Abstract Disclosure: F. Galbiati: None. J. Kang: None. D.J. Cote: None. J.E. Manson: None. U.B. Kaiser: None. Background: High prolactin (PRL) levels inhibit gonadotropin-releasing hormone (GnRH), causing hypogonadism. GnRH release is regulated by neurokinin B (NKB) and kisspeptin. NKB antagonists are used in treatment of menopausal hot flashes and vasomotor symptoms (VMS). In mice and humans with hyperprolactinemic anovulation, kisspeptin restored ovarian cyclicity and LH pulsatility. However, the interplay between kisspeptin and PRL is not fully understood. In two menopausal women with hyperprolactinemia and central hypogonadism, treatment with bromocriptine led to PRL normalization and new-onset VMS, suggesting that hyperprolactinemia inhibited VMS associated with hypogonadism. We aimed to investigate the association between PRL and menopausal VMS in women from the Nurses’ Health Study I and II (NHS, NHSII). We hypothesized that women with higher PRL levels would have a lower frequency/severity of menopausal VMS. Methods: We conducted a cohort study of 2618 females enrolled in NHS (n=1692) and NHSII (n=926) in whom blood samples were collected between 1989-99, were not pregnant or on hormonal therapy, and were either pre or post-menopausal as of blood draw. Subjects were free of breast, ovarian and other cancers, and provided complete data on VMS at menopause as well as in the past 4 weeks (assessed in 2008 in NHS and 2009, 2013, 2017 in NHSII). Plasma PRL was measured as part of 28 case-control studies of various health outcomes. We evaluated the presence and severity of VMS at menopause and 4 weeks prior to the questionnaire, as well as duration (in years) of VMS. We used multiple logistic regression, adjusting for covariates to estimate multivariable-adjusted relative risks (MVRRs) and 95% confidence intervals (CIs). Results: Women were aged 33-65 years at blood draw; range for years from blood draw to menopause was -10 to 10 (median=1.8) years; range for years from blood draw to report of VMS (both at menopause and current VMS) was 9.8 to 22 years. Mean PRL (SD; range) was 14.7ng/mL (10.1; 0.08-246). Women with the highest PRL levels were likely to be younger and less likely to be current smokers or obese. 77.4% of women reported VMS at menopause and 47.6% in recent 4 weeks; 52.3% reported moderate-to-severe VMS at menopause and 32.0% reported VMS in recent 4 weeks. Overall, PRL was not associated with duration of VMS or moderate-to-severe VMS at menopause or in the past 4 weeks; compared to the lowest quintile (≤8.0ng/mL), those in the highest PRL quintile (≥18.2ng/mL) had MVRR of 1.23(95%CI=0.94,1.60) for moderate-to-severe menopausal VMS and 1.03(95%CI=0.67,1.59) for recent VMS. Menopausal status did not affect the association between prolactin levels and VMS. Conclusion: PRL levels were not associated with occurrence, severity, or duration of menopausal VMS in a large cohort of women. Presentation: 6/1/2024