Hypothyroidism, the most common disorder of thyroid function is especially common in the adult female population. The disease affects every major organ system and metabolic process. The diagnosis of primary hypothyroidism can be perplexing to the clinician because of its insidious onset and wide array of nonspecific manifestations. Complaints of fatigue, muscle weakness, lethargy, and weight gain are often at first attributed to emotional or other health problems. Additionally, patients may not seek medical care because they are unaware that they are ill. Clinicians need to be familiar with the signs and symptoms of hypothyroidism so that a timely diagnosis and treatment can be initiated. This article reviews the etiology, pathophysiology and clinical manifestations of hypothyroidism as well as the methods of diagnosis and treatment. Elements of patient education are described with particular emphasis on the chronic nature of hypothyroidism and the need for life long treatment.