Acute Vitamin D Supplementation on Testosterone in Females

Effects of Acute Vitamin D Supplementation on Testosterone in Young, Healthy Females: A Pilot Study

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.

Study Overview

• Status: Active, not recruiting
• Conditions: Female Hormone Profile
• Intervention / Treatment: Dietary supplement: Vitamin D (Cholecalciferol ); Dietary supplement: Placebo Group

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Los Angeles, California, United States, 90033
      • University of Southern California Health Sciences Campus Center for Health Professions

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Health Services Research
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Vitamin D Group; The treatment intervention will consist of three weeks of one 5000 IU cholecalciferol capsule (Pure Encapsulations, LLC) daily, with breakfast.	Dietary supplement: Vitamin D (Cholecalciferol ); 5000 IU Vitamin D (as cholecalciferol) capsules (Vitamin D3 125 mcg [5,000 IU], Pure Encapsulation, LLC) daily; Other Names: 5000 IU Vitamin D daily
Placebo Comparator: Placebo Group; The control group will also take a daily, with breakfast, placebo capsule (Zeebo) for the three-week intervention.	Dietary supplement: Placebo Group; One placebo capsule (Zeebo Imagine, Zeebo) daily.; Other Names: Placebo (Zeebo) pill daily

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Hormonal Effects of Vitamin D in Young, Healthy Women	The primary objective is to evaluate the effect of acute Vitamin D supplementation on systemic Vitamin D, testosterone, and sex hormone modulators in pre-menopausal, healthy females. Circulating testosterone (total testosterone and free testosterone) concentrations (ng/dL) will be assessed via serum pre- and post-Vitamin D intervention.	3 weeks
Hormonal Effects of Vitamin D in Young, Healthy Women	The primary objective is to evaluate the effect of acute Vitamin D supplementation on systemic Vitamin D, testosterone, and sex hormone modulators in pre-menopausal, healthy females. Circulating Vitamin D [25(OH)D] concentrations (ng/dL) will be assessed via serum pre- and post-Vitamin D intervention.	3 weeks
Hormonal Effects of Vitamin D in Young, Healthy Women	The primary objective is to evaluate the effect of acute Vitamin D supplementation on systemic Vitamin D, testosterone, and sex hormone modulators in pre-menopausal, healthy females. Circulating gonadotropins (LH and FSH) concentrations (IU/L) will be assessed via serum pre- and post-Vitamin D intervention.	3 weeks
Hormonal Effects of Vitamin D in Young, Healthy Women	The primary objective is to evaluate the effect of acute Vitamin D supplementation on systemic Vitamin D, testosterone, and sex hormone modulators in pre-menopausal, healthy females. Circulating SHBG concentrations (nmol/L) will be assessed via serum pre- and post-Vitamin D intervention.	3 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Effects of Body Composition on Hormonal Changes Due to Vitamin D Supplementation in Young, Healthy Women	Secondary analyses will evaluate the effect of body composition on change in testosterone concentration due to acute Vitamin D supplementation of pre-menopausal, healthy females. Testosterone (TT and FT) concentrations will be correlated with body composition metrics, i.e. fat and fat-free mass (kg), pre- and post-Vitamin D intervention.	3 weeks
Effects of Body Composition on Hormonal Changes Due to Vitamin D Supplementation in Young, Healthy Women	Secondary analyses will evaluate the effect of body composition on change in testosterone concentration due to acute Vitamin D supplementation of pre-menopausal, healthy females. Testosterone (TT and FT) concentrations will be correlated with body composition metrics, i.e. BMI (kg/m^2) as measured from height (m) and weight (kg), pre- and post-Vitamin D intervention.	3 weeks

Collaborators and Investigators

• Sponsor: University of Southern California
• Investigators: Principal Investigator: Giuliet L Kibler, University of Southern California - Division of Biokinesiology and Physical Therapy

Publications and helpful links

General Publications

• Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 2011 Mar;43(3):223-5. doi: 10.1055/s-0030-1269854. Epub 2010 Dec 10.

Study record dates

Study Major Dates

• Study Start (Actual): July 1, 2025
• Primary Completion (Actual): March 5, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: September 17, 2024
• First Submitted That Met QC Criteria: September 20, 2024
• First Posted (Actual): September 24, 2024

Study Record Updates

• Last Update Posted (Actual): March 25, 2026
• Last Update Submitted That Met QC Criteria: March 24, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Lipids; Polycyclic Compounds; Steroids; Fused-Ring Compounds; Cholestenes; Cholestanes; Sterols; Vitamin D; Secosteroids; Membrane Lipids; Cholecalciferol
• Other Study ID Numbers: HS-24-00403

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No