Abnormal thyrotropin and prolactin levels in untreated corticotropin deficiency.

A patient with isolated corticotropin deficiency demonstrated hyperresponsiveness of both thyrotropin and prolactin after protirelin stimulation. Following glucocorticoid replacement therapy, responses decreased to normal. Since true primary hypothyroidism may occur in association with cortisol-deficient states, it is necessary to reserve final evaluation until after glucocorticoid replacement. The finding of combined thyrotropin and prolactin hyperresponsiveness to protirelin suggests a related glucocorticoid feedback function.