Background: Mood disorders also known as affective disorders include unipolar and bipolar disorders. Manic-depressive disorder, more contemporary identified as bipolar disorder, is a chronic and complex disorder. Mood stabilizers and antipsychotics are the mainstay of acute treatment for bipolar mania and depression. Lithium is the gold standard for treating bipolar disorder. Methodology: A narrative review was carried out through various databases from January 2009 to November 2021; the search and selection of articles was carried out in journals indexed in English. Keywords were used: Thyroid; lithium; bipolar; Thyroiditis; Goiter; Hypothyroidism. Results: Lithium is abundantly present at the thyroid level, the uptake of iodine being reduced. Causing as a collateral effect the increase in TSH, increasing uptake. These various alterations caused by lithium can lead to developing goiter and hypothyroidism, being the most frequent. Conclusions: This review offers an updated approach to the pathophysiological mechanisms caused by lithium as well as the main alterations produced by it.