Objective: to analyze the factors which modify the thyroid hormone levels in domestic birds.Materials and methods: information from the last 50 years included in the BBCS-LILACS, Fuente Académica, IB-PsycINFO, IB-SSCI, IB-SciELO, Scopus and Scirus, data bases 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 was found and analyzed.The information was later divided into two sections as follows: synthesis, liberation and metabolism of thyroid hormones and factors which modify the thyroid hormones levels.Conclusion: thyroid hormones production can be influenced by factors such as temperature, incubation, diet, fasting, photoperiods and stress.