**Core Concept**
Heavy menstrual bleeding (HMB) in adolescents is a common concern that warrants a thorough evaluation. The differential diagnosis includes anovulatory cycles, polycystic ovary syndrome (PCOS), thyroid disorders, bleeding disorders, and anatomical abnormalities. A comprehensive approach is essential to identify the underlying cause.

**Why the Correct Answer is Right**
Estradiol levels are not typically indicated in the evaluation of heavy menstrual bleeding in adolescents. This is because estradiol levels can be affected by various factors, including the timing of the menstrual cycle and the use of hormonal contraceptives. Moreover, estradiol levels are not a reliable marker for diagnosing conditions that cause HMB. An evaluation for HMB in adolescents would focus on identifying anovulatory cycles, which can be assessed through a combination of physical examination, medical history, and other investigations.

**Why Each Wrong Option is Incorrect**
**Option A:** TSH is an important investigation to rule out thyroid disorders, which can cause heavy menstrual bleeding. Thyroid disorders, such as hypothyroidism, can lead to changes in menstrual patterns and are a common cause of HMB in adolescents.
**Option B:** Platelet count is essential to evaluate bleeding disorders, such as von Willebrand disease, which can cause heavy menstrual bleeding. A low platelet count can indicate a bleeding disorder that requires further investigation and management.
**Option C:** Bleeding and clotting time are important investigations to rule out bleeding disorders, such as hemophilia or von Willebrand disease. These tests can help identify abnormalities in coagulation that may be contributing to heavy menstrual bleeding.

**Clinical Pearl / High-Yield Fact**
In adolescents with heavy menstrual bleeding, it is essential to consider the possibility of anovulatory cycles, which can be caused by PCOS, thyroid disorders, or other endocrine abnormalities. A thorough evaluation, including physical examination, medical history, and appropriate investigations, is necessary to identify the underlying cause and develop an effective treatment plan.

**✓ Correct Answer:** D. Estradiol levels.