Delayed sexual development in an adolescent female who is very thin may be associated with:

Rationale: A. Klinefelter syndrome affects males, leading to hypogonadism and delayed puberty, not females. B. Turner syndrome is associated with short stature and gonadal dysgenesis, but it is a chromosomal condition rather than related to body weight or nutrition. C. Anorexia nervosa can cause delayed sexual development in adolescent females due to malnutrition and low body fat, which disrupts hypothalamic-pituitary-ovarian axis function, leading to delayed puberty or amenorrhea. D. Hyperthyroidism generally accelerates metabolism and can sometimes cause early menarche or menstrual irregularities, but it is not typically associated with delayed sexual development.