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Neuroendocrinology and Pituitary

SUN-003 - Utility of the Cosyntropin Stimulation Test in the Diagnosis of Oxytocin Deficiency

Sunday, June 14, 2026
9:00 AM - 4:00 PM CT
Location: ENDOExpo; Poster Floor
Disclosure(s):
Ilan Remba, MD: No financial relationships to disclose
Karen K. Miller, MD: No relevant disclosure to display
Francesca Galbiati, MD: No financial relationships to disclose
Background
Individuals with arginine vasopressin deficiency (AVP-D) are at risk for oxytocin (OXT) deficiency (OXT-D), a newly described syndrome characterized by worse neuropsychiatric and bone health. Diagnosis of OXT-D is challenging due to OXT’s short half-life, pulsatile release, and overlapping basal levels between deficient and healthy groups. There is a need for a safe and reliable provocative test to diagnose OXT-D. Cosyntropin stimulation is commonly used to assess adrenal insufficiency, and hypothalamic-pituitary-adrenal (HPA) stimulation increases OXT levels in animal models. To evaluate the cosyntropin stimulation test as a candidate assessment for OXT-D, we investigated whether levels of plasma OXT and neurophysin I (NP-I), a more stable biomarker co-secreted with OXT in equimolar concentrations, increase in response to cosyntropin.

Methods
We collected plasma at baseline and 5,15, 30, and 60 minutes after administration of 250 mcg IV cosyntropin in patients undergoing clinically indicated cosyntropin stimulation testing. Unextracted OXT and NP-I levels were measured in duplicate with Arbor and Abcam ELISA assays (inter-, intra-assay coefficient of variation: OXT, 1.9, 8.9%; NP-I, 8.4, 7.9%). Wilcoxon Signed-Rank test was used to compare OXT and NP-I levels at each time point from baseline.

Results
Fifteen patients (10 female, mean±SD age 51±18 years, body mass index 29.9±5.5 kg/m2) participated in the study. Reasons for adrenal insufficiency evaluation included: post-surgery and/or radiation for sellar lesion (10), untreated sellar lesion (2), exogenous steroids (2), and hypophysitis (1). No participants had AVP-D. In response to cosyntropin stimulation, two participants had peak cortisol levels < 14.6 mcg/dL, consistent with adrenal insufficiency. OXT levels were not significantly different between baseline (343.0 (223.5-451.5)pg/mL) and 5 (347.4 (212.8-575.2)pg/mL, p=0.776),15 (324.1 (225.5-443.3pg/mL), p=0.14), 30 (348.1 (247.4-546.9)pg/mL, p=0.691), and 60 (335.4 (239.6-492.8)pg/mL, p=0.733) minutes after cosyntropin stimulation. Similarly, NP-I concentrations did not differ significantly between baseline (1975.8 (980.5-3084.6) pg/mL) and 5 (1444.0 (963.0-3320.6)pg/mL, p=0.394),15 (1696.9 (878.4-3078.4) pg/mL, p= 0.394), 30 (1702.8 (865.6-3199.7) pg/mL, p=0.733), and 60 (1690.7 (843.4-3174.8) pg/mL, p=0.427) minutes.

Conclusion
The 250 mcg cosyntropin stimulation test did not increase levels of OXT or NP-I, and is not a suitable candidate for OXT-D assessment. A limitation of this study is the inclusion of patients with pituitary hormone deficiencies, which may have attenuated their responses to stimulation; however, none of the participants had a diagnosis of AVP-D. Future studies are needed to identify effective and tolerable OXT stimuli that could serve as the basis for a diagnostic test for OXT-D.

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