Topic:Androgens
Androgens are a group of steroid hormones that play a crucial role in the development and maintenance of male characteristics in horses, although they are present in both males and females. These hormones, including testosterone and androstenedione, are primarily produced in the testes, ovaries, and adrenal glands. Androgens are involved in regulating reproductive functions, influencing muscle development, and modulating behavior. In equine research, androgens are studied for their impact on performance, breeding, and overall health. Abnormal androgen levels can lead to conditions such as stallion-like behavior in mares or fertility issues. This page compiles peer-reviewed research studies and scholarly articles that explore the physiological roles, regulatory mechanisms, and clinical implications of androgens in equine health and management.
Androgen Insensitivity Syndrome in a Family of Warmblood Horses Caused by a 25-bp Deletion of the DNA-Binding Domain of the Androgen Receptor Gene. Testicular feminization, an earlier term coined for describing a syndrome resulting from failure of masculinization of target organs by androgen secretions during embryo development, has been well documented not only in humans but also in the domestic horse. The pathology, actually referred to as androgen insensitivity syndrome (AIS), has been proposed to follow an X-linked recessive pattern of inheritance in some horse breeds already investigated. Affected individuals are characterized by a female phenotype but with a stallion genotype of 64,XY SRY+ constitution. We identified a Warmblood hor...
A comparison of fecal steroid metabolite concentrations between harem and bachelor stallions in a free-Ranging population of przewalski’s horses (Equus ferus przewalskii). The aim of this study was to determine whether concentrations of reproductive steroid hormone metabolites significantly differed between harem stallions and bachelor stallions in the free ranging group of Przewalski's horses (Equus ferus przewalskii) at the Hortobágy National Park in Hungary. Throughout the study, fecal samples were collected from 21 harem stallions and 15 bachelor stallions and analyzed for immunoreactive estrogen and androgen metabolites. Harem stallions demonstrated significantly higher concentrations of estrogen (P < 0.001) and epi-androsterone (P < 0.001), ...
Mouldy feed: A possible explanation for the excretion of anabolic-androgenic steroids in horses. To ensure fair competition and to protect the horse's welfare, horses have to compete on their own merits, without any unfair advantage that might follow the use of drugs. Therefore, regulatory authorities list all substances that are not allowed in competition, including most anabolic-androgenic steroids. As zero-tolerance is retained, the question arose whether the consumption of mouldy feed could lead to the excretion of steroids, due to the biotransformation of plant phytosterols to steroids. A rapid ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analyt...
New flow cytometry approaches in equine andrology. Flow cytometry is currently recognized as a robust tool for the evaluation of sperm quality and function. However, within equine reproduction, this technique has not reached the sophistication of other areas of biology and medicine. In recent years, more sophisticated flow cytometers have been introduced in andrology laboratories, and the number of tests that can be potentially used in the evaluation of sperm physiology has increased accordingly. In this review, recent advances in the evaluation of stallion spermatozoa will be discussed. These new techniques in flow cytometry are able to simul...
Review of the reproductive endocrinology of the pregnant and parturient mare. Analytical advancements, especially methods using gas or liquid chromatography tandem mass spectrometry, have allowed more specific and reliable measurement of multiple steroid hormones in the plasma of mares throughout gestation and the periparturient period. Data such as these will form the central focus of this review. The comprehensive analyses possible with liquid chromatography tandem mass spectrometry illuminate the key physiological and developmental transitions that make equine gestation unique. Weeks 6 to 20 encompass endometrial cup formation and equine chorionic gonadotropic secret...
Missense Mutation in the Ligand-Binding Domain of the Horse Androgen Receptor Gene in a Thoroughbred Family with Inherited 64,XY (SRY+) Disorder of Sex Development. Disorders of sex development (DSD) have long been documented in domestic animal species including horses. However, there is only a single report of an androgen receptor (AR) mutation causative of such a DSD syndrome in a horse pedigree. Here, we present a new familial AR mutation in horses. A missense mutation (c.2042G>C) at AR exon 4 explains the segregation of the DSD in a Thoroughbred horse pedigree. The mutation, expected to affect the ligand-binding domain of the AR protein, led to complete androgen insensitivity of 64,XY SRY+, testicular DSD individuals. Additionally, the design of a ...
Investigation of the selective androgen receptor modulators S1, S4 and S22 and their metabolites in equine plasma using high-resolution mass spectrometry. Selective androgen receptor modulators (SARMs) are prohibited in sports due to their performance enhancing ability. It is important to investigate the metabolism to determine appropriate targets for doping control. This is the first study where the equine metabolites of SARMs S1, S4 (Andarine) and S22 (Ostarine) have been studied in plasma. Methods: Each SARM was administered to three horses as an intravenous bolus dose and plasma samples were collected. The samples were pretreated with protein precipitation using cold acetonitrile before separation by liquid chromatography. The mass spectrome...
