The purpose of this study is to compare left ventricular stroke volume and heart rate responses to bursts of SNA between PMF using, and not using, MHT.

Inclusion Criteria

• >45-60< years of age

Exclusion Criteria

• Male sex
• Females between STRAW+10 stages -5 and 0
• PMF in STRAW+10 stage +2
• PMF using oral hormone therapy
• Females who entered menopause due to a surgical procedure or in response to pharmacotherapy (e.g., gonadotrophin releasing hormone agonists or chemotherapy)
• Heart disease such as hypertropic cardiomyopathy, congenital abnormalities, chronic heart failure, valve disease, and a history of myocardial infarction
• Medications that impact the central nervous system including selective serotonin reuptake inhibitors, anxiolytics, sedatives, anticholinergic agents, dopamine, amphetamines, or wake-promoting agents (e.g., modafinil). Other medications will be evaluated on an individual basis by the PI.
• Cardiovascular medications is also an exclusion criterion which includes those acting on the renin-angiotensin-aldosterone axis, adrenergic receptor antagonists, diuretics, nitrates, and calcium channel antagonists. Other medications will be evaluated on an individual basis by the PI.
• Pregnancy
• COPD
• Diabetes
• CKD
• Raynaud's phenomenon
• Sleep disorders
• Shift workers
• BMI ≥40.0kg/m2
• Use of nicotine-containing products within the two years preceding study visits
• Active cancer treatment

Study participants will be recruited from various Mayo Clinic departments/clinics located at Rochester and surrounding communities.