Changes in energy expenditure during the menstrual cycle

Area of Science:

• Reproductive Endocrinology
• Human Metabolism
• Chronobiology

Background:

• The menstrual cycle influences various physiological processes.
• Understanding metabolic fluctuations during the menstrual cycle is crucial for women's health.

Purpose of the Study:

• To investigate cyclical changes in metabolic rate throughout the menstrual cycle.
• To determine if hormonal fluctuations correlate with metabolic rate variations.

Main Methods:

• Eight women were monitored under metabolic-ward conditions.
• Whole-body calorimetry was performed at four distinct menstrual cycle phases.
• Hormone levels (salivary and urinary) and body temperature were tracked.

Main Results:

• Sleeping metabolic rate exhibited cyclical changes, peaking in the late luteal phase (6.1% increase).
• 24-hour energy expenditure showed a non-significant increase.
• No significant changes in thyroid hormones or urinary reproductive hormones explained the metabolic rate variations.

Conclusions:

• Metabolic rate during sleep fluctuates cyclically across the menstrual cycle.
• These metabolic changes are not explained by significant alterations in thyroid hormones or key reproductive hormones.