Can stopping progesterone (a hormone) 2 days ago cause an increase in resting heart rate (RHR) or tachycardia?

Effect of Progesterone Discontinuation on Resting Heart Rate

Stopping progesterone 2 days ago may cause an increase in resting heart rate due to the withdrawal of progesterone's cardiovascular effects, though evidence for this specific effect is limited. 1, 2, 3

Physiological Effects of Progesterone on Cardiovascular Function

• Progesterone has direct effects on the cardiovascular system, including modification of myofilament calcium sensitivity which can affect cardiac contraction 3
• In female mice, acute progesterone exposure has been shown to attenuate cardiac contraction and slow relaxation, suggesting its withdrawal could have opposite effects 3
• Progesterone can decrease forearm blood flow through increased vascular resistance, suggesting its withdrawal might lead to decreased vascular resistance and potentially increased heart rate 4

Hormonal Withdrawal Effects

• Withdrawal from high levels of progesterone has been associated with various physiological changes in animal models 5
• Progesterone withdrawal can affect central nervous system functioning, which might indirectly influence cardiovascular parameters including heart rate 6
• During pregnancy, progesterone contributes to cardiovascular adaptations including increased cardiac output and heart rate (15-20 bpm), suggesting its withdrawal could affect these parameters 1

Mechanisms That May Explain Heart Rate Changes

• Progesterone has been shown to affect the duration of cardiac action potentials, with one study showing that progesterone abbreviated action potential duration 3
• Progesterone can influence peripheral sympathetic tone, and its withdrawal may alter sympathetic nervous system activity affecting heart rate 4
• Studies have shown that progesterone can increase circulating norepinephrine concentrations, which could affect heart rate regulation 4

Clinical Considerations

• The effects of progesterone on cardiovascular function differ between males and females, with studies showing that progesterone's effects on cardiac contraction were only present in female mice 3
• Individual responses to progesterone withdrawal may vary based on factors such as age, underlying cardiovascular health, and concurrent medications 1
• The magnitude of heart rate changes after progesterone discontinuation would likely depend on the previous dosage and duration of progesterone therapy 1

Monitoring Recommendations

• Monitor for other symptoms that might accompany increased heart rate, such as dizziness or tiredness, which have been reported with changes in progesterone levels 6
• If increased heart rate persists or is accompanied by concerning symptoms (chest pain, severe dizziness, shortness of breath), medical evaluation is warranted 1
• Consider that other factors beyond progesterone withdrawal may contribute to increased resting heart rate, including stress, dehydration, or other medication changes 1

While the direct evidence linking progesterone discontinuation to increased resting heart rate is limited, the physiological effects of progesterone on cardiac function and vascular tone provide a plausible mechanism for this observation.