Does blocking progesterone change brain structure in people with PMDD?

Background: Premenstrual dysphoric disorder (PMDD) is a depressive disorder triggered by fluctuations of progesterone and estradiol during the luteal phase of the menstrual cycle. Selective progesterone receptor modulation (SPRM), while exerting an antagonistic effect on progesterone and maintaining estradiol on moderate levels, has shown beneficial effects on the mental symptoms of PMDD. Progesterone is also known for its neuroprotective effects, while synthetic progestins have been suggested to promote myelination. However, the impact of SPRM treatment on white matter microstructure is unexplored. Methods: Diffusion tensor imaging was employed to collect data on white matter integrity in patients with PMDD, before and after treatment with ulipristal acetate (an SPRM) or placebo, as part of a double-blind randomized controlled-trial. Tract based spatial statistics were performed to investigate SPRM treatment vs. placebo longitudinal effects on fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), on the whole white matter skeleton. Results: Voxel-wise analyses indicated no change over time in any white matter microstructure metrics in individuals treated with SPRM versus placebo. Improvement in PMDD symptoms did not correlate with changes in white matter microstructure. In secondary, exploratory, cross-sectional comparisons during treatment, the SPRM group displayed lower FA and higher MD, RD, and AD than the placebo group in several tracts. Conclusion: The main findings suggest that SPRM treatment did not impact white matter microstructure compared with placebo. However, secondary exploratory analyses yielded between-group differences after treatment, which call for further investigation on the tracts potentially impacted by progesterone antagonism. Clinical trial registration: EUDRA-CT 2016-001719-19; "Selective progesterone receptor modulators for treatment of premenstrual dysphoric disorder. A randomized, double-blind, placebo-controlled study."; https://www.clinicaltrialsregister.eu/ctr-search/trial/2016-001719-19/SE.

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