Endometrial hyperplasia
What is endometrial hyperplasia?
Endometrial hyperplasia is broadly defined as an excessive cellular proliferation leading to an increased volume of endometrial tissue. It is characterised by an increase in the endometrial gland-to-stroma ratio greater than 1:1.
Endometrial hyperplasia is further classified as simple or complex, with or without atypia. This classification system is based on the complexity and crowding of the glandular architecture.
The most common presenting symptom of endometrial hyperplasia is abnormal uterine bleeding, including:
Menorrhagia- Postmenopausal bleeding
- Intermenstrual bleeding
- Unscheduled bleeding on hormone replacement therapy
However, endometrial hyperplasia can also be asymptomatic and can spontaneously regress without being detected.
Histological classification of endometrial hyperplasia
Normal endometrium & Endo hyperplasia
Adapted from Palmer JE, et al. Obstet Gynecol 2008; 10:211-216.
Aetiology and risk factors
Oestrogen stimulates endometrial proliferation. A relative excess of oestrogen (exogenous or endogenous) compared with progesterone is considered to be one of the principle causes in endometrial hyperplasias.
Key risk factors in post-menopausal women include:
- Unopposed oestrogen
- Obesity, particularly in nulliparous women
Other risk factors include:
- Diabetes
- Hypertension
- Polycystic ovary syndrome
Incidence and diagnosis
Transvaginal ultrasound
Endometrial biopsy
Hysteroscopy
Efficacy and Safety
The efficacy of Mirena® in preventing oestrogen-induced hyperplasia in peri-menopausal and postmenopausal women has been assessed in various studies.
No hyperplasia was detected in any of the trials, regardless of dose, method of administration of oestrogen component or duration of therapy.
Mirena® significantly decreased menstrual bleeding compared with conventional oral hormone replacement therapy (P=0.001, N=200).
Continuing Mirena® use during the transition from contraception to ERT has no adverse effects on the vaginal bleeding profile.
The proportion of patients who had difficulties in coping with any items from the Women's Health Questionnaire decreased during both the contraception and ERT phases with Mirena®.
Prescribing Information: Mirena® (52 mg intrauterine delivery system Levonorgestrel)
PP-MIR-IE-0075-1 | February 2026