Impact of blue light therapy on plasma adrenocorticotropic hormone (ACTH) and hypertrichosis in horses with pituitary pars intermedia dysfunction.
Abstract: Blue light therapy can be used in horses to alter the natural photoperiod and inhibit winter hair coat growth. Seasonal increases in ACTH occur in the fall season but are exaggerated in horses with pituitary pars intermedia dysfunction (PPID). Additionally, PPID horses frequently present with hypertrichosis. Thus, blue light therapy was proposed as a potential management tool for hypertrichosis and for investigating the impact of photoperiod manipulation on ACTH. Eighteen PPID horses, aged 18 to 31 yr, from a university-owned research herd were selected and assigned to either the control group (n = 10) or the treatment (blue light therapy) group (n = 8) based on age and clinical history, which included the results of multiple endocrine tests. Consistent daylength of approximately 14.5 h was maintained for the treated horses from July 15 through approximately late October via the extension of natural daylength using wearable masks that provided short wavelength blue light (465 nm) to 1 eye. The control group was exposed to only the natural photoperiod during this time. All horses were housed on the same farm and remained on pasture for the duration of the study. On Day 0, thyrotropin-releasing hormone (TRH) stimulation tests were performed to confirm PPID status; there were no differences between the 2 groups in resting plasma ACTH or plasma ACTH at 10 min after TRH administration. To determine an effect of treatment on ACTH, blood was collected via jugular venipuncture for measurement of ACTH at sequential timepoints over a 16-h period in mid-October. Hair weights were also assessed throughout the study. No differences in resting plasma ACTH were observed between the 2 groups across the seasonal analysis (July and October) or during the 16-h testing. The PPID horses receiving blue light therapy had lighter hair weights compared to the PPID control horses. These results suggest that blue light therapy does not alter ACTH concentrations but could potentially be used as an additional management tool for hypertrichosis in PPID horses. Manipulation of the photoperiod using blue light therapy did not affect seasonal changes in ACTH in this study.
Copyright © 2021. Published by Elsevier Inc.
Publication Date: 2021-07-27 PubMed ID: 34656964DOI: 10.1016/j.domaniend.2021.106651Google Scholar: Lookup
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Summary
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The study focuses on how blue light therapy affects the growth of winter hair coat and ACTH hormone levels in horses with pituitary pars intermedia dysfunction (PPID). Main findings indicate that blue light therapy doesn’t affect ACTH concentrations but reduces hair weight growth in PPID horses.
Background
- The research was provoked by the observation that horses with pituitary pars intermedia dysfunction (PPID) have an exaggerated increase in the secretion of the hormone adrenocorticotropic (ACTH) during the fall season.
- PPID horses frequently present with hypertrichosis, a condition of excessive hair growth.
- A hypothesis was proposed that blue light therapy could be used in horses to manipulate the natural photoperiod (day/night cycle), thereby inhibiting winter hair growth and managing hypertrichosis. Furthermore, its effect on ACTH was to be investigated.
Methodology
- Eighteen PPID horses were selected and divided into two groups based on their age and clinical history- a control group (10 horses) and a blue light therapy group (8 horses).
- The control group was exposed to natural photoperiod while the treatment group experienced consistent daylength of approximately 14.5 hours via wearable masks providing short wavelength blue light to one eye. This was done from mid-July to late October.
- To ascertain the PPID status of the horses, thyrotropin-releasing hormone (TRH) stimulation tests were performed. Plasma ACTH levels before and after TRH administration showed no differences between the two groups.
- To evaluate the effect of the therapy on ACTH, blood was collected for ACTH measurement at sequential timepoints over a 16-hour period in mid-October.
- Hair weights were also assessed during this period.
Findings
- The study found no significant difference in resting plasma ACTH levels between the two groups across the seasonal analysis (in July and October) or during the 16-hour testing period.
- However, horses with PPID given blue light therapy had lighter hair weights than the control group.
Conclusion
- Blue light therapy, while not altering ACTH concentrations, was found to potentially be a beneficial management tool for hypertrichosis in PPID horses by assisting in reducing the hair weight.
- The manipulation of photoperiod using blue light therapy had no significant impact on seasonal ACTH changes in this study.
Cite This Article
APA
Miller AB, Murphy BA, Adams AA.
(2021).
Impact of blue light therapy on plasma adrenocorticotropic hormone (ACTH) and hypertrichosis in horses with pituitary pars intermedia dysfunction.
Domest Anim Endocrinol, 78, 106651.
https://doi.org/10.1016/j.domaniend.2021.106651 Publication
Researcher Affiliations
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA. Electronic address: ashton.miller@uky.edu.
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
- M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
MeSH Terms
- Adrenocorticotropic Hormone
- Animals
- Horse Diseases / therapy
- Horses
- Humans
- Hypertrichosis / veterinary
- Phototherapy / veterinary
- Pituitary Diseases / therapy
- Pituitary Diseases / veterinary
- Pituitary Gland, Intermediate / metabolism
Grant Funding
- UL1 TR001998 / NCATS NIH HHS
Citations
This article has been cited 3 times.- Kirkwood NC, Hughes KJ, Stewart AJ. Pituitary Pars Intermedia Dysfunction (PPID) in Horses. Vet Sci 2022 Oct 10;9(10).
- Parmantier S, Kyriazopoulou P, McClendon M, Adams A, Murphy BA. 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) 2025 Oct 5;15(19).
- Farag HI, Murphy BA, Templeman JR, Hanlon C, Joshua J, Koch TG, Niel L, Shoveller AK, Bedecarrats GY, Ellison A, Wilcockson D, Martino TA. One Health: Circadian Medicine Benefits Both Non-human Animals and Humans Alike. J Biol Rhythms 2024 Jun;39(3):237-269.
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