Background. The pituitary stalk (PS) is an anatomical structure consisting of the portal vessel system and axons of the hypothalamic nuclei terminating in the posterior pituitary lobe. Surgical injury or compression (by a tumor or another space-occupying process) of the PS can lead to hypopituitarism, diabetes insipidus, and hyperprolactinemia. However, the literature lacks studies on the extent of these disorders depending on PS injury or compression in clinical practice. Aim. The study aim was to investigate pre- and postoperative endocrine disorders in patients with chiasmo-sellar region (CSR) tumors and the PS compressed and preserved or involuntarily transected during neurosurgery. Material and methods. The PS compressed before surgery was preserved in 82 patients (41 patients with non-functioning endosuprasellar adenoma and 41 — with suprasellar meningioma). The PS was transected during transcranial surgery in 57 patients (46 patients with pituitary stalk craniopharyngioma and 11 patients with non-functioning endosupresellar pituitary adenoma). All patients underwent blood tests for prolactin (PRL), TSH, LH, FSH, free T4, cortisol, testosterone, or estradiol levels before and 6 months after surgery. Results. Hyperprolactinemia was detected in 37.4% of patients with CSR tumors compressing the PS. Elimination of PS compression led to normalization of the PRL level in most patients and was not accompanied by worsening of hypopituitarism symptoms. Transection of the PS resulted in panhypopituitarism in 100% of patients and diabetes insipidus in 93% of cases. There was no evidence of hyperprolactinemia in 58.7% of patients with craniopharyngiomas and 81.9% of patients with non-functioning pituitary adenomas. Conclusion. Given the difference in symptoms, we distinguished two syndromes: PS compression syndrome and PS transection syndrome. Syndrome of PS compression by a CSR tumor was characterized mainly by hyperprolactinemia (37.4% of cases); elimination of PS compression due to tumor resection led to normalization of the PRL level in most patients and was not accompanied by worsening of hypopituitarism symptoms. Syndrome of surgical PS transection in patients with craniopharyngioma (CP) and non-functioning pituitary adenoma (NFPA) manifested as panhypopituitarism in all patients and as permanent diabetes insipidus in most of them. The causes for the absence of hyperprolactinemia in many patients with the transected PS require further research. We can not exclude both adenohypophysis ischemia (due to its impaired blood supply) with partial or complete atrophy of lactotrophic cells and pituitary revascularization with restoration of dopamine transport.