Menstruation: Cycle Phases, Common Symptoms, and Menstrual Disorders

Introduction

Menstruation is the monthly shedding of the endometrial lining through the vagina, occurring as part of the menstrual cycle. The average cycle length is 28 days (range 21-35 days in adults), with menstruation lasting 3-7 days. The menstrual cycle is orchestrated by complex interactions between the hypothalamus, pituitary, ovaries, and endometrium.

Menstrual Cycle Phases

Ovarian Cycle

Phase	Days (28-day cycle)	Dominant Hormone	Ovarian Event
Follicular	Days 1-14 (variable)	FSH	Recruitment and maturation of ovarian follicles
Ovulation	Day 14 (day before to day after)	LH surge	Release of mature oocyte from dominant follicle
Luteal	Days 14-28	Progesterone	Corpus luteum formation and function

Uterine (Endometrial) Cycle

Phase	Days	Hormonal Driver	Endometrial Changes
Menstrual	Days 1-5	Estrogen and progesterone withdrawal	Shedding of functional endometrial layer
Proliferative	Days 6-14	Estrogen (from developing follicle)	Endometrial regeneration and proliferation; glands elongate
Secretory	Days 15-28	Progesterone (from corpus luteum)	Glandular secretion, stromal edema, vascularization; endometrium prepared for implantation

Hormonal Profile Throughout Cycle

Hormone	Early Follicular	Late Follicular	Ovulation	Mid-Luteal	Late Luteal
FSH	Moderate-high	Low-moderate	Sharp peak	Low	Low-moderate
LH	Low	Low-moderate	Massive peak	Low	Low
Estradiol	Low	Rising to peak	Peak (just before LH surge)	Moderate secondary peak	Falling
Progesterone	Low	Low	Low	High peak	Falling
Inhibin A	Low	Moderate	Rising	High	Falling
Inhibin B	Rising	High	Peak	Moderate	Low

Common Menstrual Symptoms

Premenstrual Syndrome (PMS)

Domain	Symptoms
Physical	Breast tenderness, bloating, fatigue, headache, joint/muscle pain, food cravings (especially sweets/salt), weight gain, acne
Emotional	Irritability, mood swings, anxiety, depression, crying spells
Behavioral	Social withdrawal, difficulty concentrating, sleep disturbance (insomnia or hypersomnia)
Onset	Symptoms appear 5-7 days before menses (luteal phase) and resolve within 4 days of onset of menses
Prevalence	50-80% of reproductive-age women experience some PMS symptoms; 20-30% have moderate-severe PMS

Premenstrual Dysphoric Disorder (PMDD)

Criterion	Description
A	Five or more symptoms present during the week before menses, improve within a few days of onset, and become minimal or absent in the week post-menses
B	At least ONE of: marked lability, marked irritability/anger, depressed mood/hopelessness, marked anxiety/tension
C	At least ONE additional: decreased interest in usual activities, difficulty concentrating, fatigue, appetite changes, sleep changes, feeling overwhelmed, physical symptoms (breast tenderness, bloating)
D	Symptoms cause clinically significant distress or functional impairment
E	Not exacerbation of another disorder
F	Symptom charting (prospective daily ratings) for at least 2 consecutive cycles
Prevalence	3-8% of reproductive-age women

Dysmenorrhea (Painful Periods)

Type	Cause	Onset	Duration	Associated Conditions
Primary	Prostaglandin-induced uterine contractions	Months to years after menarche	First 48-72 hours of menses	None
Secondary	Underlying pathology	Years after menarche (later onset)	Throughout menstruation; may extend before/after	Endometriosis, adenomyosis, fibroids, PID, cervical stenosis

Menstrual Disorders

Amenorrhea

Type	Definition	Common Causes
Primary	No menarche by age 15 (with secondary sexual characteristics) or by age 13 (without secondary sexual characteristics)	Turner syndrome, mullerian agenesis (MRKH), androgen insensitivity syndrome, constitutional delay
Secondary	Absence of menses for 3 months (with previously regular cycles) or 6 months (with previously irregular cycles)	Pregnancy (most common), hypothalamic amenorrhea (stress, weight loss, exercise), PCOS, hyperprolactinemia, premature ovarian insufficiency, thyroid disorders

Causes of Secondary Amenorrhea by Compartment

Compartment	Condition	Key Tests
Outflow tract	Asherman syndrome, cervical stenosis	Hysteroscopy, saline infusion sonography
Ovary	Premature ovarian insufficiency (POI), PCOS, ovarian tumor	FSH, AMH, estradiol, ultrasound
Pituitary	Prolactinoma, Sheehan syndrome, empty sella	Prolactin, MRI pituitary
Hypothalamus	Functional hypothalamic amenorrhea (stress, weight loss, exercise)	LH, FSH, estradiol (all low); rule out other causes
Other	Thyroid disease, adrenal disease, medications	TSH, DHEAS