Changes in maternal androgens and oestrogens in mares with experimentally-induced ascending placentitis. While advanced stages of ascending placentitis can be diagnosed by transrectal ultrasonography and clinical signs, early stages can be missed. Thus, additional tools could enhance assessment of placental health. Objective: To characterise peripheral dehydroepiandrosterone sulphate (DHEA-S) and testosterone concentrations in mares carrying normal pregnancies (Study 1) and compare plasma concentrations of DHEA-S, testosterone, oestradiol 17-β (oestradiol) and oestrone sulphate (OES) in mares with or without placentitis (Study 2). Methods: Longitudinal cohort study of healthy mares (Study 1) and...
Evaluation of chemical castration with calcium chloride versus surgical castration in donkeys: testosterone as an endpoint marker. For the last few years, researchers have been interested in developing a method for chemical sterilization which may be a better alternative to surgical castration. An ideal chemical sterilant would be one that effectively arrests spermatogenesis and androgenesis as well as libido with absence of toxic or other side effects. Calcium chloride in various solutions and concentrations has been tested in many animal species, but few studies have been evaluated it in equines as a chemical sterilant. So, the objective of this study was to evaluate the clinical efficacy of chemical castration with 20%...
Endocrine, morphometric, and ultrasonographic characterization of neck adiposity in Andalusian horses. Equine metabolic syndrome (EMS) can be diagnosed by hormonal measurements; however, it would be important to find simpler measurements that allow easy identification of affected or at risk individuals. In horses, the dorsal neck region is one of the most frequent anatomical sites for fat deposition and neck obesity has been linked to EMS. The aim of this study was to evaluate the association of hormonal markers of obesity (leptin) and insulin resistance (insulin) with morphometric and ultrasonographic neck measurements in Andalusian horses. Plasma leptin and insulin concentrations were measure...
In vivo and in vitro metabolism of the designer anabolic steroid furazadrol in thoroughbred racehorses. Furazadrol ([1',2']isoxazolo[4',5':2,3]-5α-androstan-17β-ol) is a designer anabolic androgenic steroid that is readily available via the internet. It contains an isoxazole fused to the steroid A-ring which offers metabolic stability and noteworthy anabolic activity raising concerns over the potential for abuse of this compound in equine sports. The metabolism of furazadrol was studied by in vivo and in vitro methods for the first time. Urinary furazadrol 17-sulfate and furazadrol 17-glucuronide metabolites were detected in vivo after a controlled administration and compared with syntheticall...
The dynamic steroid landscape of equine pregnancy mapped by mass spectrometry. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) allowed comprehensive analysis of various steroids detectable in plasma throughout equine gestation. Mares (n=9) were bled serially until they foaled. Certain steroids dominated the profile at different stages of gestation, clearly defining key physiological and developmental transitions. The period (weeks 6-20) coincident with equine chorionic gonadotropic (eCG) stimulation of primary corpora lutea and subsequent formation of secondary luteal structures was defined by increased progesterone, 17OH-progesterone and androstenedione, all Î...
Targeted Metabolomics Approach To Detect the Misuse of Steroidal Aromatase Inhibitors in Equine Sports by Biomarker Profiling. The use of anabolic androgenic steroids (AAS) is prohibited in both human and equine sports. The conventional approach in doping control testing for AAS (as well as other prohibited substances) is accomplished by the direct detection of target AAS or their characteristic metabolites in biological samples using hyphenated techniques such as gas chromatography or liquid chromatography coupled with mass spectrometry. Such an approach, however, falls short when dealing with unknown designer steroids where reference materials and their pharmacokinetics are not available. In addition, AASs with fast...
Elevated testosterone levels in a racing horse due to an XY testicular disorder of sexual development. A female thoroughbred successful in horse racing was positively tested for high testosterone values. This horse neither showed stallion-like-behaviour nor signs of ambiguous external genitalia. The karyotype of this horse was 2n = 64,XY and the sex-determining region of Y (SRY) PCR was positive. Hair samples tested for naturally testosterone revealed values normal for stallions, and tests for eight synthetic testosterone esters remained negative. The phenotype, ultrasonographic examination, hormone status, cytogenetic evaluation and molecular diagnostics lead to the diagnosis of an XY testicul...
