The interplay of central insulin and menstrual cycle on functional brain networks and neural food cue reactivity in women.

The menstrual cycle impacts food intake, peripheral metabolism, and brain function. One well-known central regulator of eating behavior is the hormone insulin. Here, we show that the responsiveness of functional brain networks to central insulin varies dynamically across the menstrual cycle in premenopausal women. Intranasal insulin (INI) administration increases functional connectivity within networks that support decision-making processes (namely the default mode and salience network) in the follicular compared to the luteal phase of the menstrual cycle. In contrast, INI decreases functional connectivity within the somatosensory network during the follicular phase relative to the luteal phase. In response to visual food cues, hippocampus and dorsal striatum activity are higher in the luteal compared to the follicular phase, particularly to sweet food. Estradiol and progesterone levels predict these changes. This could contribute to higher food craving and food intake observed in the luteal phase. Our findings emphasize sex hormones' role in modulating brain sensitivity to hormonal signals and external stimuli.