Growth hormone (GH) in horses is a peptide hormone produced by the pituitary gland, playing a significant role in growth, metabolism, and overall development. It influences various physiological processes, including protein synthesis, cell growth, and the regulation of bone and muscle development. In equine physiology, GH impacts energy metabolism and can affect performance and recovery. Researchers study the secretion patterns, regulatory mechanisms, and effects of GH to understand its role in equine health and performance. This page compiles peer-reviewed research studies and scholarly articles that explore the biology, regulation, and implications of growth hormone in horses, providing insights into its effects on growth, metabolism, and athletic performance.
Fukushima JG, Cascone O, Santomé JA, Biscoglio de Jimenez Bonino MJ.Reactivity of histidine residues in equine growth hormone to ethoxyformic anhydride was studied. The existence of two kinetically different sets was demonstrated: one of them including only the slow reacting histidine 169 (k = 0.164 min-1) and the other containing fast reacting histidines 19 and 21 (k = 0.892 min-1). A correlation between the decrease in the capacity to compete with 125I-labeled hormone for rat liver binding sites and the degree of ethoxyformylation of the fast group was found. Circular dichroism studies indicated no significant conformational changes in the protein with all t...
Schryver HF, Meakim DW, Lowe JE, Williams J, Soderholm LV, Hintz HF.The effect of level of protein intake on growth and calcium metabolism was studied in 24 foals. Starting at four months old, the foals were fed one of three diets containing all nutrients, with the exception of protein, at levels recommended by the United States National Research Council Subcommittee on Horse Nutrition for a 12 month period. The protein levels in the three diets were 9 per cent (low protein) 14 per cent (NRC recommended level) and 20 per cent (high protein). The foals fed the low protein diet were changed to the high protein diet after 140 days when they were nine months old. ...
Stewart F, Leigh SE, Thomson JA.Complementary (c)DNA libraries have been made from horse pituitary gland and endometrial cup tissues with the aim of isolating the genes for the horse gonadotrophins (FSH, LH and CG) and growth hormone (GH). Southern (DNA) and Northern (RNA) blotting techniques were used to demonstrate that several heterologous (human and ovine) cDNA probes would be adequate for isolating the horse genes. A human cDNA probe was then used to isolate the horse gonadotrophin alpha-subunit cDNA from the pituitary and endometrial cup libraries. The nucleotide sequences from both tissue sources were identical, there...
Sandusky GE, Wightman KA.Specific cell populations in the pituitary glands of the rat, cat, pig, and human being were positive for thyroid-stimulating hormone (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). When reacted with prediluted rabbit anti-human TSH, LH, and FSH, antisera were not positive for the demonstration of these hormones in the horse, cow, or dog. Immunocytochemical staining was obtained in the horse, cow, and dog by the use of a primary antiserum against a specific beta-subunit of bovine TSH. The immunocytochemical staining of TSH, LH, FSH, adrenocorticotropic hormone, growth ...
Glade MJ, Gupta S, Reimers TJ.Growth-related skeletal diseases in young horses have been associated with high planes of nutrition, although the mechanisms underlying such an association have not been determined. It is likely that nutrition-induced effects on growth rate or growth quality involve the endocrine system. Hormonal and metabolic responses to the ingestion of meals containing either 80% (diet A) or 160% (diet B) of National Research Council energy and protein recommendations were examined in eight Thoroughbred weanling horses after 3 wk of dietary adaptation. After 24 h fasts, prefeeding serum concentrations of t...
Wilson CA, ter Haar MB, Bonney RC, Buckingham J, Dixson AF, Yeo T.We have shown previously that pregnant mare serum gonadotrophin (PMSG) induces ovulation only in rats weighing over 60 g on the day of injection. The under-60 g rats do not ovulate although they secrete a preovulatory surge of a pleiomorphic form of LH. Presumably this pleiomorph is inactive. Comparisons were made of plasma hormone concentrations in rats treated with PMSG that weighed over and under 60 g. The measurements were made on samples taken between 13.00 and 22.00 h on the day of the expected preovulatory LH surge. Prolactin and corticosterone levels were lower in the lighter group com...
Poskus E, Peña C, Pérez AR, Vita N, Heinrich JJ, Paladini AC.The immunological behavior of sera from hypopituitary patients treated with human GH (hGH) has been studied by homologous and heterologous RIAs using 125I-labeled hormones. Along with antibodies against hGH, antibodies exhibiting antibovine and antiequine GH (anti-bGH and anti-eGH, respectively) activities were also found. Displacement experiments showed that hGH was an effective competitor of 125 I-labeled hGH, whereas bGH and eGH were quite inefficient. Conversely, when the tracer was 125I-labeled bGH, both bGH and eGH were good displacers, while the human hormone was poor. The values of the...