5Alpha-Reduced Steroids Are Major Metabolites in the Early Equine Embryo Proper and Its Membranes. Steroid production and metabolism by early conceptuses are very important for the establishment and maintenance of pregnancy in horses. Our earlier work suggested the possible formation of 5alpha-reduced steroids in equine conceptuses. We have now demonstrated the formation of 5alpha-reduced metabolites of androstenedione, testosterone, and progesterone by the embryo and its membranes. A total of 44 conceptuses were collected from 26 mares between 20 and 31 days of pregnancy. Tissues from the embryo proper and from the separated components of the conceptus (bilaminar and trilaminar trophoblast...
Androgen receptor gene polymorphism in zebra species. Androgen receptor genes (AR) have been found to have associations with reproductive development, behavioral traits, and disorders in humans. However, the influence of similar genetic effects on the behavior of other animals is scarce. We examined the loci AR glutamine repeat (ARQ) in 44 Grevy's zebras, 23 plains zebras, and three mountain zebras, and compared them with those of domesticated horses. We observed polymorphism among zebra species and between zebra and horse. As androgens such as testosterone influence aggressiveness, AR polymorphism among equid species may be associated with diffe...
In vitro simulation of the equine hindgut as a tool to study the influence of phytosterol consumption on the excretion of anabolic-androgenic steroids in horses. Traditionally, steroids other than testosterone are considered to be synthetic, anabolic steroids. Nevertheless, in stallions, it has been shown that β-Bol can originate from naturally present testosterone. Other precursors, including phytosterols from feed, have been put forward to explain the prevalence of low levels of steroids (including β-Bol and ADD) in urine of mares and geldings. However, the possible biotransformation and identification of the precursors has thus far not been investigated in horses. To study the possible endogenous digestive transformation, in vitro simulations of t...
Metabolic study of androsta-1,4,6-triene-3,17-dione in horses using liquid chromatography/high resolution mass spectrometry. Androsta-1,4,6-triene-3,17-dione (ATD) is an irreversible steroidal aromatase inhibitor and is marketed as a supplement. It has been reported to effectively reduce estrogen biosynthesis and significantly increase the levels of endogenous steroids such as dihydrotestosterone and testosterone in human. ATD abuses have been reported in human sports. Its metabolism in human has been studied, and the in vitro metabolic study of ATD in horses has been reported, however, little is known about its biotransformation and elimination in horses. This paper describes the in vitro and in vivo metabolism stu...
A validated UHPLC-MS/MS method to quantify low levels of anabolic-androgenic steroids naturally present in urine of untreated horses. Doping control is a main priority for regulatory bodies of both the horse racing industry and the equestrian sports. Urine and blood samples are screened for the presence of hundreds of forbidden substances including anabolic-androgenic steroids (AASs). Based on the suspected endogenous origin of some AASs, with β-boldenone as the most illicit candidate, this study aimed to improve the knowledge of the naturally present AAS in horse urine. To this extent, a novel ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated according to...
Characterization of equine urinary metabolites of selective androgen receptor modulators (SARMs) S1, S4 and S22 for doping control purposes. Selective androgen receptor modulators, SARMs, constitute a class of compounds with anabolic properties but with few androgenic side-effects. This makes them possible substances of abuse and the World Anti-Doping Agency (WADA) has banned the entire class of substances. There have been several cases of illicit use of aryl propionamide SARMs in human sports and in 2013, 13 cases were reported. These substances have been found to be extensively metabolized in humans, making detection of metabolites necessary for doping control. SARMs are also of great interest to equine doping control, but the in...
Inhibition of in vitro metabolism of testosterone in human, dog and horse liver microsomes to investigate species differences. Testosterone hydroxylation was investigated in human, canine and equine liver microsomes and in human and canine single CYPs. The contribution of the CYP families 1, 2 and 3 was studied using chemical inhibitors. Testosterone metabolites were analyzed by HPLC. The metabolites androstenedione, 6β- and 11β-hydroxytestosterone were found in microsomes of all species, but the pattern of metabolites varied within species. Androstenedione was more prominent in the animal species, and an increase over time was seen in equines. Testosterone hydroxylation was predominantly catalyzed by the CYP3A subf...
Disposition and metabolic profile of the weak androgen Dehydroepiandrosterone (DHEA) following administration as part of a nutritional supplement to exercised horses. In order to ensure the welfare of performance horses and riders as well as the integrity of the sport, the use of both therapeutic and illegal agents in horse racing is tightly regulated. While Dehydroepiandrosterone (DHEA) is not specifically banned from administration to racehorses in the United States and no screening limit or threshold concentration exists, the metabolic conversion of DHEA to testosterone make its presence in nutritional supplements a regulatory concern. The recommended regulatory threshold for total testosterone in urine is 55 and 20 ng/mL for mares and geldings, respec...
