What is the luteal phase of menstruation in a female patient of reproductive age?

What is the Luteal Phase of Menstruation?

The luteal phase is the second major phase of the menstrual cycle that begins immediately after ovulation and ends either with the onset of menstruation or establishment of pregnancy, typically lasting approximately 14 days. 1, 2

Timing and Duration

• The luteal phase starts following ovulation, which occurs after a sharp increase in luteinizing hormone (LH), estrogen, and follicle-stimulating hormone (FSH) levels during the preceding follicular phase 3, 1
• In a standard 28-day cycle, ovulation typically occurs around days 12-14, with the luteal phase comprising the remaining days until menstruation 1
• The normal luteal phase length averages 14.13 ± 1.41 days, with most women falling within this range 2
• Luteal phases of 9 days or less are considered abnormal, and approximately 5.2% of cycles demonstrate a short luteal phase 2

Hormonal Characteristics

During the luteal phase, estrogen and progesterone levels progressively increase until the mid-luteal phase (approximately 6-8 days after ovulation), when their levels start to slowly decline. 3, 4

• The corpus luteum (the structure formed from the ovulated follicle) secretes progesterone, estradiol, and inhibin A in response to LH pulses 4
• Progesterone concentrations rise sharply after ovulation, reaching a peak approximately 8 days after the LH surge 5
• The corpus luteum reaches its peak in terms of size, secretions, and vascularization 6-7 days after ovulation 4
• If pregnancy does not occur, progesterone and estrogen levels decline in the late luteal phase, triggering menstruation 3, 1

Physiological Functions

Primary Reproductive Function

• The luteal phase prepares the uterus for embryo implantation through progesterone-mediated endometrial changes, a function known as uterine receptivity 6
• The corpus luteum's hormonal secretions are essential for establishing and maintaining early pregnancy 6

Metabolic Effects

• High estrogen levels during the luteal phase improve glucose metabolism by increasing glucose availability and glycogen storage in skeletal muscle 3, 1
• Estrogen increases the availability of free fatty acids and enhances oxidative energy metabolism 1
• Protein requirements may be higher during the luteal phase due to increased progesterone-driven protein catabolism 1

Respiratory and Cardiovascular Effects

• The luteal phase is characterized by increased ventilatory drive 3, 1
• Despite these physiological changes, menstrual phase generally does not significantly influence exercise performance at low altitudes 3, 1

Clinical Significance

Luteal Phase Deficiency

• Luteal phase deficiency (LPD) occurs when the corpus luteum's secretory activity is insufficient or when the endometrium responds inadequately to normal progesterone levels 6
• LPD can lead to problems with endometrial receptivity, dysfunction of the local uterine immune system, increased risk of embryo rejection, abnormally high uterine contractility, and restriction of uterine blood flow 6

Assessment of Ovulation

• Measurement of mid-luteal phase progesterone levels (blood taken during the mid-luteal phase according to menstrual cycle timing) can indicate whether ovulation has occurred 3
• Progesterone levels less than 6 nmol/L suggest anovulation, with common causes including polycystic ovary syndrome (PCOS), hypophyseal adenoma, or hyperprolactinemia 3

Symptom Development

• The luteal phase hormonal fluctuations, particularly the withdrawal of estrogen and progesterone, may trigger premenstrual symptoms in vulnerable women 7
• Individual differences in the kinetics of progesterone decline (sharp vs. gradual) may influence susceptibility to premenstrual syndrome, independent of absolute hormone concentrations 8