What is Levonorgestrel-Releasing Intrauterine System (LNG-IUS)?

Levonorgestrel-Releasing Intrauterine System (LNG-IUS)

The Levonorgestrel-Releasing Intrauterine System (LNG-IUS) is a long-acting, reversible contraceptive device that releases levonorgestrel directly into the uterine cavity, providing highly effective contraception while offering significant therapeutic benefits including reduced menstrual bleeding and pain relief. 1, 2

Mechanism and Description

• LNG-IUS consists of a T-shaped device with a silastic reservoir containing levonorgestrel attached to the vertical arm, covered by a rate-limiting silastic membrane 3
• It releases approximately 20 μg of levonorgestrel per 24 hours directly into the uterine cavity for at least 5 years 3
• The local release of levonorgestrel causes strong uniform suppression of the endometrial epithelium, making it insensitive to estradiol from the ovaries 2
• The primary contraceptive mechanism occurs at the endometrial level through decidualization, epithelial atrophy, and direct vascular changes 4

Contraceptive Efficacy

• LNG-IUS is one of the most effective forms of contraception available with 5-year failure rates of only 0.5-1.1 per 100 users 2
• The Pearl index after 5 years is 0.09/100 woman-years, with an ectopic pregnancy rate of 0.02/100 woman-years 3
• Efficacy is comparable to female sterilization but with complete reversibility 5
• Equally effective across all age groups and not affected by the user's body weight 2

Therapeutic Benefits

• Significant reduction in menstrual blood loss and number of bleeding days, making it suitable for treatment of menorrhagia 2, 6
• Progressive reduction in menstrual blood loss continues over time, with many women experiencing amenorrhea after 9 months of use 6
• Relief from dysmenorrhea (painful menstruation) and premenstrual symptoms 2
• Provides endometrial protection during hormone replacement therapy 2, 4
• Effective in preventing endometrial proliferation associated with estradiol therapy 5
• Can induce regression of endometrial hyperplasia 5

Bleeding Patterns

• Initial months often characterized by irregular, scanty bleeding that typically resolves spontaneously 2
• After 6 months, approximately 20% of women become amenorrheic, increasing to 50% after 5 years 4
• Despite amenorrhea, most women continue to ovulate normally 2, 6
• All possible patterns of bleeding can be seen among users 2

Medical Eligibility

• The CDC classifies LNG-IUS as Category 1 (no restriction) or Category 2 (benefits generally outweigh risks) for most conditions 1
• Recommended as first-line treatment for heavy menstrual bleeding in patients with cardiovascular risk factors 7
• Can be used in women with endometriosis (Category 1) 1
• Safe for use in women with ovarian cancer who undergo fertility-sparing treatment (Category 1) 1
• Can be used in women with uterine fibroids (Category 2) unless there is uterine distortion 1

Side Effects and Considerations

• Main side effect is irregular breakthrough bleeding, most common in first 6 months after insertion 4
• Some women may experience hormonal side effects such as mood changes, oily skin, and acne 6
• Weight increase is similar to copper IUDs at approximately 500g per year over 5 years 6
• Does not protect against sexually transmitted infections; condoms should be used by women at risk 6

Patient Counseling

• Detailed counseling about expected changes in bleeding patterns is crucial to improve continuation rates 2, 4
• Women should be informed that amenorrhea is a benign effect resulting from local action on the endometrium, not disruption of normal ovarian function 6, 4
• User satisfaction is strongly associated with information provided at the time of insertion 2
• Good pre-insertion counseling significantly reduces the risk of premature removal 2

The LNG-IUS represents an excellent option for women seeking both contraception and therapeutic benefits for menstrual disorders, combining high efficacy with minimal systemic effects and significant quality of life improvements 2, 5.