To evaluate the effect of vitamin D supplementation on the number and total volume of uterine fibroids in premenopausal women aged 30–45 years with uterine fibroids and vitamin D deficiency.
Design
This study is a randomized, placebo-controlled, parallel-group, double-blind clinical trial. A total of 130 participants will be randomly allocated in a 1:1 ratio to either the vitamin D supplementation group or the placebo group using opaque, sealed envelopes to ensure allocation concealment.
Settings and conduct
This study will be conducted at the gynecology clinics of Imam Hossein Hospital. Eligible women with uterine fibroids and vitamin D deficiency will be randomly assigned to intervention and control groups and followed for 3 months, after which study outcomes will be assessed.
Participants/Inclusion and exclusion criteria
Premenopausal women aged 30–45 years with ultrasonographically confirmed uterine fibroids (total volume 64–512 cm³) and vitamin D deficiency [25(OH)D <20 ng/mL] will be eligible. Exclusion criteria include malabsorption disorders, chronic kidney disease, severe fibroid-related symptoms requiring immediate treatment, cardiovascular disease, diabetes mellitus, malignancy, and osteomalacia or osteoporosis requiring vitamin D therapy.
Intervention groups
Intervention group: Participants with vitamin D insufficiency (12–20 ng/mL) will receive oral vitamin D 1000 IU daily for 3 months. Participants with vitamin D deficiency (<12 ng/mL) will receive vitamin D 50,000 IU weekly for 6–8 weeks followed by 1000 IU daily until completion of the 3-month intervention period.
Control group: Participants will receive a placebo administered according to the same dosing schedule and duration as the intervention group.
Main outcome variables
1. Change in the number and cumulative size of uterine fibroids
2. Serum 25-hydroxyvitamin D [25(OH)D] level
General information
Reason for update
Acronym
IRCT registration information
IRCT registration number:IRCT20251121068065N6
Registration date:2026-06-16, 1405/03/26
Registration timing:prospective
Last update:2026-06-16, 1405/03/26
Update count:0
Registration date
2026-06-16, 1405/03/26
Registrant information
Name
kavoushgaran kavoushgaran
Name of organization / entity
Country
Iran (Islamic Republic of)
Phone
+98 915 718 4680
Email address
atiye.hesary@gmail.com
Recruitment status
recruiting
Funding source
Expected recruitment start date
2026-06-28, 1405/04/07
Expected recruitment end date
2026-09-22, 1405/06/31
Actual recruitment start date
empty
Actual recruitment end date
empty
Trial completion date
empty
Scientific title
The effect of vitamin D on the cumulative size and number of uterine fibroids in women aged 30-45 years with uterine fibroids and hypovitaminosis D.
Public title
The effect of vitamin D on the cumulative size and number of uterine fibroids in women aged 30-45 years with uterine fibroids and hypovitaminosis D.
Purpose
Treatment
Inclusion/Exclusion criteria
Inclusion criteria:
Women aged 30–45 years who are premenopausal.
Presence of uterine fibroids confirmed by abdominal and transvaginal ultrasonography.
Total fibroid volume between 64 and 512 cm³.
Serum 25-hydroxyvitamin D [25(OH)D] level <20 ng/mL (vitamin D deficiency or insufficiency).
Provision of written informed consent.
Exclusion criteria:
Malabsorption disorders.
Chronic kidney disease or renal failure.
Severe fibroid-related symptoms requiring immediate treatment (e.g., heavy bleeding causing anemia, severe pelvic pain, or significant urinary tract compression).
Cardiovascular disease.
Diabetes mellitus.
Any malignancy.
Osteomalacia or osteoporosis requiring therapeutic vitamin D supplementation.
Withdrawal of consent or unwillingness to continue participation.
Age
From 30 years old to 45 years old
Gender
Female
Phase
2
Groups that have been masked
Participant
Outcome assessor
Sample size
Target sample size:
130
Randomization (investigator's opinion)
Randomized
Randomization description
Participants will be randomly allocated to the intervention (vitamin D) or control (placebo) group in a 1:1 ratio using a sealed, opaque envelope randomization method. The randomization sequence will be generated by an independent investigator using Microsoft Excel prior to participant enrollment. Group allocation cards will be prepared in equal numbers and placed in sequentially numbered, opaque, sealed envelopes. After enrollment, each participant will be assigned to a study group by selecting one envelope. This procedure will ensure random allocation and concealment of group assignment throughout the enrollment process.
Blinding (investigator's opinion)
Double blinded
Blinding description
This study will be conducted using a double-blind design. Participants will be unaware of their group allocation (vitamin D or placebo). In addition, the sonographer responsible for ultrasonographic assessments and the experienced midwife involved in participant follow-up and outcome assessment will be blinded to treatment allocation. Therefore, both participants and outcome assessors will remain unaware of group assignment throughout the study.
Placebo
Used
Assignment
Parallel
Other design features
Secondary Ids
empty
Ethics committees
1
Ethics committee
Name of ethics committee
Research Ethics Committee of School of Medicine - Shahid Beheshti University of Medical Sciences
Street address
6th Floor, Building No. 2, Shahid Beheshti University of Medical Sciences Headquarters, Arabi Street, Yemen Street, Shahid Chamran Highway, Tehran, Iran.
City
Tehran
Province
Tehran
Postal code
1985717443
Approval date
2026-05-19, 1405/02/29
Ethics committee reference number
IR.SBMU.MSP.REC.1405.103
Health conditions studied
1
Description of health condition studied
Leiomyoma of uterus (Uterine fibroids)
ICD-10 code
D25
ICD-10 code description
Leiomyoma of uterus
Primary outcomes
1
Description
Number and cumulative size of uterine fibroids.
Timepoint
The number and cumulative volume of uterine fibroids will be assessed at two time points: baseline (prior to initiation of the intervention) and at the end of the 3-month intervention period (post-intervention).
Method of measurement
Fibroid number and cumulative volume will be assessed by transabdominal ultrasonography (TAS) and transvaginal ultrasonography (TVS) performed by a trained sonographer.
2
Description
Serum 25-hydroxyvitamin D [25(OH)D] level
Timepoint
Serum 25-hydroxyvitamin D levels will be measured at two time points: baseline (before initiation of the intervention) and upon completion of the 3-month intervention period.
Method of measurement
Serum 25-hydroxyvitamin D [25(OH)D] levels will be measured using high-performance liquid chromatography (HPLC) with a Pars Azmoon Chromium assay kit.
Secondary outcomes
empty
Intervention groups
1
Description
Control group: Participants will receive a placebo administered according to the same dosing schedule and duration as the intervention group.
Category
Treatment - Drugs
2
Description
Intervention group: Participants with vitamin D insufficiency (12–20 ng/mL) will receive oral vitamin D 1000 IU daily for 3 months. Participants with vitamin D deficiency (<12 ng/mL) will receive vitamin D 50,000 IU weekly for 6–8 weeks followed by 1000 IU daily until completion of the 3-month intervention period.