Acute Vitamin D Supplementation on Testosterone in Females

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

RECRUITING

Clinical Phase

NA

Total Enrollment

20 participants

Study Classification

INTERVENTIONAL

Study Start Date

2025-07-01

Study Completion Date

2026-01-30

Brief Summary

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Participation will take place over two visits to the Clinical Exercise Research Center (CERC) at the University of Southern California Health Sciences Campus.

On the first visit, height, weight, and body composition by bioelectrical impedance are recorded. Questionnaires and withdrawal of a sample of blood (1 tablespoon) are also completed. The intervention begins the day following the first visit. The intervention protocol consists of three weeks of consuming either a placebo capsule or a 5000 IU Vitamin D capsule daily and completing a daily survey.

The second visit to CERC immediately follows the 3-weeks intervention. In this visit, the same blood sampling protocol will be completed. The assignment of the intervention will be randomized (i.e., rolling a die), and participants are blinded to group assignment.

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Detailed Description

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High-dose Vitamin D supplementation significantly increases testosterone in men, but research about Vitamin D's effect on testosterone in young, healthy females is limited \[1\]. However, testosterone is a critical hormone for many physiologic functions in females including maintenance of reproductive health, cognitive function, body composition, mental health, bone density, muscle strength, and much more. Thus, this study aims to investigate the effect of Vitamin D supplementation on testosterone and gonadotropin concentrations in premenopausal, healthy females. The study investigators hypothesize that Vitamin D supplementation will result in a significant increase in circulating Vitamin D \[25(OH)D\], testosterone, and sex hormone modulators (i.e., gonadotropins and SHBG) concentrations in pre-menopausal females and that the magnitude of testosterone increase will be inversely related to fat mass and BMI. 20 young, healthy females will be randomized to either a treatment or placebo group for a three-week intervention, where the control group will take 5000 IU of Vitamin D orally, daily and the placebo group will take a placebo capsule orally, daily. Circulating Vitamin D, testosterone, gonadotropin, and SHBG concentrations will be assessed via serum pre- and post-intervention. Two-tailed unpaired t-test will be conducted to assess the relative change in total testosterone and free testosterone levels between the groups. Additionally, correlation analyses will be performed for correlations between body composition metrics and 25(OH)D, testosterone, and sex hormone modulator concentrations.

Conditions

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Female Hormone Profile

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

PARALLEL

Participants will be randomized to either a treatment or control group upon enrollment and blinded to group assignment. The treatment intervention will consist of three weeks of one 5000 IU cholecalciferol capsule (Pure Encapsulations, LLC) daily, with breakfast. The control group will also take a daily, with breakfast, placebo capsule (Zeebo) for the three-week intervention.

Primary Study Purpose

HEALTH_SERVICES_RESEARCH

Blinding Strategy

SINGLE

Participants

Single blinded intervention. Those measuring the blood samples' hormonal will also be blinded to the intervention group but will not have a role in data analysis.

Study Groups

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Vitamin D Group

The treatment intervention will consist of three weeks of one 5000 IU cholecalciferol capsule (Pure Encapsulations, LLC) daily, with breakfast.

Group Type EXPERIMENTAL

Vitamin D (Cholecalciferol )

Intervention Type DIETARY_SUPPLEMENT

5000 IU Vitamin D (as cholecalciferol) capsules (Vitamin D3 125 mcg \[5,000 IU\], Pure Encapsulation, LLC) daily

Placebo Group

The control group will also take a daily, with breakfast, placebo capsule (Zeebo) for the three-week intervention.

Group Type PLACEBO_COMPARATOR

Placebo Group

Intervention Type DIETARY_SUPPLEMENT

One placebo capsule (Zeebo Imagine, Zeebo) daily.

Interventions

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Vitamin D (Cholecalciferol )

5000 IU Vitamin D (as cholecalciferol) capsules (Vitamin D3 125 mcg \[5,000 IU\], Pure Encapsulation, LLC) daily

Intervention Type DIETARY_SUPPLEMENT

Placebo Group

One placebo capsule (Zeebo Imagine, Zeebo) daily.

Intervention Type DIETARY_SUPPLEMENT

Other Intervention Names

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5000 IU Vitamin D daily Placebo (Zeebo) pill daily

Eligibility Criteria

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Inclusion Criteria

* Assigned female at birth
* 18 to 35 years of age
* No chronic diseases affecting the uptake of Vitamin D or causing Vitamin D sensitivity (e.g., sarcoidosis, tuberculosis, Wegener's granulomatosis, other forms of vasculitis, inflammatory bowel diseases, etc.) \[21\]
* Completion and signature of the informed consent document
* Non-pregnant or trying to become pregnant
* No supplementation with Vitamin D within three months of enrollment
* No documented gynecological disease (e.g., PCOS, endometriosis, etc.)
* Weight greater than or equal to 110 lbs

Exclusion Criteria

* Pregnant
* Supplementation with Vitamin D within three months of enrollment
* Taking exogenous hormones
* Documented gynecological disease (e.g., PCOS, endometriosis, etc.)
* Suffering from chronic diseases affecting the uptake of Vitamin D or causing Vitamin D sensitivity (e.g., sarcoidosis, tuberculosis, Wegener's granulomatosis, other forms of vasculitis, inflammatory bowel diseases, etc.) \[21\]
* Weight less than 110 lbs

Minimum Eligible Age

18 Years

Maximum Eligible Age

35 Years

Eligible Sex

FEMALE

Accepts Healthy Volunteers

Yes