A 20-year-old nulliparous female college student sees the nurse because she has missed her last two menstrual periods. She reports she has not had sexual intercourse in one month. The nurse requests a pregnancy test, which is negative. Based on this client's history, which assessment is most important for the nurse to obtain?

A. While vaginal discharge, genital warts, and abdominal tenderness may indicate other concerns, they are not as directly related to menstrual irregularity without further investigation. B. Breast tenderness, tremors, and high blood pressure are less likely to be connected to missed periods in this context. C. Body weight changes, hirsutism, and thyroid enlargement could indicate thyroid dysfunction, such as hypothyroidism or polycystic ovary syndrome (PCOS), both of which can cause irregular periods. D. Urinary frequency, unsteady gait, and dental erosion are more indicative of a metabolic or neurological issue, which is less likely to explain missed periods.