Abstract
A transorbital, transsphenoidal microsurgical approach to the pituitary stalk and gland was used to collect blood from the hypothalamo-hypophyseal portal system in monkeys. Specimens may be obtained from the entire pituitary stalk, individual long portal veins, or the pituitary sinusoidal bed, with little risk of mortality. Continuous stalk blood sampling was carried out for periods of up to 10 hours. Pituitary sinusoidal-system blood was also collected during transsphenoidal surgery in man. The uses of data concerning hypothalamic-hypophyseal regulation obtained by these methods are illustrated.