In a normal menstrual cycle, GnRH (gonadotropin-releasing hormone) is released in a slow and pulsatile manner, regulating the pituitary hormones FSH and LH. FSH is responsible for growing the follicles that house the eggs in the ovary, while LH is responsible for the timing of ovulation.
LH and FSH have a regulatory effect on the ovary and thus on the release of the sex hormones estrogen and progesterone. In turn, the sex hormones have negative feedback on GnRH, thus closing the regulatory cycle.
All hormones must work within a concentration range where they are functional; if their concentrations are both above and below this range, fertility can be accepted. When hormones increase in concentration, negative feedback kicks in to bring them back to their corresponding values.
In a woman with elevated stress levels, elevated blood concentrations of cortisol (the stress hormone) have been seen. Elevated concentrations of stress hormone interact by altering the frequency of GnRH pulses. The direct effect of cortisol on GnRH, which causes an increase in its secretion, produces the alteration of the rest of the hormones of the hypothalamus-pituitary-ovary axis and produces reproductive problems.
Overexposure to GnRH can trigger negative feedback regulatory processes to lower it, however, in a woman with this mechanism altered by cortisol, it can produce an abrupt drop in GnRH. This drop can cause those hormones that are over-stimulated to drop to levels below the range considered normal, producing alterations in menstruation.