Plasma and urinary catecholamines during the human ovulatory cycle.

Area of Science:

• Endocrinology
• Neuroscience
• Reproductive Biology

Background:

• Plasma catecholamines, such as norepinephrine, are key indicators of sympathetic neural activity.
• Understanding physiological variations in catecholamine levels is crucial for accurate interpretation in disease states.
• The ovulatory cycle involves significant hormonal shifts that may influence autonomic nervous system function.

Purpose of the Study:

• To investigate the relationship between the ovulatory cycle and plasma catecholamine concentrations.
• To determine if sympathetic neural activity, as measured by norepinephrine, exhibits cyclic patterns.
• To assess urinary catecholamine excretion in parallel with plasma levels during the menstrual cycle.

Main Methods:

• Measurement of plasma catecholamine concentrations (norepinephrine) in six healthy women.
• Collection and analysis of urinary catecholamine excretion throughout the ovulatory cycle.
• Comparison of catecholamine levels between the follicular and luteal phases.

Main Results:

• Plasma norepinephrine concentrations were significantly lower during the follicular phase compared to the luteal phase (143 vs. 217 pg/ml, p < 0.001).
• Norepinephrine levels began to rise approximately two days before ovulation and remained elevated post-ovulation.
• Urinary norepinephrine excretion demonstrated a similar, albeit less pronounced, cyclic pattern.

Conclusions:

• Sympathetic neural activity, indicated by plasma norepinephrine, undergoes significant changes during the ovulatory cycle.
• The cyclic fluctuation of norepinephrine suggests hormonal influences on the sympathetic nervous system.
• Cyclic variations in plasma norepinephrine must be considered when using it as a biomarker for sympathetic activity in various health conditions.