Arginine or Hypertonic Saline-Stimulated Copeptin to Diagnose AVP Deficiency.

BACKGROUND: Distinguishing between arginine vasopressin (AVP) deficiency and primary polydipsia is challenging. Hypertonic saline-stimulated copeptin has been used to diagnose AVP deficiency with high accuracy but requires close sodium monitoring. Arginine-stimulated copeptin has shown similar diagnostic accuracy but with a simpler test protocol. However, data are lacking from a head-to-head comparison between arginine-stimulated copeptin and hypertonic saline-stimulated copeptin in the diagnosis of AVP deficiency. METHODS: In this international, noninferiority trial, we assigned adult patients with polydipsia and hypotonic polyuria or a known diagnosis of AVP deficiency to undergo diagnostic evaluation with hypertonic-saline stimulation on one day and with arginine stimulation on another day. Two endocrinologists independently made the final diagnosis of AVP deficiency or primary polydipsia with use of clinical information, treatment response, and the hypertonic-saline test results. The primary outcome was the overall diagnostic accuracy according to prespecified copeptin cutoff values of 3.8 pmol per liter after 60 minutes for arginine and 4.9 pmol per liter once the sodium level was more than 149 mmol per liter for hypertonic saline. RESULTS: Of the 158 patients who underwent the two tests, 69 (44%) received the diagnosis of AVP deficiency and 89 (56%) received the diagnosis of primary polydipsia. The diagnostic accuracy was 74.4% (95% confidence interval [CI], 67.0 to 80.6) for arginine-stimulated copeptin and 95.6% (95% CI, 91.1 to 97.8) for hypertonic saline-stimulated copeptin (estimated difference, -21.2 percentage points; 95% CI, -28.7 to -14.3). Adverse events were generally mild with the two tests. A total of 72% of the patients preferred testing with arginine as compared with hypertonic saline. Arginine-stimulated copeptin at a value of 3.0 pmol per liter or less led to a diagnosis of AVP deficiency with a specificity of 90.9% (95% CI, 81.7 to 95.7), whereas levels of more than 5.2 pmol per liter led to a diagnosis of primary polydipsia with a specificity of 91.4% (95% CI, 83.7 to 95.6). CONCLUSIONS: Among adult patients with polyuria polydipsia syndrome, AVP deficiency was more accurately diagnosed with hypertonic saline-stimulated copeptin than with arginine-stimulated copeptin. (Funded by the Swiss National Science Foundation; CARGOx ClinicalTrials.gov number, NCT03572166.).

Oxytocin in response to MDMA provocation test in patients with arginine vasopressin deficiency (central diabetes insipidus): a single-centre, case-control study with nested, randomised, double-blind, placebo-controlled crossover trial.

BACKGROUND: Disruptions of the hypothalamic-pituitary axis can cause an arginine vasopressin deficiency, also known as central diabetes insipidus. Patients with this condition are at high risk of additional oxytocin deficiency owing to the close anatomical proximity of oxytocin-producing neurons; however, no conclusive evidence for such a deficiency has been reported. We aimed to use 3,4-methylenedioxymethamphetamine (MDMA, also known as ecstasy), a strong activator of the central oxytocinergic system, as a biochemical and psychoactive provocation test to investigate oxytocin deficiency in patients with arginine vasopressin deficiency (central diabetes insipidus). METHODS: This single-centre, case-control study with nested, randomised, double-blind, placebo-controlled crossover trial included patients with arginine vasopressin deficiency (central diabetes insipidus) and healthy controls (matched 1:1 by age, sex, and BMI) and was conducted at the University Hospital Basel, Basel, Switzerland. We used block randomisation to assign participants to receive either a single oral dose of MDMA (100 mg) or placebo in the first experimental session; patients received the opposite treatment at the next session, with a wash-out period of at least 2 weeks between the two sessions. Participants and investigators assessing the outcomes were masked to assignment. Oxytocin concentrations were measured at 0, 90, 120, 150, 180, and 300 min after MDMA or placebo. The primary outcome was the area under the plasma oxytocin concentration curve (AUC) after drug intake. The AUC was compared between groups and conditions using a linear mixed-effects model. Subjective drug effects were assessed throughout the study using ten-point visual analogue scales. Acute adverse effects were assessed before and 360 min after drug intake using a 66-item list of complaints. This trial is registered with ClinicalTrials.gov, NCT04648137. FINDINGS: Between Feb 1, 2021, and May 1, 2022, we recruited 15 patients with arginine vasopressin deficiency (central diabetes insipidus) and 15 healthy controls. All participants completed the study and were included in the analyses. In healthy controls, median plasma oxytocin concentration was 77 pg/mL (IQR 59-94) at baseline and increased by 659 pg/mL (355-914) in response to MDMA, resulting in an AUC of 102 095 pg/mL (41 782-129 565); in patients, baseline oxytocin concentration was 60 pg/mL (51-74) and only slightly increased by 66 pg/mL (16-94) in response to MDMA, resulting in an AUC of 6446 pg/mL (1291-11 577). The effect of MDMA on oxytocin was significantly different between groups: the AUC for oxytocin was 82% (95% CI 70-186) higher in healthy controls than in patients (difference 85 678 pg/mL [95% CI 63 356-108 000], p<0·0001). The increase in oxytocin in healthy controls was associated with typical strong subjective prosocial, empathic, and anxiolytic effects, whereas only minimal subjective effects were observed in patients, in agreement with the lack of increase in oxytocin concentrations. The most frequently reported adverse effects were fatigue (eight [53%] healthy controls and eight [53%] patients), lack of appetite (ten [67%] healthy controls and eight [53%] patients), lack of concentration (eight [53%] healthy controls and seven [47%] patients), and dry mouth (eight [53%] healthy controls and eight [53%] patients). In addition, two (13%) healthy controls and four (27%) patients developed transient mild hypokalaemia. INTERPRETATION: These findings are highly suggestive of clinically meaningful oxytocin deficiency in patients with arginine vasopressin deficiency (central diabetes insipidus), laying the groundwork for a new hypothalamic-pituitary disease entity. FUNDING: Swiss National Science Foundation, Swiss Academy of Medical Sciences, and the G&J Bangerter-Rhyner Foundation.