Menarche

Adrenarche

The awakening of the adrenal gland

• Begins around age 8

• Increase in adrenal androgen production (male sex hormones)

  • DHEAS/androstenedione

  • Increased body odor, oiliness in the skin, appearance of pubic and axillary hair

Gonadarche

Gonads begin to mature and produce sex hormones

• Begins around age 8

• Hypothalamus produces GnRH → signals pituitary gland to release LH and FSH → LH and FSH stimulate gonads to grow and produce sex hormones

Thelarche

Development of breast buds

Pubarche

• Onset of growth of pubic hair

• Axillary hair

Growth Spurt

• Acceleration in growth rate due to GnRH and insulin-like growth factor 1 (somatomedin C)

Menarche General

First menstrual period

• Occurs between ages 9 and 15: usually 2 years after thelarche

• Average age is 12-12.5

• Average height is 4’11” - 5’2”

• Average weight is 99-110 lbs

Critical body weight is important

• Body’s fat content must account for 17% of the body’s weight before menarche can occur

• At age 18, the fat content must be at least 22% for the maintenance of regular menstrual cycles

Chronological Order of Female Pubertal Events

• Adrenarche (8 y/o)

• Gonadarche (8 y/o)

• Thelarche-Breast bud (9-10 y/o)

• Pubarche-onset pubic hair (11-12 y/o)

• Maximal growth spurt (11-12 y/o)

• Menarche (11.5-12.8 y/o)

• Adult pubic hair-13.7 y/o

• Adult breast-14.6 y/o

Hormones

• Estrogen, progesterone, LH, FSH

  • See a marked increase in menarche

• Other factors

  • Fat:lean ratio

  • Nutrition

  • Underlying disease

• Higher fat levels associated with increased estrogen production (fat cells contain aromatase, an enzyme that converts androgens into estrogens)

  • Increase fat → increases aromatization androgens → estrogen → (+) feedback to hypothalamus/pituitary → LH surge (needed for ovulation)

Clinical Effects of Hormones on Menarche (6)

• Increased vaginal secretions

• Reduced vaginal pH

• Vaginal mucosa thickens and becomes rugated, cornification

• Labia protrudes, thickens, rugated

• Uterus increases in size and length

• Mean weight of ovaries increases

Menstrual Cycle General

Onset 9-14 y/o

• Typically occurs at Tanner stage IV breast development

• Rare before Tanner III development

Normal Menstruation

• Duration: 3-5 days

• Menstrual blood mostly arterial (spiral arteries) (25% venous)

• Contains tissue debris, prostaglandins, large amounts of fibrinolysin from endometrial tissue

  • Fibrinolysin lyses clots in menstrual blood to dissolve clots and maintain normal blood flow

• Average blood loss: 30 mL

Early Cycles and Transition to Regular Ovulation

• Tend to be irregular at onset and perimenopause

• At least 50% of menstrual cycles anovulatory in the first year but in fairly regular intervals

  • Having irregular cycles → most likely anovulatory

• During first 2 years after menarche → cycles somewhat irregular but 90% will have cycles within range of 21-42 days with 2-8 days of flow

• By the 7th year of menarche → 90% cycles ovulatory

  • Once ovulatory, may experience dysmenorrhea

Oligomenorrhea Definition

• Infrequent menstruation: > 35 days

Polymenorrhea Definition

• Frequent menstruation: < 21 days

Dysmenorrhea Definition

• Painful menstruation

Menorrhalgia Definition

• Dysmenorrhea, painful menses

Menorrhagia Definition

• Excess/prolonged uterine bleed but at regular intervals

Metorrhagia Definition

• Irregular bleeding

• Uterine bleeding at times other than expected menses

Menometorrhagia Definition

• Excessive uterine bleeding both during menses and at irregular intervals

Uterine and Ovarian Cycle

Shed off menses → start building lining back up

Follicular (Proliferative) Phase

• First day of menses until ovulation

  • Variable in length

• Characteristics

  • Low basal body temperature

  • Development of ovarian follicles

  • Vascular growth of endometrium

  • Secretion of estrogen from ovary

  • Uterine cramps from prostaglandins

Luteal (Secretory) Phase

• Ovulation until onset of menses

• Under influence of progesterone: want progesterone to be the highest in the middle of the luteal phase to ensure that it is aiding in the development of pregnancy

