IUDs Do Not Deliver Estrogen
No intrauterine device (IUD) currently available delivers estrogen—hormonal IUDs contain only levonorgestrel (a progestin), while copper IUDs contain no hormones at all. 1
Hormonal IUDs Contain Progestin Only
The levonorgestrel-releasing IUD is classified as a progestin-only contraceptive method with no estrogen component whatsoever, as confirmed by the American College of Obstetricians and Gynecologists. 1
The absence of estrogen in levonorgestrel IUDs makes them suitable for women with contraindications to estrogen, including those with cardiovascular risk factors, history of thromboembolism, antiphospholipid antibodies, or decompensated cirrhosis. 1
Available IUD Types in the United States
Levonorgestrel-releasing IUDs:
- 52 mg levonorgestrel IUD (Mirena): FDA-approved for 5 years but effective for up to 7-8 years 2, 1
- 52 mg levonorgestrel IUD (Liletta): approved for 3 years 2
- 13.5 mg levonorgestrel IUD (Skyla): approved for 3 years 2
Copper IUD:
- Copper T380-A (ParaGard): approved for 10 years but effective for at least 12 years, contains no hormones 2, 3
Mechanism of Levonorgestrel IUDs
The primary mechanism is preventing fertilization by inhibiting sperm motility and thickening cervical mucus, with all mechanisms occurring before implantation. 1
Levonorgestrel IUDs release only 20 micrograms of levonorgestrel daily locally into the uterus, resulting in very low systemic absorption. 4, 5
Estrogen Use with IUDs (Separate Administration)
If estrogen is needed for other indications (such as menopausal symptoms), it must be administered separately:
Transdermal estrogen patches can be combined with a levonorgestrel IUD for postmenopausal hormone replacement therapy, where the IUD provides endometrial protection against estrogen-induced proliferation. 6, 7
This combination involves separate devices: estrogen delivered through skin patches and progestin delivered through the IUD—they are not combined in a single device. 6, 7
The CDC guidelines note that for women using levonorgestrel IUDs who experience persistent bleeding, hormonal treatment with combined oral contraceptives or estrogen (10-20 days) can be added as a separate medication if medically eligible. 2
Clinical Implications
For breast cancer survivors and other women with contraindications to hormonal contraception, copper IUDs or barrier methods are recommended since exogenous hormonal contraception is generally contraindicated. 2
The levonorgestrel IUD's progestin-only formulation makes it an excellent option when estrogen must be avoided but effective contraception is needed. 1