Dexamethasone acutely down-regulates genes involved in steroidogenesis in stallion testes. In rodents, livestock and primate species, a single dose of the synthetic glucocorticoid dexamethasone acutely lowers testosterone biosynthesis. To determine the mechanism of decreased testosterone biosynthesis, stallions were treated with 0.1mg/kg dexamethasone 12h prior to castration. Dexamethasone decreased serum concentrations of testosterone by 60% compared to saline-treated control stallions. Transcriptome analyses (microarrays, northern blots and quantitative PCR) of testes discovered that dexamethasone treatment decreased concentrations of glucocorticoid receptor alpha (NR3C1), alpha a...
Control of the misuse of testosterone in castrated horses based on an international threshold in plasma. Testosterone is an endogenous steroid produced primarily in the testes. Trace levels of testosterone are found in urine samples from geldings, as testosterone is also secreted by the adrenal. An international threshold of free and conjugated testosterone in urine (20 ng/mL) was adopted by the International Federation of Horseracing Authorities (IFHA) in 1996 for controlling testosterone misuse in geldings. In view of the recent popularity of using blood in doping control testing, it is necessary to establish a threshold for testosterone in gelding plasma. A liquid chromatography-mass spectro...
Indenopyride derivative RTI-4587-073(l): a candidate for male contraception in stallions. The objective of this study was to determine whether an indenopyridine derivative RTI-4587-073(l) was a good candidate for male contraception in horses. We hypothesized that a single administration of RTI-4587-073(l) causes significant suppression of testicular function in stallions without affecting sexual behavior. Three Miniature horse stallions received a single dose of 12.5 mg/kg RTI-4587-073(l) orally (group "treated"), whereas three other Miniature horse stallions received placebo only (group "control"). Semen was collected and evaluated from all stallions twice a week for three baselin...
Monitoring the endogenous steroid profile disruption in urine and blood upon nandrolone administration: An efficient and innovative strategy to screen for nandrolone abuse in entire male horses. Nandrolone (17β-hydroxy-4-estren-3-one) is amongst the most misused endogenous steroid hormones in entire male horses. The detection of such a substance is challenging with regard to its endogenous presence. The current international threshold level for nandrolone misuse is based on the urinary concentration ratio of 5α-estrane-3β,17α-diol (EAD) to 5(10)-estrene-3β,17α-diol (EED). This ratio, however, can be influenced by a number of factors due to existing intra- and inter-variability standing, respectively, for the variation occurring in endogenous steroids concentration levels in a si...
Investigations into the feasibility of routine ultra high performance liquid chromatography-tandem mass spectrometry analysis of equine hair samples for detecting the misuse of anabolic steroids, anabolic steroid esters and related compounds. The detection of the abuse of anabolic steroids in equine sport is complicated by the endogenous nature of some of the abused steroids, such as testosterone and nandrolone. These steroids are commonly administered as intramuscular injections of esterified forms of the steroid, which prolongs their effects and improves bioavailability over oral dosing. The successful detection of an intact anabolic steroid ester therefore provides unequivocal proof of an illegal administration, as esterified forms are not found endogenously. Detection of intact anabolic steroid esters is possible in plasma samp...
Abnormal plasma neuroactive progestagen derivatives in ill, neonatal foals presented to the neonatal intensive care unit. Increased levels of pregnanes have been reported in foals with neonatal maladjustment syndrome (NMS). These steroids may cross the blood-brain barrier and have depressive effects in the central nervous system leading to behavioural abnormalities and altered states of consciousness in affected foals. Objective: The aim of this study was to determine the pregnane profile of foals with NMS and compare it with that of healthy controls and sick, non-NMS foals. Methods: Prospective-clinical study. Methods: Thirty-two foals with a clinical diagnosis of NMS, 12 foals with other neonatal disorders and ...
Metabolic studies of formestane in horses. Formestane (4-hydroxyandrost-4-ene-3,17-dione) is an irreversible steroidal aromatase inhibitor with reported abuse in human sports. In 2011, our laboratory identified the presence of formestane in a horse urine sample from an overseas jurisdiction. This was the first reported case of formestane in a racehorse. The metabolism of formestane in humans has been reported previously; however, little is known about its metabolic fate in horses. This paper describes the in vitro and in vivo metabolic studies of formestane in horses, with the objective of identifying the target metabolite with the lon...