What is an LNG (Levonorgestrel) IUD, and is it a hormonal treatment?

What is an LNG-IUD?

The LNG-IUD (levonorgestrel intrauterine device) is a hormonal contraceptive device that releases the progestin hormone levonorgestrel directly into the uterine cavity. 1

Hormonal Mechanism

• Yes, the LNG-IUD is definitively a hormonal contraceptive that releases levonorgestrel, a synthetic progestin hormone, at approximately 20 µg per 24 hours for at least 5 years 2
• The hormone acts primarily locally within the uterus rather than systemically, meaning blood levels of levonorgestrel remain much lower compared to oral progestin-only pills 3
• The local hormonal effect causes marked suppression and thinning of the endometrial lining, making it unresponsive to ovarian estrogen 4, 5

How It Works

The LNG-IUD provides contraception through multiple mechanisms:

• Primary mechanism: Strong antiproliferative action on the endometrium that prevents implantation 5
• Thickening of cervical mucus that blocks sperm penetration 5
• Minimal effect on ovulation—most women continue to have normal ovarian function and ovulate regularly 2

Contraceptive Effectiveness

• Extremely effective contraception with a Pearl pregnancy rate of 0.0-0.2 per 100 woman-years over 5-7 years of use 6
• The cumulative gross pregnancy rate after 5 years is only 0.5 per 100 women 2
• Unlike copper IUDs, the LNG-IUD maintains the same low pregnancy rate across all age groups 6
• Provides protection against ectopic pregnancy with a rate of only 0.02 per 100 woman-years 6, 2

Therapeutic Benefits Beyond Contraception

The LNG-IUD offers significant non-contraceptive health benefits:

• Reduces menstrual blood loss by more than 90% within the first year of use, making it highly effective for treating heavy menstrual bleeding (menorrhagia) 4, 6
• Improves body iron stores and increases hemoglobin concentration by reducing blood loss 4
• Eliminates dysmenorrhea (painful periods) in most users 6
• Reduces risk of pelvic inflammatory disease 5, 2
• Can be used for endometrial protection during hormone replacement therapy 4, 3
• CDC classifies it as first-line treatment for heavy menstrual bleeding, particularly in patients with cardiovascular risk factors 7

Expected Bleeding Pattern Changes

All women will experience changes in their bleeding pattern after insertion:

• Irregular spotting and light bleeding are common during the first 2-3 months after insertion 6, 3
• Progressive reduction in menstrual blood loss occurs over time 5
• After 6 months, approximately 20% of women become amenorrheic (no periods) 3
• After 5 years, about 50% of women have no menstrual bleeding at all 3
• This amenorrhea is not due to hormonal dysfunction but rather the local endometrial suppression, and is considered a positive therapeutic effect 3

Insertion Requirements and Timing

• Can be inserted anytime if reasonably certain the patient is not pregnant 1
• Requires bimanual examination and cervical inspection before insertion 1
• If inserted more than 7 days after menses started, backup contraception (abstinence or condoms) is needed for 7 days 1
• Most patients do not require additional STI screening at time of placement unless they have risk factors and haven't been screened per CDC guidelines 1

Common Side Effects

• Hormonal side effects can occur but are less common than with systemic hormonal contraceptives: mood changes, oily skin, and acne 5
• Weight gain is similar to copper IUDs: approximately 500 grams per year over 5 years 5
• The main side effect is irregular breakthrough bleeding, most common in the first 6 months—detailed counseling about expected bleeding changes is crucial to prevent unnecessary discontinuation 3

Reversibility

• Fertility returns quickly after removal 6, 2
• No difference in return of fertility compared to copper IUDs 2