Hydrogen magnetic resonance spectroscopy (1HMRS) is nowadays one of the basic tools for noninvasive brain metabolism assessment. The study focuses on the important problem of the influence of hormone fluctuation during the menstrual cycle on brain metabolism, assessed by 1HMRS for clinical diagnostics.

In 11 healthy regularly menstruating women, 1HMRS was performed at the start (phase I), in the middle (phase II) and at the end (phase III) of the menstrual cycle. The relative concentration ratios of 12 brain metabolites in every woman in all cycle phases were examined, in 6 different volumes of interest (VOIs). Finally, statistically significant differences in relative metabolite ratios between the phases examined in given locations were sought.

Statistically significant relations between menstrual cycle phases and relative ratios of 4 metabolites – Lac/Cr, NAA/Cr, Glx1/Cr and Glx2/Cr – in different brain locations were found. In all locations, mean NAA/Cr ratios were greater in phase I compared to the other phases. A similar relationship was found for Glx1/Cr ratio in one location (left occipital lobe). For Lac/Cr and Glx2/Cr ratios, a higher mean ratio value was obtained in phase II compared to phases I and III in the right occipital lobe and left basal ganglia, respectively.

Menstrual cycle phase should be considered in planning a date and interpretation of 1HMRS examination, performed for the verification of a disease manifesting as brain metabolite disturbances in the 1HMRS spectrum.