**Core Concept**
Polycystic Ovary Syndrome (PCOS) is a complex endocrine disorder characterized by ovulatory dysfunction, hyperandrogenism, and polycystic ovaries. Sex hormone-binding globulin (SHBG) is a protein that binds to androgens and estrogens, influencing their availability and activity in the body.

**Why the Correct Answer is Right**
In PCOS, the levels of SHBG are typically low. This decrease in SHBG levels results in an increase in free androgen index, as more androgens are available to bind to androgen receptors. The low SHBG levels in PCOS are due to insulin resistance, which is a hallmark of the disorder. Insulin resistance leads to increased production of insulin, which in turn suppresses the production of SHBG by the liver. This decrease in SHBG levels contributes to the hyperandrogenism seen in PCOS.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because SHBG levels are typically low in PCOS, not high. High SHBG levels would be seen in conditions such as hypogonadism or hyperthyroidism.
**Option B:** This option is incorrect because SHBG levels are not directly affected by the presence of polycystic ovaries. Polycystic ovaries are a morphological characteristic of PCOS, but they do not directly influence SHBG levels.
**Option C:** This option is incorrect because SHBG levels are not a diagnostic criterion for PCOS. While low SHBG levels are seen in PCOS, they are not unique to this disorder and can be seen in other conditions as well.

**Clinical Pearl / High-Yield Fact**
Low SHBG levels in PCOS are a reflection of insulin resistance and contribute to the development of hyperandrogenism. This is a key clinical correlation that can help in the diagnosis and management of PCOS.

**Correct Answer: D. Low levels of sex hormone-binding globulin are seen in PCOS.**