Oxytocin: a neglected hormone in pituitary disease - From function to the diagnosis of a deficiency, resulting clinical relevance, and potential treatment options in endocrinology.

Oxytocin (OXT) is a neuropeptide hormone that plays a central role in numerous physiological and socio-emotional processes. Similar to arginine vasopressin (AVP), it is synthesized in the supraoptic and paraventricular hypothalamic nuclei and released both centrally and peripherally. Peripherally, OXT regulates uterine contractions during childbirth and milk ejection during lactation, metabolism, bone health, and cardiovascular functions. Centrally, it modulates social behavior, influencing trust, empathy, stress regulation, and emotional processing. Despite its close connection to AVP, the clinical significance of OXTDeficiency has only recently gained attention, particularly in patients with hypothalamic or pituitary damage with concomitant AVP-Deficiency. OXT-Deficiency may contribute to various neuropsychological symptoms seen in these patients, including social dysfunction, anxiety disorders, and reduced quality of life. However, a major challenge lies in accurately measuring OXT and thereby diagnosing a potential OXT-Deficiency. Basal plasma levels are unreliable, and most studied provocation tests only stimulate to a limited degree; hence, stronger provocation tests (e.g., using MDMA) and new surrogate parameters such as neurophysin I (NP-I) are gaining traction. Preliminary evidence from case reports and one small study suggests that intranasal OXT administration in patients with hypothalamic disorders may have beneficial effects on social behavior and emotion recognition. However, there is a clear need for larger, well-designed clinical trials, and several trials are currently underway to investigate the therapeutic potential of OXT in patients with AVP-Deficiency. OXT is also being explored as a possible treatment option in psychiatric conditions such as autism spectrum disorder, borderline personality disorder, and social anxiety disorder, with controversial results so far.