Final answer:
The most common cause of abnormal uterine bleeding in adolescents in the first few years after menarche is anovulatory cycles due to the maturing reproductive system. Hormonal imbalances during this time can cause the endometrium to shed irregularly. It's important for individuals experiencing excessive or painful bleeding to seek medical evaluation.
Step-by-step explanation:
The most common cause of abnormal uterine bleeding in adolescents during the first 1-2 years after menarche is anovulatory cycles. During this time, the reproductive system is still maturing, and hormonal regulation may not be fully established, leading to the absence of ovulation in certain menstrual cycles. This lack of ovulation can result in an imbalance between estrogen and progesterone, causing the endometrium to thicken and subsequently shed irregularly, manifesting as abnormal uterine bleeding or menorrhagia.
As adolescents transition from the onset of menarche to more regular menstrual cycles, these anovulatory cycles tend to become less frequent. However, if menstrual irregularities continue or if bleeding is excessively heavy or painful, it is essential for the individual to seek medical advice to rule out underlying conditions such as thyroid disorders, bleeding disorders, or other reproductive system pathologies.
Aside from anovulatory cycles, another potential cause of abnormal bleeding could be reproductive system disorders such as endometriosis, but these are less common in the initial post-menarche years. It is critical to note that any episode of abnormal uterine bleeding that raises concern should be evaluated by a healthcare provider to determine the appropriate investigation and management.