Ramiro Toribio


Professor; Equine Ambulatory Service Section Head


toribio.1@osu.edu (614) 614-292-6661 Veterinary Medical Center
601 Vernon Tharp Street
Columbus, OH 43210
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Veterinary Clinical Sciences


  • Equine

Professional Training and experience

  • PhD, The Ohio State University, Equine Endocrinology, 2001
  • Diplomate, American College of Veterinary Internal Medicine, 1999
  • MS, Universidad Nacional de Costa Rica, Costa Rica, Animal Endocrinology, 1993
  • DVM, Universidad Nacional de Rio Cuarto (Honors), Argentina, 1988
  • BS, Mexico-Panama Technological Institute (Honors), Panama, 1982

Research Interests

  • Equine Endocrinology
  • Equine calcium regulation during health and disease:
    • Pathogenesis of hypocalcemia during sepsis and endotoxemia
    • Parathyroid gland function in healthy and diseased horses
    • Transepithelial calcium transport
    • Mechanisms of hypercalcemia in horses
    • Molecular aspects of calcium regulation in horses
  • Animal Models of Bone Development:
    • Genetic manipulation of the PTHrP gene in mice
    • Importance of the PTHrP gene in osteoblast differentiation and function

Research Programs

Endocrinology Research Program

Bronze statue of horseThe Equine Endocrinology Research Program of The Ohio State University has the mission of investigating endocrine regulation and dysregulation in healthy and diseased horses and foals, with emphasis to in clinically relevant problems. Thanks to the support of the College, staff, students, private industry, friends, and various funding agencies, important discoveries in this area have been made.
Areas of Research

    Calcium and magnesium regulation
    Endocrine dysregulation in critically ill horses and foals
    Comparative Endocrinology of Bone Biology


    Ramiro Toribio (Program Leader)
    Catherine Kohn


    Dr. Eason Hildreth (PhD student)
    Holly Brown (Student)
    Krista Hernon (Student)
    Brandy Marlow (Research assistant)
    Feifei Wang (PhD student)
    Kasia Dembek (Resident, MS student)
    Kate Onasch (Student)
    Alicia Griffin (Student)
    Melinda Himler (Student)


Our laboratory is equipped with state of the art equipment (PCR systems, imaging systems, microtomography, histology,) and has access to other shared instruments and research support cores within the College and the University.

Calcium and Magnesium Regulation
Calcium and Magnesium Regulation

Closeup of horse eyeDisorders of calcium and magnesium regulation are frequent in critically ill horses and foals. Both hypocalcemia and hypomagnesemia are associated with neuromuscular dysfunction, excitability, ileus, cardiac arrhythmias, and death in horses. For the past 10 years we have been actively working in this field, in particular on parathyroid hormone (PTH) and calcitonin physiology and pathophysiology. Important discoveries have been made (see selected publications). We have found that horses with gastrointestinal diseases often develop severe calcium and magnesium derangements result of low PTH concentrations (parathyroid gland dysfunction). In septic foals, we discovered that abnormally high PTH concentrations were associated with mortality. Sepsis is the number one cause of foal mortality. Our results have provided insight on the endocrine aspects of diseased horses and foals.
Selected Publications

    Toribio RE, Kohn CW, Rourke KM, Levine AL, Rosol TJ. Effects of hypercalcemia on serum concentrations of magnesium, potassium, and phosphate and urinary excretion of electrolytes in horses. Am J Vet Res. 2007;68:543-554.
    Toribio RE, Kohn CW, Hardy J, Rosol TJ. Alterations in serum parathyroid hormone and electrolyte concentrations and urinary excretion of electrolytes in horses with induced endotoxemia. J Vet Intern Med. 2005;19:223-231.
    Toribio RE, Kohn CW, Leone GW, Capen CC, Rosol TJ. Molecular cloning and expression of equine calcitonin, calcitonin gene-related peptide-I, and calcitonin gene-related peptide-II. Mol Cell Endocrinol. 2003;199:119-128.

Insulin resistanceDiagram of Calcium and Magnesium Regulation

Comparative Endocrinology of Bone Biology

Figure showing PTHrPUnderstanding bone biology as it relates to human and animal health is critical for the development of novel therapeutic approaches to various skeletal diseases. We have been using various strategies to study the role of the parathyroid hormone-related peptide (PTHrP) gene in the commitment of bone marrow stem cells to become bone cells (osteoblasts). Information from these studies could have potential applications in fracture repair, osteoporosis, and cancer-associated bone disease.


    Toribio RE, Brown HA, Novince C, Rosol TJ et al. The mid-region, nuclear localization sequence and C-terminus of PTHrP regulate skeletal development, hematopoiesis, and survival in mice. FASEB J. 2010;24:1947-1957.

Endocrine Dysregulation
Endocrine Dysregulation in Critically Ill Horses and Foals

Ill horseSepsis, defined as the presence of pathogenic organisms or their toxins in blood or tissues, is the number one cause foal mortality. Although major improvements in treating septic foals have been made in recent years, there is limited information on endocrine dysregulation during this pathological condition in foals. To address specific questions in this field, we have established a research program to study various endocrine factors that we believe are relevant to the pathogenesis of sepsis in foals. Areas under study include the hypothalamus-pituitary-adrenal axis, calcium metabolism/parathyroid hormone, and the energy metabolism (glucose, leptin, insulin).
Selected Publications

    Hurcombe SD, Toribio RE, Slovis N, Kohn CW, Refsal K, Saville W, Mudge MC. Blood arginine vasopressin, adrenocorticotropin hormone, and cortisol concentrations at admission in septic and critically ill foals and their association with survival. J Vet Intern Med. 2008;22:639-647.
    Barsnick RJ, Hurcombe SD, Smith PA, Slovis NM, Sprayberry KA, Saville WJ, Toribio RE. Insulin, glucagon and leptin in critically ill foals. J Vet Intern Med 2010; Nov 23. [Epub ahead of print]
    Hurcombe S, Toribio RE, Slovis N et al. Calcium regulating hormones and serum calcium and magnesium concentrations in septic and critically ill foals and their association with survival. J Vet Intern Med 2009; 36:197-201.