An evaluation of dynamic pituitary function tests in patients with pituitary tumours

In a prospective study of 26 patients with macroadenoma of the pituitary (14 secretory and 12 non-secretory), basal and stimulated pituitary hormone levels were used to detect hypothalamic dysfunction and to examine pituitary hormone secretion before and after hypophysectomy. Suprasellar tumour extention with hypothalamic compression occurred in 18 patients but was not consistently associated with hormonal tests indicative of hypothalamic dysfunction. In patients with secretory tumours, secretory activity was adequately assessed by basal hormone levels alone, which showed that surgery reduced hormone levels by a mean 85% in acromegaly and by a mean 55% in prolactinomas. Preoperatively, pituitary reserve of hormones not being hypersecreted was often normal, despite large tumour size and hypothalamic compression. Even after apparently complete pituitary removal at surgery, normal responses to stimulatory tests could sometimes be detected. Conventional dynamic tests are only of limited value in the assessment of hypothalamo-pituitary dysfunction in patients with large pituitary tumours and should not be used indiscriminately in such individuals requiring surgery.