Considered one of the early pioneers of the field of neuroendocrinology,[1] she is best known for her work with Geoffrey Harris showing that the anterior pituitary gland is controlled by the hypothalamus via the hypophyseal portal system.
[2] There, she met Axel Westman at the Uppsala University Hospital, who permitted her to observe and assist in his endocrinological research on ovulation and reproduction in hypophysectomized (pituitary removed) animals.
[3][2] Although Jacobsohn was not permitted to do research as she was a foreigner without a Swedish degree, she worked with Westman at Lund University and ran clinical hormone assays for the hospital.
[3] In collaboration with Geoffrey Harris at Cambridge, Jacobsohn performed a series of elegant transplantation experiments, showing that pituitary grafts could only stimulate ovulation when in connection with the hypothalamus / mid brain, not the temporal lobe or other parts of the body.
She also did work showing that the posterior pituitary is required for milk ejection, later discovered to be mediated by the hormone oxytocin.