**Core Concept**
Premature ovarian failure (POF) is a condition characterized by the cessation of ovarian function and decreased estrogen production before the age of 40, leading to elevated follicle-stimulating hormone (FSH) levels and decreased estradiol levels.

**Why the Correct Answer is Right**
The patient's presentation of amenorrhea and biochemical investigations showing increased FSH and decreased estradiol levels are indicative of premature ovarian failure. In this condition, the ovaries stop functioning, leading to a decrease in estradiol production and an increase in FSH levels as the body attempts to stimulate the ovaries. The elevated FSH levels are a hallmark of POF, as the pituitary gland produces more FSH in an attempt to stimulate the ovaries to produce eggs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
Premature ovarian failure can be caused by various factors, including genetic mutations, autoimmune disorders, chemotherapy, and radiation therapy. It is essential to investigate the underlying cause of POF to guide management and provide appropriate counseling to the patient.

**Correct Answer:** C. Premature ovarian failure.