Background: The diagnosis of primary hypothyroidism in the elderly hospitalized patients is diffi cult because of lack of classic symptoms and signs, especially when it is concurrent with other non-thyroid illnesses. The purpose of this analysis was to identify the infl uence of age on the clinical characteristics of hospitalized patients with hypothyroidism. Methods:Using the database of a medical center in northern Taiwan, 121 adult inpatients with newly diagnosed primary hypothyroidism were enrolled from January 1, 1999 to December 31, 2006. The patients were divided to two groups, group A were aged ≤ 75 years and group B were aged > 75 years. The initial clinical presentations, laboratory data, diagnoses at admission and discharge, and outcomes were analyzed. Results: Our population consisted of 77 males and 44 females,
and the mean age was 73 years. The patients were most often diagnosed in the division of cardiology (36.4%), and 71.1% had coexistent heart diseases. The percentage of diagnosis in hypothyroidism after thyroid screening was signifi cantly improved in group A (p=0.012) but not group B (p=0.121).The percentage of diagnoses of heart and neuro-mental diseases
at discharge were signifi cantly decreased when compared to at admission. The mean duration of hospitalization and rate of coexistent heart diseases and 2-year follow-up mortality were signifi cantly higher in group B than group A. The main factors associated with 2-year mortality in the hospitalized patients with hypothyroidism were ages and hyponatremia.Conclusion: Hospitalized patients with primary hypothyroidism may present as heart or neuromental diseases. Ages and
hyponatremia attributed to 2-year mortality in the hospitalized patients with hypothyroidism.