What is the typical hallmark sign of polycystic ovary syndrome (PCOS)?

The hallmark sign of polycystic ovary syndrome (PCOS) is irregular menses. This condition is characterized by hormonal imbalances, and one of the most common manifestations is an irregular menstrual cycle. Women with PCOS may experience prolonged cycles, skipped periods, or unusually heavy or light menstrual bleeding. This irregularity is often due to the presence of insulin resistance and elevated levels of androgens, which can disrupt the normal hormonal regulation of the menstrual cycle.

While pelvic pain, infertility, and abnormal hair growth are associated with PCOS, they are not considered the primary or hallmark sign. Pelvic pain might occur in some women, but it is more commonly linked to other conditions such as endometriosis. Infertility can result from the ovulatory dysfunction seen in PCOS, but it is a consequence rather than a defining feature. Abnormal hair growth, or hirsutism, is another common symptom due to elevated androgen levels, yet it is also not specific enough to be considered the hallmark sign.

Irregular menses is the most consistent and definitive symptom that can lead to a diagnosis of PCOS, making it the best choice among the options provided.