Hi, A routine thickened endometrial lining reading on ultrasound in the presence of fibroids typically indicates that there is an increased amount of tissue in the lining of the uterus. This can be caused by a variety of factors, including hormonal imbalances, certain medications, and medical conditions such as endometrial hyperplasia or cancer. However, in the presence of fibroids, it is more likely due to the effect of the fibroids on the uterus. Fibroids are noncancerous growths that can develop in or on the uterus. Depending on their location, size, and number, they can cause a range of symptoms, including heavy or painful periods, pelvic pain or pressure, and in some cases, infertility. Fibroids can also cause the uterus to enlarge and distort, which can lead to a thickened endometrial lining on ultrasound. The uterus responds in this way to fibroids because they can disrupt the normal architecture of the uterine wall, which can lead to overgrowth of the endometrium. Additionally, fibroids can cause abnormal uterine bleeding, which can further contribute to thickening of the endometrium. It is not uncommon for women with fibroids to have a thickened endometrial lining on ultrasound, regardless of their age. However, it is important to note that a thickened endometrial lining can also be a sign of more serious conditions, such as endometrial cancer. Therefore, it is important to follow up with a healthcare provider if you have any concerns or symptoms related to your reproductive health. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician