A 22-year-old female came with the chief complaint of significant weight loss and secondary amenorrhea. She has a high-intensity exercise regimen, is preoccupied with food, and seems to have an irrational fear of gaining weight. Decreased production of which of the following hormones leads to amenorrhea in anorexia nervosa?

In Anorexia nervosa, the severe reduction in GnRH pulsatility leads to suppression of FSH and LH secretion, possibly to undetectable levels, and results in anovulation and low serum estradiol levels. Given the severe psychologic and metabolic stress experienced by these individuals, the hypothalamic-pituitary-adrenal axis is activated. The circadian rhythm of adrenal secretion is maintained, but both coisol production and plasma coisol levels are persistently elevated secondary to increased pituitary secretion of adrenocoicotropic hormone (ACTH). Serum leptin levels in these individuals are significantly lower than normal healthy controls and correlate with the percentage of body fat and body weight. A rise in leptin levels in response to dietary treatment is associated with a subsequent rise in gonadotropin levels.""Inhibition of reproduction function-- Enhanced release of the coicotrophin-releasing hormone (CRH) and b-endorphin suppresses GnRH release directly and indirectly through the release of glucocoicoids. Elevated glucocoicoids suppress the release of GnRH, luteinizing hormone, and follicle-stimulating hormone, and produce gonadotropin resistance at the gonads. This suppression in gonadal function is evident in patients with anorexia nervosa and extreme athletes."