Free Vitamin D and Steroid Metabolism in Endocrine Disorders (FREEDOM)

Universitaire Ziekenhuizen KU Leuven

Status: Enrolling

Conditions: Vitamin D and Calcium Homeostasis; Vitamin D

Treatments: Other: Blood draw for the laboratory assessment

Study type: Observational

Funder types: Other

Identifiers

NCT07268742

S67385

Details and patient eligibility

About

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.

Enrollment: 930 estimated patients

Sex: All

Ages: 18+ years old

Volunteers: Accepts Healthy Volunteers

Inclusion and 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

Trial design

930 participants in 6 patient groups

Healthy Controls

Description:

1. 264 individuals, consisting of; * 132 men * 132 women 2. Intervention - Single venous blood draw

Treatment:

Other: Blood draw for the laboratory assessment

Obesity

Description:

1. 132 individuals with obesity, subgrouped according to obesity class * 33 individuals with overweight, BMI 25.0-29.9 kg/m² * 33 individuals in obesity class I BMI 30.0-34.9 kg/m² * 33 individuals in obesity class II BMI 35.0-39.9 kg/m² * 33 individuals in obesity class III BMI equal to or greater than 40.0 kg/m² 2. Intervention - Single venous blood draw

Treatment:

Other: Blood draw for the laboratory assessment

Chronic Kidney Disease

Description:

1. 132 individuals with chronic kidney disease (CKD), subgrouped according to CKD staging; * 33 individuals in class 3a, eGFR 45 - 59 mL/min/1.73m² * 33 individuals in class 3b, eGFR 30 - 44 mL/min/1.73m² * 33 individuals in class 4, eGFR 15 - 29 mL/min/1.73m² * 33 individuals in class 5, eGFR \<15 mL/min/1.73m² 2. Intervention - Single venous blood draw

Treatment:

Other: Blood draw for the laboratory assessment

Pregnancy

Description:

1. 132 pregnant women; \- recruited during the first trimester of pregnancy 2. Intervention * Venous blood draw * At 4 timepoints: trimester 1 (week 1-12) , trimester 2 (week 13-27), trimester 3 (week 28-40) and 4-6 weeks after delivery

Treatment:

Other: Blood draw for the laboratory assessment

Primary Hyperparathyroidism

Description:

1. 220 individuals with primary hyperparathyroidism * New diagnosis or previously untreated by surgery * With an indication for surgery (parathyroidectomy, PTX)) 2. Intervention * Venous blood draw * At 3 timepoints: at diagnosis (pre-PTX), day 1 after PTX and post-PTX (during a standard-of-care follow-up visit)

Treatment:

Other: Blood draw for the laboratory assessment

Complex calcium/phosphate disorders

Description:

1. Individuals with complex calcium and phosphate homeostasis disorders 2. Intervention - Single venous blood draw

Treatment:

Other: Blood draw for the laboratory assessment