New Clinical Insights Into Hair Loss Disorders and the Vitamin D Receptor

Recent research has brought new clarity to how hair grows, why it is lost, and the biological systems that control these processes.¹ Hair follicles are small but highly active structures that repeatedly cycle through phases of growth (anagen), regression (catagen), and rest (telogen) throughout life. This cycle depends on constant communication between different cell types within the follicle and on well-coordinated molecular signals. When these signals are disrupted, hair growth can slow or stop, leading to common forms of hair loss.²

Among the regulatory systems now receiving increased attention is the vitamin D receptor (VDR). The VDR is a protein found inside many cells of the skin and hair follicle that helps control which genes are turned on or off. While vitamin D is best known for its role in bone health, research over the past decade has shown that the receptor for vitamin D plays a much broader role in skin and hair biology.

The importance of VDR in hair growth first became clear through animal and human studies. Mice that lack a working VDR develop normal hair initially but lose it after their first hair cycle and cannot regrow it. A similar pattern is seen in people with rare genetic conditions that impair VDR function. Notably, this hair loss occurs even when vitamin D levels are normal, suggesting that the receptor itself, rather than vitamin D alone, is essential for maintaining healthy hair growth.

More recent studies have focused on where the VDR is found within the hair follicle. Researchers have shown that VDR is especially active in the outer layers of the follicle, in the cells that produce the hair shaft, and in the follicle’s stem cell region. These stem cells are responsible for starting new hair growth cycles. VDR activity changes during different stages of the hair cycle, increasing during growth phases and shifting during regression, which supports the idea that it helps guide the timing of hair growth and shedding.

Research has also shown that the VDR does not work in isolation. Instead, it interacts with other key signaling systems that control hair growth, including pathways that regulate cell growth, repair, and immune activity. Through these interactions, the VDR helps balance when hair follicles remain active and when they enter a resting state. This balance is critical for long-term hair maintenance.

Clinical studies have linked changes in VDR activity to several common hair loss conditions. People with alopecia areata and androgenetic alopecia often show reduced VDR levels in scalp tissue compared with individuals without hair loss. Low blood levels of vitamin D are also frequently reported in these patients, although research suggests that correcting vitamin D deficiency alone may not fully restore hair growth if VDR function within the follicle is impaired. In conditions such as telogen effluvium, vitamin D deficiency appears to play a more direct role, and restoring normal levels may support recovery.

These findings have influenced treatment research. Vitamin D supplements are commonly used when deficiency is present, and topical vitamin D–based treatments have shown benefit in some patients, particularly those with alopecia areata. Newer studies are exploring ways to target the VDR more precisely, including improved topical formulations and experimental therapies designed to enhance receptor activity directly within the hair follicle.

Overall, this recent research suggests that the vitamin D receptor is a key regulator of hair growth, helping control hair follicle cycling, stem cell activity, and immune balance in the scalp. While traditional treatments remain important, growing knowledge about VDR function is opening the door to more targeted and personalized approaches for managing hair loss in the future.

References

1. Abreu CM, Marques AP. Recreation of a hair follicle regenerative microenvironment: Successes and pitfalls. Bioeng Transl Med. 2021;7(1):e10235. Published 2021 Jun 23. doi:10.1002/btm2.10235
2. Guan L, Yang F, Li M, et al. The role of vitamin D receptor signaling in hair follicle health and alopecia: Current understanding and therapeutic implications. J Cell Commun Signal. 2025;20(1):e70060. Published 2025 Dec 29. doi:10.1002/ccs3.70060