Zakin MM, Peña C, Poskus E, Stewart JM, Paladini AC.The immunological properties of a synthetic human growth hormone fragment comprising the amino acids 73 through 128 and of the homologous natural horse growth fragment formed by amino acids 73 through 123, have been comparatively studied. Antisera obtained in rabbits inoculated with the native human hormone or with the fragments, were used. By hemagglutination experiments both fragments have the same reactivity toward the anti-human growth hormone serum, but complement fixation curves detect the existence of at least two populations of antibodies presumably originated against the sequence 73-1...
Daurat-Larroque ST, Portuguez ME, Santomé JA.Bovine and equine growth hormones were chemically modified with tetranitromethane, at pH 7.4 during 5 h and at pH 8.0 in the presence of 8 M urea during 1 h. a) Both hormones have very similar but not identical reactivities. b) The nitration of the reactive tyrosines and tryptophan residues at pH 7.4 produces no detectable changes in their immunological or somatotrophic activities. C) The nitration of all tyrosine residues in both hormones gives rise to a complete loss of somatographic activity with no alteration of the immunological activity.
Johnson HD, Vanjonack WJ.Recent data on various environmental stressors and blood hormone patterns are presented for lactating cattle. Known stressor effects of such factors as environmental temperature, air pollution, and noise on the plasma thyroxine, growth hormone, cortisol, prolactin, progesterone, luteinzing hormone, epinephrine, and norepinephrine of lactating cattle are discussed. Information on stressor effects is lacking on glucagon, insulin, vasopressin, calcitonin, oxytocin, thyrotrophic hormone, follicle stimulating hormone, melatonin, parathyroid hormone, and estrogens in the lactating cow. The importanc...
Poskus E, Zakin MM, Fernámdez HN, Paladini AC.Peptide fragments, obtained from equine growth hormone by cyanogen bromide cleavage and further chemical treatment, were isolated and identified. Their immunological reactivities were tested by hemagglutination and complement fixation methods using rabbit antisera against native hormone. Antigenic determinants were detected in the fragments comprising amino acid sequences 5-72 and 73-123, this last one being predominant. Fragment 124-178 had very low reactivity. Nitration of peptide 73-123 did not modify its immunological properties,but oxidation diminished them. Comparison of the antigenicity...
Oliver L, Hartree AS.The cystine-containing peptides of horse growth hormone were isolated and their amino acid sequences determined. Four unique half-cystine residues occur in two peptides, one containing 11 and the other, at the C-terminus of the protein, 15 amino acids. These sequences are compared with published data on growth hormones from other species.
Saxena BB, Henneman PH.Equine growth hormone has been prepared from acetone-dried residues following extraction of gonadotropins from fresh frozen equine pituitary glands. The growth hormone appeared as a single fraction by gel filtration on Sephadex G-50 and ultracentrifugation. A sedimentation constant of 3.12 was obtained. Preliminary end-group analysis suggested phenylalanine at both aminoand carboxy-terminals. Amino acid analysis of the growth hormone was performed. Four components of equine growth hormone were separated by polyacrylamide column electrophoresis and all 4 were shown to contain growth hormone act...
Guirnalda PD, Malinowski K, Roegner V, Horohov DW.Aging has been associated with declines in somatotropin and IGF-I levels as well as declines in immune function. To determine the effects of age and whether ST administration could reverse immunosenescence in horses, eight young and eight aged female standardbred horses were given 10 mg/d recombinant equine somatotropin (eST) or vehicle buffer for 49 d. Plasma IGF-I concentrations in both age groups were higher in eST-treated animals (P < 0.001), and higher in young eST-treated mares than in aged eST-treated mares during wk 4 to 7 (P < 0.001). There was a trend toward lower monocyte and ...
Buff PR, Johnson PJ, Wiedmeyer CE, Ganjam VK, Messer Iv NT, Keisler DH.Horses fed beyond their nutritional requirement and that are physically inactive will develop obesity, which is often accompanied by insulin resistance and heightened risk of laminitis. The use of pharmacologic agents in combination with nutritional restriction may promote weight loss in obese horses unable to exercise because of laminitic pain. This study shows that reducing feed intake of brome grass hay to 75% of ad libitum intake in obese pony mares reduces body weight without induced exercise. Additional supplementation of ractopamine hydrochloride for 6 weeks resulted in a tendency for i...
