Plasma Copeptin in Response to Oral Urea in Healthy Adults and Patients With Polyuria-polydipsia Syndrome

Not Applicable

Completed

Brief Summary: The aim of this study is to investigate whether oral urea stimulates copeptin release and, if so, whether it may provide a novel diagnostic test in the differentiation between AVP-D (Arginine vasopressin deficiency) and PP (primary polydipsia).

Detailed Description: This study consists of two parts, including healthy adults (study part 1 - proof of concept) and adults with an established diagnosis of PP or AVP-D (study part 2 - pilot study).

If the results of study part 1 suggest that oral urea is a potent stimulator of copeptin in healthy adults, study part 2 will be conducted, meaning that adults with an established diagnosis of PP or AVP-D will be included. If study part 1 demonstrates no relevant copeptin increase in response to oral urea, the study will be terminated thereafter and study part 2 will not be conducted.

Recruitment & Eligibility

Inclusion Criteria

Exclusion Criteria

Participation in a trial with investigational drugs within 30 days
Evidence of disordered drinking habits and diuresis defined as polyuria >50ml/kg body weight/24h and polydipsia >3l /24h
Known allergy towards components of the study drink
Pregnancy and breastfeeding
Intention to become pregnant during the study
Evidence of acute illness

Patients

Inclusion Criteria:

Age ≥ 18 years
Documented PP or AVP-D based on accepted diagnostic criteria, i.e., water deprivation test, hypertonic saline infusion test or arginine infusion test. Accordingly, patients must have evidence of disordered drinking habits and diuresis defined as polyuria >50ml/kg body weight/24h and polydipsia >3l /24h or must be on regular daily desmopressin medication

Exclusion Criteria:

Arm && Interventions

Group	Intervention	Description
Study Part 1 urea followed by placebo	Placebo	Participants will undergo a diagnostic test with a single weight-adapted dose of oral urea first. After a a wash-out phase of at least 3 days and not more than 28 days participants will undergo a second diagnostic test with a single weight-adapted dose of placebo.
Study part 2 Urea	Urea	Participants will undergo a diagnostic test with a single weight-adapted dose of oral urea
Study Part 1 placebo followed by urea	Placebo	Participants will undergo a diagnostic test with a single weight-adapted dose of placebo first. After a a wash-out phase of at least 3 days and not more than 28 days participants will undergo a second diagnostic test with a single weight-adapted dose of urea.
Study Part 1 urea followed by placebo	Urea	Participants will undergo a diagnostic test with a single weight-adapted dose of oral urea first. After a a wash-out phase of at least 3 days and not more than 28 days participants will undergo a second diagnostic test with a single weight-adapted dose of placebo.
Study Part 1 placebo followed by urea	Urea	Participants will undergo a diagnostic test with a single weight-adapted dose of placebo first. After a a wash-out phase of at least 3 days and not more than 28 days participants will undergo a second diagnostic test with a single weight-adapted dose of urea.

Primary Outcome Measures

Name	Time	Method
Difference in maximal increase in copeptin levels in plasma (pmol/l)	up to 6 time assessment until 150 minutes after baseline	The difference in maximal increase in copeptin levels in plasma (pmol/l) within 150 minutes after oral intake of urea versus placebo, with the maximal increase being the difference between baseline copeptin values measured at the beginning of the test and maximal values measured between 30 and 150 minutes after ingestion.

Secondary Outcome Measures

Name	Time	Method