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Drug testing and analysis2026; doi: 10.1002/dta.70128

Monitoring Estra-4,9-Diene-3,17-Dione Exposure in Equine Hair.

Abstract: This study investigated the incorporation of estra-4,9-diene-3,17-dione (dienedione) and its metabolites into equine hair following exogenous administration and evaluates the potential application of hair analysis for long-term doping surveillance. Mane hair samples were collected from three Thoroughbred castrated horses before and after oral administration of dienedione and from untreated colts for comparison. Dienedione was detected in post-administration hair from all treated horses but was absent in corresponding pre-administration samples. Segmental distribution patterns indicated contributions from both systemic incorporation via hair follicle and external absorption, such as sweat or sebum, with considerable interindividual variability. Three dienedione metabolites (M3a, M7a and M7b), previously reported to exhibit prolonged persistence in plasma and urine, were also detected in hair from the treated horses and showed similar segmental distribution. The absence of detectable dienedione and its monitored metabolites in hair from untreated colts, despite their endogenous presence in urine, suggests that hair analysis may provide more definitive information for the interpretation of dienedione findings following exogenous administration.
© 2026 John Wiley & Sons Ltd.
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Publication Date: 2026-08-07 PubMed ID: 42568238DOI: 10.1002/dta.70128Google Scholar: Lookup
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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 examined how the steroid hormone dienedione and its metabolites are incorporated into horse hair after administration.
  • It assessed whether analyzing horse hair could be useful for long-term monitoring of steroid doping in horses.

Introduction and Objectives

  • The focus was on estra-4,9-diene-3,17-dione, commonly known as dienedione, a steroid with potential doping use in horses.
  • The study aimed to monitor the presence and distribution of dienedione and three of its metabolites in equine hair.
  • A key objective was evaluating equine hair as a sample matrix for long-term doping control, as hair can record drug exposure over extended periods.

Methods

  • Mane hair samples were collected from three Thoroughbred castrated horses both before and after oral administration of dienedione.
  • Hair samples from untreated colts served as control or comparison groups.
  • Segmental analysis of hair was performed to study the distribution of dienedione and metabolites along the hair shaft.
  • The metabolites tracked were M3a, M7a, and M7b, which had been previously identified as showing prolonged persistence in plasma and urine.

Key Findings

  • Dienedione was detected in hair samples after administration in all treated horses but was undetectable before administration.
  • Segmental hair analysis showed that dienedione presence results from both systemic incorporation through hair follicles and external absorption via sweat or sebum.
  • There was considerable variability between individual horses in the level and pattern of incorporation.
  • The three metabolites (M3a, M7a, M7b) were also detected in hair post-treatment, showing similar segmental distribution patterns as the parent compound.
  • None of the metabolites or dienedione were found in the hair of untreated colts, despite their endogenous presence in urine samples.

Implications

  • The absence of dienedione and metabolites in control horse hair suggests that hair analysis can distinguish between endogenous presence and exogenous administration.
  • Hair analysis may offer a complementary or superior approach to urine for detecting long-term or past exposure to steroid doping in horses.
  • The variability in segmental distribution underlines the importance of considering multiple hair segments or sampling strategies for reliable interpretation.
  • External deposition of steroids (via sweat or sebum) should also be accounted for when interpreting hair analysis data.
  • This research supports the potential integration of equine hair testing into anti-doping protocols for horses to enhance long-term surveillance capabilities.

Cite This Article

APA
Ip TKY, So YM, Kwok WH, Yuen SMS, Wong COL, Farrington AF, Bond AJ, Ho ENM. (2026). Monitoring Estra-4,9-Diene-3,17-Dione Exposure in Equine Hair. Drug Test Anal. https://doi.org/10.1002/dta.70128

Publication

Drug testing and analysis
ISSN: 1942-7611
NlmUniqueID: 101483449
Country: England
Language: English

Researcher Affiliations

Ip, Tiffany K Y
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
So, Yat-Ming
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Kwok, Wai Him
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Yuen, Stella M S
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Wong, Celia O L
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Farrington, Adrian F
  • Department of Veterinary Clinical Services, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Bond, Amanda J
  • Department of Equestrian Affairs, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.
Ho, Emmie N M
  • Racing Laboratory, The Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, N. T., Hong Kong, China.

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