Depypere HT, Stanczyk FZ, Croubels S, et al. - Women using an LNG-IUS were examined for breast tissue and serum LNG concentrations. In this pilot study of 25 healthy women undergoing breast surgery at the Ghent University hospital, women using the LNG-IUS showed a very low concentration of LNG in breast epithelium cells. The 18 LNG-IUS users had a mean LNG concentration of 0.18±0.16 ng/mL in serum and 0.26±0.28 ng/g in breast tissue. The mean concentrations were below the limit of quantification in four women without any form of hormonal contraceptive (the negative controls). For the three positive controls, the concentrations in the serum (20.5 and 3.4 ng/ml) and the breast (3.74 and 1.24 ng/g) were respectively for the 20 μg EE/100 μg users and 315 pg/ml in the serum and 1.17 ng/g in the breast for the minipill user.