Davicco MJ, Coxam V, Faulconnier Y, Dubroeucq H, Martin-Rosset W, Barlet JP.The present study was undertaken to assess GH secretory profiles in 12 light-breed foals and their dams during forty days after delivery, and the possible influence of GRF and TRH on plasma GH concentrations in these newborn foals. GH secretory pattern was pulsatile in one day- as well as in forty days-old foals. The number of secretory spikes (10 per 24 h) did not vary between days 1 and 40. In the same times, GH secretion did not show any circadian rhythm either in foals or in their dams. Mean daily plasma concentrations (measured through blood samples collected every 20 min for 24 h) were l...
Capshaw EL, Thompson DL, Kulinski KM, Johnson CA, French DD.Fourteen foals between 4 and 4.5 mo of age were used to determine the effects of 12 mo of daily treatment with equine somatotropin (eST) on growth, metabolic, and hormonal characteristics. The foals were paired by sex, type, and lineage, and one of each pair was administered eST daily at 20 microg/kg of BW. Body weights, body measurements, and assessments of glucose tolerance and feedback effects on endogenous somatotropin (ST) secretion were made routinely. Treatment with eST did not alter (P > 0.10) BW, height at withers, length of body, widths of chest and rump, heart girth, length of he...
Dart AJ, Strong M, Rose RJ, Hodgson DR.To evaluate the clinical, haematological, and serum biochemical effects of two large doses of recombinant equine growth hormone. Methods: Duplicated Latin square. Methods: Three Thoroughbred and three Standardbred mares aged between 12 and 17 years. Methods: Two horses were randomly assigned into one of three groups. On each of three successive days, each horse pair received one of two dosages of growth hormone or a saline placebo so that by the end of the experiment all three horse pairs had received both dosages and the saline placebo. Dose rates selected were 50 micrograms/kg, and 100 micro...
Pruett HE, Thompson DL, Cartmill JA, Williams CC, Gentry LR.Light horse mares, stallions, and geldings were used to 1) extend our observations on the thyrotropin releasing hormone (TRH) inhibition of GH secretion in response to physiologic stimuli and 2) test the hypothesis that stimulation of endogenous TRH would decrease the normal rate of GH secretion. In Exp. 1 and 2, pretreatment of mares with TRH (10 microg/kg BW) decreased (P < 0.001) the GH response to exercise and aspartate infusion. Time analysis in Exp. 3 indicated that the TRH inhibition lasted at least 60 min but was absent by 120 min. Administration of a single injection of TRH to stal...
Curcio Bda R, Pereira GR, Antunes LI, Boff AN, dos Santos FC, Lucas T, Nogueira CE, Corcini CD, Liu I, Deschamps JC.In vitro fertilization (IVF) procedures are limited by the inability to mature equine oocytes on in vitro methods. Objective: The aim of this study was to evaluate structural integrity of equine oocytes subjected to vitrification with a synthetic polymer (PVA). Methods: The effect of eGH and its relationship with IGF-I on in vitro maturation (IVM) were evaluated. Compact cumulus oocytes complexes (n=122) were cultured in TCM-199 with eGH, IGF-I or eGH+IGF-I for 30h at 38.5C in air with 5 % CO2. Oocytes were fixed after IVM or subjected to the vitrification protocol. Cryopreserved oocytes were ...
Champion ZJ, James EA, Vickers MH, Breier BH, Casey PJ.The effect of intramuscularly administered recombinant bovine growth hormone (rbGH) on insulin-like growth factor-I (IGF-I) and white and red blood cell indices was studied in Thoroughbred geldings. An insulin-like growth factor binding protein (IGFBP)-blocked radioimmunoassay was modified and validated for the measurement of IGF-I in equine blood plasma. Baseline values of IGF-I and blood indices were determined over a 48 h period and then a single dose of 5 microg/kg, 10 microg/kg or 50 microg/kg of rbGH was administered. Insulin-like growth factor-I levels increased in a dose-dependent mann...
Mollerach-Gobbi B, Retegui LA, Peña C.The immunochemical behavior of several fragments of equine growth hormone (eGH) was examined using competitive binding assays with antibodies (Abs) to eGH obtained from different sources. Antigenicity was detected within the sequences 5-72 and 73-123 by rabbit Abs to eGH and by three mouse monoclonal antibodies (MAbs) produced by using bovine growth hormone as immunogen, but showing heteroclitic properties towards eGH. The polyclonal Abs to eGH also recognized as immunoreactive two smaller peptides corresponding to the amino acid residues 52-72 and 110-123. By contrast, the heteroclitic Abs to...
