Objective: To carry out an update on equines hypothyroidism.Material and Methods: Available literature from the last 50 years included in the BBCS-LILACS, Fuente Académica, IB-PsycINFO, IB-SSCI, IB-SciELO, Scopus and Scirus, data base as well as historical articles, texts and references cited in work published to date were analyzed.Results: Important information related to the objectives proposed in the present review were found and analyzed.It was then divided in seven sections as follows: etiology, clinical signs, diagnosis, factors which alter the diagnostic tests, no thyroid disease syndrome, prevention and treatment.Conclusion: Hypothyroidism is one of the most common alterations in equines; clinical signs are very