LAUSR

Dear Editor, I found the discussion and proposals made by Manyonda et al. very interesting, particularly their consideration of the potential for using Estrogen-only Replacement Therapy (ERT) with an Levonorgestrel Intrauterine Device (LNG-IUD) to avoid the risks and side effects associated with progestogens used in Combined Hormone Replacement Therapy (cHRT). However, the author’s concern with this option was that ‘progestogen permeates into the blood stream’ which may have an impact on breast cancer risk. They reported little research surrounding this, and the available studies referenced mainly examined premenopausal women. A paper published by Buckner in 2019 examined the extent to which progestogens were seen in the plasma and cervical mucus, given the method of delivery. It showed that, with an LNG-IUD in situ, plasma concentrations were less than 1% of that found in cervical mucus. This compares to plasma concentrations being over 2000% of that found in the cervical mucus when progestogens are administered systemically. This study suggests that an LNG-IUD could achieve the same endometrial protection with incomparably smaller plasma progestogen concentrations. Buckner’s data confirms that some progestogen does permeate into the blood stream whilst using an LNG-IUD, and therefore the breast cancer risk would not be zero. However, it is important to acknowledge that this could be a significant reduction in risk compared to the alternative option of cHRT (with an increased risk of 24%). Information from studies such as this may alleviate the worries of the authors regarding the magnitude of the risk associated with using an LNG-IUD. Contributorship