Bakst M, Hadick S, Proudman J, Maruyama K.This study was conducted to determine the crossreactivity of antisera to human prolactin (PRL), adrenocorticotropic hormone (ACTH), and growth hormone (GH) to turkey pituicytes. In addition, crossreactivities of the above antisera and antiserum to turkey GH to pituicytes of turkey, cat, rabbit, horse, owl monkey, and human were evaluated. Results of the immunocytochemical localizations showed that with one exception antisera to human hormones were positive for each species tested. Turkey pituicytes failed to crossreact with antiserum to human GH. Likewise, antiserum to turkey GH failed to cros...
Sandusky GE, Wightman KA.Specific cell populations in the pituitary glands of the rat, cat, pig, and human being were positive for thyroid-stimulating hormone (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). When reacted with prediluted rabbit anti-human TSH, LH, and FSH, antisera were not positive for the demonstration of these hormones in the horse, cow, or dog. Immunocytochemical staining was obtained in the horse, cow, and dog by the use of a primary antiserum against a specific beta-subunit of bovine TSH. The immunocytochemical staining of TSH, LH, FSH, adrenocorticotropic hormone, growth ...
Viljanto M, Cutler C, Taylor P, Habershon-Butcher J, Gray B.MK-0677 (ibutamoren) is an orally active non-peptide growth hormone secretagogue that binds to the ghrelin receptor stimulating the secretion of endogenous growth hormone. It is one of the most prevalent performance-enhancing compounds currently available online and is potentially subject to abuse both in human and equine sports. The aim of the current study was to investigate whether it could be detected in equine hair following oral administration of MK-0677 mesylate to a Thoroughbred racehorse. MK-0677 and its O-dealkylated metabolite were extracted using an existing method for prohibited s...
Kennedy SR, Thompson DL, Pruett HE, Burns PJ, Deghenghi R.A series of experiments was performed to determine the factor(s) responsible for an apparent inhibition of GH secretion in mares administered the GH secretagogue EP51389 in combination with GnRH, thyrotropin-releasing hormone (TRH), and sulpiride. Experiment 1 tested the repeatability of the original observation: 10 mares received EP51389 at 10 microg/kg BW; five received TRH (10 microg/kg BW), GnRH (1 microg/kg BW), and sulpiride (100 microg/kg BW) immediately before EP51389, and five received saline. The mixture of TRH, GnRH, and sulpiride reduced (P = 0.0034) the GH response to EP51389, con...
Nadal MR, Thompson DL, Kincaid LA.Two experiments were conducted to determine 1) the prolactin response to different kinds of feedstuffs in stallions and 2) the effects of total feed deprivation on prolactin secretion in mares and its interaction with the prolactin response to feeding. Experiment 1 was performed with stallions as a 6 x 6 Latin square: A) no feed; B) pelleted feed fed to meet 82.5% of the horses' CP requirements; C) pelleted feed at 25% of the amount in B; D) pelleted feed as in B plus water ad libitum; E) cracked corn at the weight in B; and F) chopped alfalfa at the weight in B. The positive prolactin respons...
Rahmanian MS, Thompson DL, Melrose PA.The ultrastructural and immunoreactive staining characteristics of cells containing prolactin (lactotropes) and growth hormone (GH; somatotropes) in the anterior pituitaries of gonadally intact pony mares were studied at the electron microscopic level. Lactotropes included two morphological subsets: Type I cells were larger and contained large, dense, polymorphic granules that were scattered throughout the cytoplasm; Type II cells were smaller and contained small, dense, polymorphic granules that were predominantly found in peripheral areas of the cytoplasm. Lactotropes constituted 5 to 16% of...
Laidler P, Cowan DA, Houghton E, Kicman AT, Marshall DE.Recognition by the legal authorities that growth hormones (GHs) may be abused to improve sporting performance and/or physique has led to the implementation of controls that make it an offence to produce, supply, possess or import and export GHs, with intent to supply, without the authority to do so. A method is described for the discriminatory analysis of human, equine, porcine and bovine GHs for forensic purposes. Peptide-mass mapping by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry following tryptic digestion gave sequence coverages of 97.4%, 93.7...
