The Menstruating Years

The menstrual cycle is a vital sign.

It’s how we make hormones, and this provides short and long term health benefits. Each cycle is like an investment in the peri/menopausal years, when you stop making these hormones.

During pregnancy, the menstrual cycle pauses and your body makes estrogen and progesterone in higher amounts. Breastfeeding temporarily pauses the cycle hormones.

the menstrual life cycle depicts the relationship between estrogen and progesterone throughout the lifespan

The Menstrual Life Cycle

graph depicting the relationship between the ovarian hormones and brain signals

The menstrual cycle is a series of hormonal events that represent communication between the brain and the reproductive system

the result of these hormonal changes is the physical event of ovulation, the release of the egg

the two halves of the menstrual cycle are called the follicular and luteal phase

each menstrual cycle begins with the menstrual bleed, cycle day 1

during the follicular phase, estrogen is rising

the menstrual cycle wheel shows the distinct phases of follicular and luteal, plus shows the time of menstruation and the time of the fertile window culminating with ovulation

pregnancy is only possible during the fertile window, the 6 days leading up to and including ovulation

ovulation divides the two phases

testosterone is highest around ovulation

after ovulation, during the luteal phase, the body makes progesterone

during the menstrual phase, the cervix opens to let blood flow during menstruation

The Four Phases of The Menstrual Cycle

during the follicular phase follicle development occurs, early proliferative phase of the uterine lining, and cervical fluid production begins
during the ovulatory phase, ovulation occurs, it is the late proliferative phase of the uterine lining, and cervical fluid production peaks
during the luteal phase the corpus luteum forms, the uterine lining is in its secretory phase, and the cervix is closed

Ovulation Begins In The Brain

  • The communication between the brain and the ovaries is called the Hypothalamus-Pituitary-Ovarian-Axis

  • The process begins in the hypothalamus, where gonadotropin releasing hormone (GnRH) stimulates the anterior pituitary gland

  • The pituitary releases a hormone called follicle stimulating hormone, or FSH, causing FSH levels to rise.

shows the hormonal feedback loops between the brain and the ovaries that regulate the menstrual cycle

The Ovarian Cycle

cycle of ovarian development from follicle recruitment, follicle development, ovulation, luteal formation, and luteal regression

  • High levels of FSH tell the developing ovarian follicles to secrete estrogen

  • Estrogen rising makes FSH levels fall

  • Back in the brain, low FSH tells the hypothalamus - pituitary to release luteinizing hormone (LH)

  • LH causes the mature follicle to burst open & the egg is released! This is ovulation.

  • After ovulation, the follicle (fluid sac that held the egg) inverts on itself, creating the corpus luteum, releasing progesterone

  • Progesterone inhibits FSH & LH - telling the HPA to stop releasing them & preventing the event of ovulation from occurring again in the same cycle

  • 2 weeks later, If the egg is unfertilized, the corpus luteum degenerates, progesterone falls, and the menstrual cycle concludes with the bleed.

The Uterine Cycle

the uterine cycle is comprised of the menstrual, proliferative, and secretory phases

  • The uterine lining (endometrium) undergoes major changes during the cycle

  • The uterine cycle has 3 phases

  • Menstrual: The menstrual bleed is the detachment of the uterine lining

  • Proliferative: Each cycle you make new lining when estrogen starts to rise. The uterine glands start out small and sporadic looking, growing thicker and the glands becoming more coiled as estrogen peaks

  • Secretory: At ovulation and afterwards as progesterone rises, the glands become more coiled and the lining reaches its maximum thickness. This creates the ideal environment for a fertilized egg to implant into, which is necessary for pregnancy

Putting It All Together

shows the menstrual cycle in terms of ovarian development, ovarian hormones, basal body temperature, cervical fluid, cervical position, and uterine lining development


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