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Animals : an open access journal from MDPI2025; 15(19); 2905; doi: 10.3390/ani15192905

Influence of Extended Photoperiod Using Blue Light Masks on Hypertrichosis, Coat Condition and General Health Parameters in Horses with Pituitary Pars Intermedia Dysfunction.

Abstract: Fifty-two horses aged >15 years, diagnosed with pituitary pars intermedia dysfunction (PPID), and displaying hypertrichosis were recruited via an online survey of PPID horse owners. From mid-December, group T ( = 29) wore Equilume light masks extending photoperiod to 15 h daily, while group C1 ( = 23) remained under natural photoperiod. As 85% (44/52) of recruited study horses received pergolide medication, a second unmedicated PPID research herd (C2; = 17) was recruited and remained under natural photoperiod. Hair coat samples, shedding and body condition scores were collected monthly by owners for 13 months and analysed by the research team. Data related to management, coat condition and PPID clinical signs were collected using bimonthly questionnaires (BMQ). Time ( < 0.001), group ( = 0.025) and time-by-group interaction ( = 0.005) affected hair length. Group differences were attributable to shorter hair lengths in C2, and no differences in hair length occurred between T and C1 ( > 0.05). Time affected shedding scores ( < 0.001) which was advanced by one month in T ( < 0.05). In group T, BMQ responses showed improved coat condition in April ( = 0.035), decreased fat coverage in April and June ( < 0.05), and increased energy/alertness in February ( = 0.022). Improvements in coat condition ( = 0.043), clinical signs of PPID ( = 0.018), and general quality of life ( = 0.035) were reported in T only in a final study questionnaire. Blue light treatment merits further investigation as a complementary treatment for PPID.
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Publication Date: 2025-10-05 PubMed ID: 41096500PubMed Central: PMC12523991DOI: 10.3390/ani15192905Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated the effects of extending daily light exposure using blue light masks on horses with pituitary pars intermedia dysfunction (PPID), focusing on hair growth, coat condition, and overall health.
  • Researchers compared horses receiving blue light therapy to those under natural light conditions, examining hair length, shedding, body condition, and clinical symptoms over 13 months.

Background

  • PPID, also known as equine Cushing’s disease, is a common hormonal disorder in older horses, typically those older than 15 years.
  • The condition often leads to hypertrichosis, which is excessive hair growth, poor coat condition, and other general health issues.
  • Management of PPID usually involves medication such as pergolide, but complementary treatments that might improve symptoms are of interest.
  • Photoperiod, or the length of daily light exposure, has been shown to influence hair growth and shedding cycles in horses.
  • Blue light masks are a novel approach to artificially extend the photoperiod, potentially improving endocrine-related symptoms.

Study Design

  • Participants: 52 horses diagnosed with PPID, exhibiting hypertrichosis, mostly aged over 15 years.
  • Grouping:
    • Group T (n=29): Wore Equilume blue light masks to extend photoperiod to 15 hours daily from mid-December.
    • Group C1 (n=23): Control group under natural photoperiod, most receiving standard pergolide medication.
    • Group C2 (n=17): Unmedicated PPID horses, serving as a second control group under natural photoperiod to account for medication effects.
  • Data Collection:
    • Monthly hair coat samples, shedding assessments, and body condition scoring conducted by horse owners for 13 months.
    • Bimonthly questionnaires to collect data on management, coat condition, and PPID clinical signs.

Key Findings

  • Hair Length:
    • Time (seasonal changes), group membership, and their interaction influenced hair length significantly.
    • Group C2 (unmedicated controls) had shorter hair compared to other groups, indicating natural shedding or better condition without medication.
    • No significant difference in hair length between the blue light treatment group (T) and medicated control group (C1) was found.
  • Shedding Scores:
    • Shedding progressed over time for all groups, but in the blue light group (T), shedding occurred one month earlier, suggesting that extended light exposure may accelerate the shedding cycle.
  • Body Condition and Energy:
    • Owners reported improved coat condition in the blue light group (T) in April.
    • Decreased fat coverage scores, possibly indicating healthier body condition, were noted in April and June in group T.
    • Increased energy and alertness were also reported for the blue light group in February.
  • Overall Health and Clinical Signs:
    • Only horses in the blue light treatment group reported improvements in coat condition, clinical signs of PPID, and general quality of life by study end.
    • These improvements suggest potential therapeutic benefits from extending photoperiod using blue light masks beyond medication alone.

Conclusions and Implications

  • Blue light masks that extend daily light exposure show promise as a complementary treatment for horses with PPID.
  • The intervention may help advance natural hair shedding cycles and improve coat quality and general health status.
  • While blue light treatment did not reduce hair length compared to medicated controls, it positively impacted other clinical signs and subjective health parameters.
  • Further research is recommended to confirm these findings, optimize treatment protocols, and understand mechanisms.
  • This approach could represent a non-pharmacological adjunct therapy, potentially improving quality of life in affected horses.

Cite This Article

APA
Parmantier S, Kyriazopoulou P, McClendon M, Adams A, Murphy BA. (2025). Influence of Extended Photoperiod Using Blue Light Masks on Hypertrichosis, Coat Condition and General Health Parameters in Horses with Pituitary Pars Intermedia Dysfunction. Animals (Basel), 15(19), 2905. https://doi.org/10.3390/ani15192905

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 15
Issue: 19
PII: 2905

Researcher Affiliations

Parmantier, Sinead
  • School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
Kyriazopoulou, Panoraia
  • Equilume Ltd., Ladytown Business Park, Naas, W91 TP22 Co. Kildare, Ireland.
McClendon, Margaret
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA.
Adams, Amanda
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY 40546, USA.
Murphy, Barbara A
  • School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.

Grant Funding

  • n/a / Equilume (Ireland)
  • n/a / University College Dublin
  • n/a / University of Kentucky

Conflict of Interest Statement

B.A.M is a cofounder of Equilume Ltd., a spin-out company deriving from her research as associate professor at University College Dublin and is a member of the company’s board of directors. P.K. was an employee of Equilume Ltd. in the role of research manager at the time of the study.

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