Melchert M, Aurich J, Ertl R, Reichart U, Walter I, Gautier C, Kaps M, Aurich C.Mares resume ovarian activity rapidly after foaling. Besides follicle-stimulating hormone (FSH) and luteinizing hormone (LH), the pituitary synthesizes prolactin and growth hormone which stimulate insulin-like growth factor (IGF) synthesis in the liver. We tested the hypothesis that follicular growth is initiated already antepartum, mares with early and delayed ovulation differ in IGF-1 release and that there is an additional IGF-1 synthesis in the placenta. Plasma concentrations of LH, FSH, IGF-1, IGF-2, activin and prolactin. IGF-1, IGF-2, prolactin and their receptors in placental tissues w...
Conrad MB, Leatherwood JL, Paris BL, George JM, Martinez RE, Vergara-Hernandez FB, Nielsen BD, Colbath AC, Arnold CE, Glass KG, Welsh TH, Bradbery AN.Extra-label bisphosphonate (BP) use in juvenile horses is anecdotally reported, primarily for analgesic effects, despite the limited scientific understanding of biologic impacts on skeletally immature horses undergoing exercise. The objective of this study was to determine the effects of clodronate disodium (CD), a form of BP, on endocrine regulators of calcium. Thus, 32 yearling Quarter Horses were stratified by age (500 ± 13 d), body weight (BW; 336 ± 26 kg), sex (n = 16 geldings, n = 16 fillies), and initial bone optical density into 1 of 4 treatment groups for a 168-d tr...
Satué K, Fazio E, Velasco-Martínez MG, Barbiera G, La Fauci D.Growth hormone (GH) influences follicular development mainly by stimulating insulin-like growth factor 1 (IGF-1), which acts systemically and locally within the ovary. However, the metabolic profile of follicular fluid (FF) in mares, particularly markers such as fructosamine (FRUCT), an indicator of glucose metabolism, remains poorly characterized. This study aimed to evaluate GH, IGF-1, and FRUCT concentrations in plasma and FF and their variation across follicle sizes. Sixty ovaries were collected during the breeding season from 30 clinically normal mares raised for meat production. Blood sa...
Shimizu Y, Sugai-Bannai M, Tanabe H, Saito K, Ito H, Tokushige H, Kamiya K, Hirano-Kodaira M, Yamada M, Leung GN.Somapacitan is the second generation of recombinant human growth hormone (rhGH) medication that retains the pharmacological effects of rhGH but exhibits a longer duration of action due to its reversible albumin-binding in the body. In general, the use of all recombinant growth hormone (rGH) analogues is banned by the human and animal sports regulatory authorities due to their anabolic and lipolytic effects. However, little is known about the elimination kinetics and biological effects of the newly introduced long-acting rhGH, somapacitan, in horses. This paper describes the administration stud...
Barnabé A, Loup B, Cawley A, Delcourt V, Garcia P, Popot MA, Keledjian J, Bailly-Chouriberry L.Despite the International Federation of Horseracing Authorities (IFHA) regulation associated with heavy sanctions, the abuse of prohibited substances must be identified and deterred throughout horses' athletic careers, such as the administration of recombinant growth hormone (rGH). GH is naturally produced in mammal organisms to stimulate growth. Thus, rGH administration can enhance the performance of horses by expanding some physical abilities. As measuring endogenous GH levels is complex, an indirect strategy is to monitor GH-associated biomarkers in plasma as insulin-like growth factor 1 (I...
Ivanković A, Pećina M, Bittante G, Amalfitano N, Konjačić M, Kelava Ugarković N.Local horse breeds, particularly cold-blood types, are often marginalized in economic and social contexts, primarily due to the neglect of their economic, genetic, and cultural potential, as well as their role in preserving the identity of rural areas, local communities, and ecosystems. The valorization of these breeds is a crucial prerequisite for their economic repositioning. The Croatian Posavina horse is a local breed, well adapted to harsh, extensive production systems. Its sustainability is achieved through pasture-based meat production, primarily targeting foreign European markets. Ensu...
Shimizu Y, Sugai-Bannai M, Saito K, Hirano-Kodaira M, Leung GN.Somapacitan, a long-acting growth hormone derivative, and recombinant human growth hormone (rhGH) are protein-based drugs generally used to treat growth disorders and GH deficiency in humans. Due to their potential to enhance the horse performance, the use of these drugs is prohibited at-all-times by the International Federation of Horseracing Authorities for horseracing and the Fédération Equestre Internationale for equestrian sports. In this study, we developed a test method for the identification and differentiation of somapacitan and rhGH in equine plasma by using liquid chromatography h...
