**Core Concept**
Polycystic Ovary Syndrome (PCOS) is a common endocrine disorder in women of reproductive age, characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries. The presence of subcapsular cysts on the ovary, raised free testosterone levels, and symptoms of oligomenorrhea along with hirsutism are suggestive of PCOS.

**Why the Correct Answer is Right**
The subcapsular cysts observed on the ovary are likely due to the accumulation of small follicles and stroma, which is a characteristic feature of PCOS. Elevated free testosterone levels contribute to the development of hirsutism, acne, and other androgenic symptoms. The combination of hyperandrogenism, ovulatory dysfunction, and polycystic ovaries is a classic triad for PCOS.

**Why Each Wrong Option is Incorrect**
**Option A:** Congenital Adrenal Hyperplasia (CAH) is a genetic disorder that leads to an overproduction of androgens due to enzyme deficiencies. However, it typically presents with ambiguous genitalia at birth and does not typically feature subcapsular cysts on the ovary.
**Option B:** Hyperprolactinemia can cause menstrual irregularities but is not typically associated with raised free testosterone levels or subcapsular cysts on the ovary.
**Option C:** Cushing's syndrome can lead to hyperandrogenism and menstrual irregularities, but it is usually associated with central obesity, hypertension, and other characteristic features that were not mentioned in the case.

**Clinical Pearl / High-Yield Fact**
PCOS is a heterogeneous disorder with a complex pathophysiology, and the diagnostic criteria have evolved over time. The Rotterdam criteria (2003) require the presence of at least two of the following three features: oligo- or anovulation, clinical and/or biochemical signs of hyperandrogenism, and polycystic ovaries on ultrasound.

**Correct Answer: D.**