer screening using PET/computed tomography (CT) between June 2016 and April 2023 were included in the hormone therapy group ( n = 21). Postmenopausal women with no history of hormone therapy were included in the control group ( n = 49). First, the physiological endometrial uptake at menopausal age and at least 1 year thereafter was compared quantitatively (SUVmax) and qualitatively (4-point scale) in the control group, to assess when the endometrium ceased to show significant physiological [ 18 F]F-FDG uptake after menopause. Endometrial uptake was compared between the hormone therapy and control groups. The association between HRT duration (months) and endometrial uptake (SUVmax) was evaluated. Endometrial thickness, measured using transvaginal ultrasonography, was also compared between the two groups. Results Endometrial uptake was significantly reduced both qualitatively and quantitatively ( P