Vitamin D, Vitamin D and Calcium Homeostasis
Conditions
Keywords
Vitamin D, Free vitamin D, Free hormone hypothesis
Brief summary
This clinical study aims to gain a better understanding of how different forms of vitamin D are processed in the body in healthy individuals, pregnant women, and patients with various hormonal (endocrine) and kidney (renal) disorders. In the long term, this study may provide new insights that could how vitamin D is tested and interpreted in these groups. Vitamin D has several important roles in the body, such as building strong bones and maintaining calcium balance in the blood. Most vitamin D in the blood circulation is attached/bound to a protein called vitamin D binding protein (VDBP), which makes it unavailable for the body to use. A much smaller portion circulates freely in the blood and this is called free vitamin D. This free form can be directly used by the body. When your doctor tests your vitamin D levels, this usually refers to total vitamin D (the sum of bound and free vitamin D). However, this total value may not give an accurate indication of your actual vitamin D status, since most of it (the bound part) cannot be used by the body. The purpose of this study is to examine whether free vitamin D is a better marker of vitamin D status and if the amount of free vitamin D differs between healthy people, pregnant women, and people with specific endocrine or kidney disorders. Additionally, this study will look into vitamin D metabolism more detailed, and investigate what different forms of vitamin D exist, how the body processes these, and whether these forms may be related to certain endocrine or kidney conditions.
Interventions
Blood draw for the laboratory assessment
Sponsors
KU Leuven
Universitaire Ziekenhuizen KU Leuven
Study design
Observational model
COHORT
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion 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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Direct measurement of free 25-hydroxyvitamin D3 levels | - Baseline (all cohorts) - Baseline (trimester 1, week 1-12) , trimester 2 (week 13-27), trimester 3 (week 28-40) and 4-6 weeks after delivery (Pregnancy) - Baseline, perioperative and 4-8 weeks after parathyroidectomy (Primary Hyperparathyroidism) | 1\) Direct measurement of free 25-hydroxyvitamin D3, reported as concentration levels per cohort; * Reported at baseline * Reported as change versus healthy control group (all cohorts vs healthy control) * Reported as change within-cohort (Pregnancy and Primary Hyperparathyroidism). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Calculation of free 25-hydroxyvitamin D3 levels | - Baseline (all cohorts) - Baseline (trimester 1, week 1-12) , trimester 2 (week 13-27), trimester 3 (week 28-40) and 4-6 weeks after delivery (Pregnancy) - Baseline, perioperative and 4-8 weeks after parathyroidectomy (Primary Hyperparathyroidism) | 1\) Calculation of free 25-hydroxyvitamin D3, reported as concentration levels per cohort; * Reported at baseline * Reported as change versus healthy control group (all cohorts vs healthy control) * Reported as change within-cohort (Pregnancy and Primary Hyperparathyroidism). |
| Correlation of measured and calculated free 25-hydroxyvitamin D3 levels | - Baseline (all cohorts) - Baseline (trimester 1, week 1-12) , trimester 2 (week 13-27), trimester 3 (week 28-40) and 4-6 weeks after delivery (Pregnancy) - Baseline, perioperative and 4-8 weeks after parathyroidectomy (Primary Hyperparathyroidism) | Assessment of correlation between measured (Primary Outcome) and calculated (Secondary Outcome 1) free 25-hydroxyvitamin D3 levels |
| Laboratory assessment of vitamin D metabolite profile | - Baseline (all cohorts) - Baseline (trimester 1, week 1-12) , trimester 2 (week 13-27), trimester 3 (week 28-40) and 4-6 weeks after delivery (Pregnancy) - Baseline, perioperative and 4-8 weeks after parathyroidectomy (Primary Hyperparathyroidism) | Laboratory assessment of different vitamin D metabolites; * 25-hydroxyvitamin D3 * 3-epi-hydroxyvitamin D3 * 1(alpha).25-dihydroxyvitamin D3 * 1(beta).25-dihydroxyvitamin D3 * 3-epi-1.25-dihydroxyvitamin D3 * 24.25-dihydroxyvitamin D3 * 25-hydroxyvitamin D2 * 1.25-dihydroxyvitamin D2 |
Countries
Belgium
Contacts
Primary ContactNick Narinx, MD
Outcome results
None listed