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    Lorentz Center Highlights

Mary Lou Zeeman

Bowdoin College, mathematics Department, Bruinswick, USA

"Rhythms in the Pituitary"

ABSTRACT: Neuroendocrine control of the menstrual cycle involves three-way feedback interactions between the ovaries, the hypothalamus and the pituitary. Briefly: over the course of each cycle, the hypothalamus stimulates the pituitary to release hormones to the ovaries, where the egg matures, releasing increasing levels of estradiol. This, in turn, initiates a sudden surge of luteinizing hormone (the LH surge) from the pituitary, triggering ovulation. The precise mechanism by which estradiol initiates the LH surge has remained elusive, in part because hypothalamus-pituitary interactions are not well understood. We use a simple forced oscillator model to explore the possibility that the pituitary has an intrinsic rhythm, and that the LH surge arises when rhythms of the hypothalamus and pituitary come into transient resonance. We then describe recent 3-d imaging work revealing beautiful new levels of organization and rhythm within the pituitary.