Endometrial Hyperplasia

Endometrial hyperplasia is a condition characterized by abnormal thickening of the endometrium (the lining of the uterus) due to prolonged exposure to estrogen without adequate progesterone. It is a common gynecologic condition and is considered a precancerous state in certain forms, particularly when cellular atypia is present.

The condition most often occurs in women with hormonal imbalance — especially those experiencing anovulation, perimenopause, or obesity. Because progesterone normally counteracts estrogen’s proliferative effects on the endometrium, insufficient progesterone leads to continuous endometrial growth, increasing the risk of abnormal bleeding and, in some cases, progression to endometrial cancer.

Early identification and appropriate management are critical, as many cases are reversible, while others require closer surveillance or definitive treatment.

How the Endometrium Normally Functions

In a normal menstrual cycle:

Estrogen stimulates growth (proliferation) of the endometrial lining during the follicular phase
Ovulation occurs
Progesterone is produced by the corpus luteum, stabilizing and differentiating the endometrium
If pregnancy does not occur, progesterone falls, leading to shedding of the lining (menstruation)

Endometrial hyperplasia develops when:

Estrogen stimulation is unopposed by progesterone
The endometrium continues to proliferate without normal shedding or regulation

Types of Endometrial Hyperplasia

Classification is based on the presence or absence of cellular atypia:

Type	Characteristics	Clinical significance
Without atypia	Glandular overgrowth without abnormal cells	Lower risk of progression to cancer
With atypia (atypical hyperplasia / EIN)	Cellular abnormalities present	High risk of progression to endometrial cancer

Atypical hyperplasia is considered a direct precursor to endometrial carcinoma and requires more aggressive management.

Causes and Risk Factors

Unopposed estrogen exposure (primary driver)

The central mechanism is prolonged estrogen stimulation without progesterone.

Common causes include:

Anovulation (most common)
Polycystic ovary syndrome (PCOS)
Perimenopause (irregular ovulation)
Estrogen-only hormone therapy (without progesterone in women with a uterus)

Metabolic and systemic factors

Obesity — adipose tissue increases estrogen production via aromatization
Insulin resistance — contributes to hormonal imbalance
Diabetes and metabolic syndrome

Reproductive and hormonal factors

Early menarche / late menopause
Nulliparity
Infertility
Chronic irregular menstrual cycles

Medications and conditions

Tamoxifen (selective estrogen receptor modulator with uterine effects)
Estrogen-secreting tumors (rare)

Symptoms and Clinical Presentation

The most common presenting feature is abnormal uterine bleeding:

Heavy menstrual bleeding
Prolonged periods
Irregular cycles
Intermenstrual bleeding
Postmenopausal bleeding (always requires evaluation)

Some women may be asymptomatic, with hyperplasia detected incidentally on imaging.

Diagnostic Evaluation

Transvaginal ultrasound

Measures endometrial thickness
Thickened endometrium raises suspicion, particularly in postmenopausal women

Endometrial biopsy (definitive diagnosis)

Required to confirm diagnosis and determine presence of atypia
Histological evaluation distinguishes between benign hyperplasia and precancerous changes

Additional evaluation

Hysteroscopy — direct visualization of uterine cavity
Assessment of underlying hormonal or metabolic causes

Hormonal and Laboratory Evaluation

Identifying the underlying cause is essential for management.

Core hormonal markers

Marker	What it assesses	Clinical relevance
Estradiol (E2)	Estrogen levels	May be elevated or relatively unopposed
Progesterone	Ovulation status	Low levels suggest anovulation
LH / FSH	Ovulatory function	Helps identify PCOS or ovarian dysfunction

Additional markers

Marker	Role
TSH	Thyroid dysfunction can contribute to cycle irregularity
Prolactin	Elevated levels suppress ovulation
Fasting insulin / glucose	Assess insulin resistance
Lipid panel	Metabolic risk assessment

Key Endocrine Drivers

Anovulation

The most common cause of endometrial hyperplasia. Without ovulation, progesterone is not produced, leading to continuous estrogen stimulation.

Obesity and insulin resistance

Excess adipose tissue increases estrogen production, while insulin resistance disrupts ovulatory function — creating a dual mechanism for unopposed estrogen exposure.

Perimenopause

Irregular ovulation during the transition to menopause leads to fluctuating estrogen levels and insufficient progesterone, increasing risk.

When to Seek Evaluation

Abnormal uterine bleeding at any age
Postmenopausal bleeding
Irregular or heavy cycles
Known risk factors (PCOS, obesity, chronic anovulation)
Infertility with irregular cycles

Treatment Overview

Treatment depends on the presence of atypia and patient-specific factors.

Without atypia

Progesterone therapy (oral, injectable, or intrauterine device)
Weight loss and metabolic optimization
Treatment of underlying endocrine disorders
Regular monitoring with repeat biopsy if needed

With atypia (precancerous)

Definitive treatment: hysterectomy (standard recommendation in many cases)
Fertility-sparing option: high-dose progesterone therapy with close monitoring in selected patients

Addressing underlying causes

Ovulation induction in anovulatory women
Management of insulin resistance (e.g., lifestyle, medications)
Adjustment of hormone therapy

Prognosis

Hyperplasia without atypia has a low risk of progression and is often reversible with treatment
Hyperplasia with atypia carries a significant risk of progression to endometrial cancer if untreated
Early detection and appropriate management lead to excellent outcomes in most cases

Summary

Endometrial hyperplasia is a hormonally driven condition characterized by abnormal thickening of the uterine lining due to unopposed estrogen exposure. It most commonly arises in the setting of anovulation, obesity, and hormonal imbalance.

The condition ranges from benign, reversible forms to precancerous atypical hyperplasia with significant malignant potential. Diagnosis is confirmed through endometrial biopsy, while hormonal and metabolic evaluation helps identify the underlying cause.

Treatment is highly effective and focuses on restoring hormonal balance — particularly through progesterone therapy — or surgical management in higher-risk cases. Early evaluation of abnormal bleeding is essential to prevent progression and ensure optimal outcomes.