The hormonal IUS (IntraUterine System), like the copper IUD, is a T-shaped device that is inserted (by a doc) into the uterus. Most people refer to it as a hormonal IUD. The difference is that there's no copper wiring; it has a reservoir of the progestin called levonorgestrel that gets released over time. Progestins are similar to the progesterone our bodies make but have different effects on the body.
Most commonly, the IUS contains 52 mg of levonorgestrel that it releases over the span of 5ish years: 20 mcg per day in the first while, reaching ~18 mcg by the end of year 1, and then ~10 mcg by the end of its lifespan. You can get IUSs with different dosages. The most common IUS is the Mirena. Other names you might've heard are Kyleena and Skyla.
Levonorgestrel basically creates an inhospitable environment for sperm as well as a fertilized egg: it thickens cervical mucus which prevents sperm from travelling to your eggs, and it thins out your uterine lining which impedes an egg from being implanted.
Light bleeding can be seen with this kind of IUS and some people completely lose their bleed.
You may or may not ovulate while on the hormonal IUS — some people stop ovulating especially in the first year or so but the number is close to 20% of users.
It's an effective contraception option, but it also helps decrease heavy menstrual bleeding and menstrual cramping.
There is a chance of conception and when conception happens, it has a higher likelihood of being ectopic than without an IUD/IUS. And there's an extremely slim chance that an IUD/IUS can cause uterine perforation.
Even though there is only a tiny bit of hormone being released each day, it does get into your systemic circulation which impacts some people more than others and may show up as hormonal symptoms like bloating, weight change, and feeling unwell. Always keep an eye on your symptoms and talk to your doc about your health changes.
