This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraceptives, Subject name: Gynaecology & Obstetrics
Mirena releases ____ of LNG per day. 
Select and explain. 
A. 20 mg, B. 20 microgram, C. 52 mg, D. 52 microgram
B: 20 microgram
Answer: B: 20 microgram 
Explanation: Mirena contains a total of 52 mg levonorgestrel (LNG). LNG is released into the uterine cavity at a rate of approximately 20 microgram/day. The LNG IUD is about as effective as sterilization, but, unlike sterilization, it is easily reversible. These devices act mainly by local progestogenic effects and act for up to 5 years.