A 34-year-old woman presents to her physician complaining of palpitations, weight loss despite increased appetite, heat intolerance, and mild tremor. Laboratory studies reveal elevated serum free T3 and T4 levels with undetectable TSH. To investigate the mechanism of TSH suppression by elevated thyroid hormones, researchers infuse exogenous T3 into healthy volunteers and measure changes in hypothalamic and pituitary function. Which of the following best describes the primary mechanism by which T3 suppresses TSH secretion?