Does low vitamin D status cause lower testosterone in women?

Clinical and effectiveness evidence

• Inverse relationship with testosterone: In women, low vitamin D status is not associated with lower testosterone. Instead, observational studies consistently find that lower 25-hydroxyvitamin D [25(OH)D] levels are associated with higher free and total testosterone, while higher vitamin D status is associated with lower free testosterone and higher sex hormone-binding globulin (SHBG).
• Impact of supplementation: Randomized controlled trials (RCTs), particularly in women with polycystic ovary syndrome (PCOS), demonstrate that vitamin D supplementation either reduces or has no effect on testosterone. For example, high-dose vitamin D supplementation (e.g., 4,000 IU/day) significantly reduces total testosterone compared to placebo, while other trials show substantial decreases in free testosterone alongside increases in SHBG.

Mechanistic explanations

• Gonadal expression: The vitamin D receptor (VDR) and its metabolizing enzymes (such as CYP27B1) are highly expressed in female reproductive tissues, including ovarian granulosa, theca, and luteal cells, where they directly regulate follicular development and prevent granulosa-cell senescence.
• Steroidogenic enzyme regulation: Activated VDR binds to vitamin D response elements (VDREs) to transcriptionally regulate essential steroidogenic enzymes. This includes upregulating CYP11A1 (cholesterol side-chain cleavage enzyme) and CYP17A1 in ovarian tissues, which are critical for androgen and estrogen precursor synthesis.
• SHBG modulation: Vitamin D signaling promotes the synthesis of SHBG, a carrier protein produced by the liver. Higher SHBG levels bind free circulating androgens, thereby reducing the bioactive fraction of free testosterone in the circulation.

Limitations and considerations

• Sex-specific differences: While low vitamin D status is associated with lower testosterone levels in men (where VDR activation in Leydig cells supports testicular steroidogenesis), this relationship is inverted in women.
• Confounding by metabolic status: The association between low vitamin D and elevated androgens in women is highly confounded by metabolic health, as insulin resistance concurrently suppresses hepatic SHBG production and impairs vitamin D status.

Bottom line

While vitamin D signaling is mechanistically linked to gonadal function and steroidogenic enzyme expression, low vitamin D status in women is associated with higher (not lower) testosterone levels. Clinical trials show that vitamin D supplementation in women with deficiency reduces free and total testosterone, largely by increasing SHBG levels.