• Constant in duration (12-16 days: mean 14 days)

• Characteristics

  • Elevated basal body temperature

  • Corpus luteum forms

  • Endometrial changes

  • Decreased sexual desire and sexual enjoyment

GnRH

• Hypothalamic hormone that controls gonadotropins

  • Stimulates synthesis and release FSH and LH

  • Continuous exposure of GnRH inhibits FSH and LH

• Secreted in pulsatile manner: amplitude/frequency variable

• Regulated by estrogen/progesterone feedback

Estrogen Production

• Ovarian follicle has 2 key cell types: both of these regulate estrogen production and follicular development

  • Granulosa cell receptors

  • Theca cell receptors

• LH acts on theca cells to promote biosynthesis of androgens → androgens diffuse to neighboring granulosa cells where aromatase enzyme complex converts them to estrogen under the influence of FSH

Granulosa Cell Receptors

• FSH receptors

• Functions

  • Promotes follicular growth

  • Converts androgens into estrogen

• In late stage follicles: LH receptors which help prepare the follicle for ovulation and triggers progesterone production

Theca Cell Receptors

• LH receptors

• Stimulates androstenedione production

• Provides androgens to granulosa cells for estrogen synthesis

Progesterone

• Depends on LH/FSH

• Functions

  • Implantation of oocyte into endometrium

  • Sustain pregnancy early in 1st trimester

• Produce 24 hours prior to ovulation and lasts for 11 days

• Without fertilization: decrease progesterone and decrease FSH/LH

Cycles Diagram

• Like to wait for patients to come in at the end of their cycle if they have heavy bleeding → should have a thin lining

  • A thick lining would mean something abnormal

Oogenesis

• Many oocytes (around 12) but usually only one matures before ovulation → others become atretic

• The oocytes mature until the follicle containing one of them reaches an average of 18-25 mm diameter and then breaks open → releases oocyte into abdomen (ovulation) and the rest become atretic

• Pain from this ovulation → Mittelschmerz

Progression of Follicles

• Primordial follicle → seen with anovulation

• Pre-antral follicle → most become atretic (do not become mature)

• Antral follicle → dominant cell secretes estrogen → decrease FSH → atresia

• Pre-ovulatory follicle

Follicular Changes in Menstrual Cycle Picture

Ovulation

• Ovulation 28-36 hours after LH begins to rise and then 8-20 hours after LH peak

  • Occasional spotting at ovulation caused by changes in estrogen levels

• LH surge most reliable indicator of ovulation

• LH surge

  • Completes division of oocyte

  • Luteinization of granulosa cells

  • Synthesis of progesterone and prostaglandins (rupture of follicle wall)

Multiple Ovulation

• Double ovulation → releasing 2 eggs within 24 hour window

  • Fraternal twins

• Superfetation → ovulation at different times

  • Extremely rare, but a second ovulation can occur days or weeks later in the same cycle

  • Can lead to a second pregnancy at a different developmental stage

• Sperm can survive 5-7 days, so if ovulation occurs at slightly different times, fertilization can happen days apart

Corpus Luteum

• Forms from cells that surrounded oocyte

  • Maintained 13-14 days unless pregnant

  • Progesterone peaks 8-9 days post ovulation

• When pregnant, corpus luteum produces progesterone for several weeks until placenta can take over

  • Maintained by hCG early in pregnancy

• Defective luteal phase → infertility/spontaneous abortion

  • Do not have enough progesterone to maintain endometrial lining for successful implantation

  • Reason for giving someone progesterone the second half of their cycle to help get pregnant

Menstruation

• Without pregnancy → decrease steroids → constriction of spiral arteries → ischemia and breakdown of endometrium → bleeding

• Corpus luteum becomes corpus albicans

• Endometrial lining regenerates and cycle begins all over again

Cycle Changes in the Endometrium