Abnormal Uterine Bleeding (AUB) - PALM-COEIN Classification

Category	Acronym	Condition
Structural	P	Polyp (endometrial or endocervical)
Structural	A	Adenomyosis
Structural	L	Leiomyoma (fibroids): submucosal, intramural, subserosal
Structural	M	Malignancy and hyperplasia
Non-structural	C	Coagulopathy (von Willebrand disease, platelet disorders)
Non-structural	O	Ovulatory dysfunction (PCOS, thyroid, obesity, perimenopause)
Non-structural	E	Endometrial (primary endometrial dysfunction)
Non-structural	I	Iatrogenic (medications, IUD)
Non-structural	N	Not yet classified

Menorrhagia (Heavy Menstrual Bleeding)

Definition	Objective Criteria
Subjective complaint of heavy bleeding	Pictorial Blood Loss Assessment Chart (PBAC) score >100
Objective criteria	>80 mL blood loss per cycle
Duration	>7 days of bleeding
Impact	Anemia, iron deficiency, interference with quality of life
Quantitative signs	Clots >1 inch, soaking through pad/tampon every 1-2 hours, flooding, nocturnal bleeding

Oligomenorrhea and Polymenorrhea

Condition	Definition	Common Causes
Oligomenorrhea	Cycle length >35 days (infrequent menstruation)	PCOS, hypothalamic dysfunction, thyroid disease, perimenopause
Polymenorrhea	Cycle length <21 days (frequent menstruation)	Luteal phase defect, anovulation, thyroid disease

Menstrual Migraine

Type	Timing	Features
Pure menstrual migraine	Days -2 to +3 of menstrual cycle	No aura; longer duration; more refractory to treatment
Menstrually-related migraine	Perimenstrual + at other times	Similar features but also occurs outside menstrual window
Treatment	Perimenstrual prophylaxis (naproxen, triptans, estrogen supplementation)	Standard acute therapies; consider hormonal contraception for prevention

Perimenopause

Aspect	Details
Definition	Transition period from reproductive to menopausal years
Average age of onset	45-47 years
Duration	4-8 years (may be up to 10+ years)
Menstrual changes	Shortened cycles initially, then lengthened cycles, variable bleeding, skipped periods
Hormonal changes	Fluctuating FSH, declining inhibin B, variable estrogen (may be high or low)
Symptoms	Hot flashes (begin in late perimenopause), sleep disturbance, mood changes, vaginal dryness

Diagnosis of Menstrual Disorders

Initial Evaluation

Test	Rationale
Pregnancy test	Rule out pregnancy (urine or serum hCG)
CBC	Assess for anemia (iron deficiency)
TSH	Thyroid dysfunction
Prolactin	Hyperprolactinemia
FSH	Evaluate ovarian reserve/menopausal status
LH	Assess for PCOS (LH:FSH ratio >2)
Testosterone, DHEAS	PCOS, androgen excess
Pelvic ultrasound	Assess endometrial thickness, ovarian morphology, fibroids, polyps, adenomyosis

Management

Treatment of Dysmenorrhea

Therapy	Efficacy	Mechanism
NSAIDs (ibuprofen 400-600 mg q6h, naproxen 500 mg q12h)	High (first-line)	Inhibit prostaglandin synthesis
Acetaminophen	Moderate (less effective than NSAIDs)	Central analgesic effect
Heat therapy (heating pad, warm bath)	Moderate (adjunctive)	Increases pelvic blood flow, reduces cramping
Oral contraceptives (combined OCP)	High	Suppresses ovulation, reduces endometrial thickness
Levonorgestrel IUD (Mirena)	Very high	Progestin-mediated endometrial suppression
Exercise	Mild-moderate	Endorphin release, improved pelvic circulation
Dietary modification (reduce salt, caffeine)	Mild	Limited evidence

Treatment of Heavy Menstrual Bleeding

Therapy	Efficacy	Mechanism	Notes
Levonorgestrel IUD (Mirena)	High (80-90% reduction)	Local progestin	First-line for most patients
Tranexamic acid (Lysteda)	High (40-60% reduction)	Antifibrinolytic	Take only during menstruation
NSAIDs	Moderate (30-50% reduction)	Prostaglandin inhibition	Best if started day before or first day of menses
Combined OCP	Moderate	Endometrial suppression	Also provides contraception
Progestin-only (norethindrone 5 mg)	Moderate-high	Endometrial suppression	May use cyclic or continuous
Endometrial ablation	High (>90% reduction)	Destroys endometrial lining	For women not desiring fertility
Hysterectomy	Definitive	Removal of uterus	For severe cases, failed medical management

Treatment of Amenorrhea

Cause	Treatment
Pregnancy	Prenatal care
Hypothalamic (functional)	Weight restoration, reduce exercise, stress management; may need hormonal therapy for bone protection
PCOS	Weight loss, metformin, OCPs for cycle regulation, ovulation induction if desiring pregnancy
Premature ovarian insufficiency	Hormone replacement therapy (HRT) for bone and cardiovascular health; donor egg for fertility
Hyperprolactinemia	Dopamine agonist (cabergoline, bromocriptine)
Thyroid disease	Thyroid hormone replacement (hypothyroidism) or antithyroid medication (hyperthyroidism)
Asherman syndrome	Hysteroscopic adhesiolysis