During the evaluation of secondary amenorrhea in a 24-year-old woman, hyperprolactinemia is diagnosed. Which of the following conditions could cause increased circulating prolactin concentration and amenorrhea in this patient?

In anorexia nervosa, prolactin, thyroid-stimulating hormone (TSH), and thyroxine levels are normal, FSH and LH levels are low, and cortisol levels are elevated. Prolactin is under the control of prolactin-inhibiting factor (PIF), which is produced in the hypothalamus. Many drugs (e.g., the phenothiazines), stress, hypothalamic lesions, stalk lesions, and stalk compression decrease PIF. In hypothyroidism, elevated TRH acts as a prolactin-releasing hormone to cause release of prolactin from the pituitary; hyperthyroidism is not associated with hyperprolactinemia. There are many other conditions, such as acromegaly and pregnancy, that are associated with elevated prolactin levels. Hyperandrogenic conditions such as congenital adrenal hyperplasia or polycystic ovarian disease are not typically associated with hyperprolactinemia.