Free vitamin D and steroid metabolism in endocrine and kidney conditions
Free Fraction Vitamin D Measurements to Improve Understanding of Steroid Metabolism in Endocrine Disorders
This project will measure free (unbound) vitamin D and related steroid hormones in adults — including healthy people, pregnant women, and patients with endocrine or kidney disorders — to see how processing differs between groups.
Quick facts
| Study type | Observational |
|---|---|
| Enrollment | 930 (estimated) |
| Ages | 18 Years and up |
| Sex | All |
| Sponsor | Universitaire Ziekenhuizen KU Leuven Academic / other |
| Locations | 1 site (Leuven) |
| Trial ID | NCT07268742 on ClinicalTrials.gov |
What this trial studies
This observational study collects blood samples from adults across several cohorts (healthy controls, people with obesity, chronic kidney disease stage ≥3a, first-trimester pregnancy, primary hyperparathyroidism scheduled for surgery, and complex calcium/phosphate disorders) to measure free and total vitamin D and related steroid markers. Laboratory assays will quantify free vitamin D, total vitamin D, vitamin D binding protein, and selected steroid metabolites to characterize binding and metabolic patterns. The study compares these measures between groups to determine whether total vitamin D testing reflects biologically available free vitamin D in different clinical contexts. Findings are intended to clarify how vitamin D results should be interpreted in pregnancy and in various endocrine and renal disorders.
Who should consider this trial
Good fit: Adults aged 18 or older who can consent and fit one of the study cohorts — healthy controls, people with BMI ≥25 kg/m² (obesity cohort), chronic kidney disease stage ≥3a, women in first-trimester pregnancy, patients with primary hyperparathyroidism scheduled for parathyroidectomy, or those with complex calcium/phosphate disorders — are ideal candidates.
Not a fit: People under 18, those unable to give informed consent, or individuals whose clinical profile does not match any cohort (for example those taking excluded vitamin D or calcium supplementation when applicable) are unlikely to benefit from participation.
Why it matters
Potential benefit: If successful, this could help doctors interpret vitamin D tests more accurately and lead to better diagnosis and treatment for people with pregnancy, endocrine, or kidney conditions.
How similar studies have performed: Previous research on the free vitamin D or 'free hormone' hypothesis has produced promising but mixed results, so the approach is emerging but not yet an established clinical standard.
Eligibility criteria
Show full inclusion / exclusion criteria
1. General inclusion Criteria: \- 18 years or above 2. General exclusion Criteria: * Below 18 years of age * Individuals incapable of providing informed consent 3. Cohort inclusion criteria * Obesity: BMI ≥ 25 kg/m2 * Chronic Kidney Disease: ≥ CKD stage 3a (eGFR \< 60 mL/min/1.73m2) * Pregnancy: in trimester 1 of pregnancy * Primary hyperparathyroidism: diagnosis at UZ Leuven and scheduled for parathyroidectomy at UZ Leuven * Complex calcium and phosphate disorders: diagnosis at UZ Leuven 4. Cohort exclusion criteria * Healthy controls: BMI below 18 kg/m² or above 25 kg/m², pregnancy, chronic kidney disease (independent of staging), primary hyperparathyroidism and vitamin D and/or calcium supplementation * Obesity: chronic kidney disease (independent of staging), pregnancy, primary hyperparathyroidism * Chronic Kidney Disease: BMI below 18 kg/m² or above 30 kg/m², pregnancy, primary hyperparathyroidism * Pregnancy: BMI below 18 kg/m² or above 30 kg/m², chronic kidney disease (independent of staging), primary hyperparathyroidism * Primary hyperparathyroidism: BMI below 18 kg/m² or above 30 kg/m², pregnancy, chronic kidney disease (independent of staging), secondary hyperparathyroidism
Where this trial is running
Leuven
- University Hospitals Leuven — Leuven, Belgium (Recruiting)
Study contacts
- Principal investigator: Leen Antonio, MD, PhD — University Hospitals Leuven, Department of Endocrinology
- Study coordinator: Nick Narinx, MD
- Email: nick.narinx@uzleuven.be
- Phone: +3216348516
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.