MON-198 Reduced Brown Adipose Tissue Activity Across the Menopausal Transition: Assessing the Effects of Endogenous and Exogenous Sex Steroids

Abstract Disclosure: A.D. De Jesus: None. A. Joham: None. S. Hutchison: None. M.A. Cowley: None. B.A. Henry: None. Introduction: Brown adipose tissue (BAT) activity is higher in females than males and is thought to decline with age. During mid-life, women are at greater risk of developing central obesity and cardiometabolic disease. The role of altered BAT function in the metabolic health of post-menopausal women remains unknown. The aim of this study was to characterise changes in BAT activity and glucose tolerance across the menopausal transition. We sought to determine whether altered BAT activity was associated with declining ovarian sex steroids or increased follicle-stimulating hormone (FSH). Finally, we assessed whether combined menopausal hormone therapy (MHT) altered BAT activity in post-menopausal women. Methods:Pre- (ages 18-39y/o, luteal phase), peri- (ages 40-49y/o), and post-menopausal (non-MHT and MHT users; ages 50-60y/o) women were recruited (n=9-12/group). Peri-menopausal women exhibited two or more of the following: Irregular menstrual cyclicity, increased incidence of hot flushes or sweating at night. Post-menopausal women had undergone the final menstrual period (FMP; >12 months since last menses). Participants were fasted overnight, and resting energy expenditure (REE) was determined via indirect calorimetry. Weight, height, BMI, waist circumference and fat mass were assessed. Infrared thermography was used to measure cutaneous supraclavicular temperature as an index of BAT temperature in response to either cold exposure (15oC) or an oral glucose tolerance test (75g). Continuous glucose monitors measured transcutaneous glucose concentrations. A single blood sample was collected to measure 17β-estradiol, progesterone, FSH, and insulin concentrations. Results: Resting energy expenditure was significantly lower in post-menopausal compared to pre-menopausal women (p<0.01). Post-menopausal women had lower 17β-estradiol levels compared to the pre- (p<0.01) and peri-menopausal women (p<0.001). Progesterone (p<0.001) and FSH (p<0.0001) were elevated in the peri-menopausal group. In response to both cold and glucose, BAT heat production was attenuated in both peri-and post-menopausal women compared to pre-menopausal women (p<0.0001). This suggests that the decline in BAT function occurred prior to the menopause-associated changes in 17β-estradiol, progesterone or FSH concentration. BAT activity was also similar in MHT and non-MHT post-menopausal women, indicating that MHT does not alter BAT activity. Finally, the attenuated BAT response did not coincide with impaired glucose tolerance in peri- and post-menopausal women. Conclusion: Our findings suggest that BAT activity is impaired in women across the menopausal transition, however this is not associated with any major change in reproductive hormones. Further work is required to elucidate the mechanisms that underpin impaired BAT activity in peri and post-menopausal women. Presentation: Monday, July 14, 2025