FFinalistSouthampton · 2027
Obstetrics & gynaecology
AKT · Obstetrics & gynaecology/Contraceptionlow yield

Levonorgestrel IUS (Mirena)

Intrauterine levonorgestrel — LARC; endometrial thinning

Overview

A progestogen-releasing intrauterine device (LARC, 5–8 years depending on brand) that thins the endometrium and thickens cervical mucus. Doubles as treatment for heavy menstrual bleeding and as the progestogen component of HRT — periods usually become light or absent.

Recognise

  • LARC; very effective; local progestogen with minimal systemic effect
  • Periods become lighter or stop (vs the copper coil which makes them heavier)
  • Licensed for heavy menstrual bleeding and for endometrial protection in HRT
  • Small risk of uterine perforation at fitting and expulsion

Red flags

  • Current breast cancer (UKMEC 4); active pelvic infection/undiagnosed bleeding before fitting

Differentials & how to tell them apart

Copper IUDnon-hormonal coil — makes periods HEAVIER, and is the most effective emergency contraception
Contraceptive implantsubdermal LARC; does not thin the endometrium or treat HMB
Endometrial ablationa surgical HMB option — the IUS is the first-line medical/LARC option for HMB

Investigations

STI risk assessment before fitting; exclude pregnancy and undiagnosed abnormal bleeding; bimanual to assess uterus.

Management

LNG-IUS — contraception that also treats heavy menstrual bleeding / protects endometrium in HRT

  1. 1Offer as LARC, especially if periods are heavy. Assess STI risk, exclude pregnancy/undiagnosed bleeding, then fit.Gate: Undiagnosed abnormal vaginal bleeding must be investigated BEFORE fitting an IUS/IUD
  2. 2Persistent pain/abnormal bleeding after fitting → exclude perforation, expulsion, malposition, infection.
Levonorgestrel intrauterine system — 5–8 years; also first-line for heavy menstrual bleeding

Key points

The first-line medical treatment for heavy menstrual bleeding doubles as contraception. Provides the progestogen arm of HRT (endometrial protection).

Monitor & prognosis

Threads check; bleeding pattern; replace at licensed interval.

Rapidly reversible on removal.

Source: FSRH UKMEC 2016; NICE NG88 (heavy menstrual bleeding)