In elderly patients, thyroid diseases may remain undiagnosed due to the lack of specificity of the clinical presentation. Thyroid function alterations seem to be more common in older persons than in adults. The aim of our study was to evaluate the incidence of thyroid function alterations in 300 elderly patients admitted to the division of Internal Medicine of the local hospital in Levanto, in a one-year period. Thyroid function alterations were discovered in 12.6% of the patients and considering the group of patients in whom a thyroid function alteration was demonstrated, 45% of them were affected by hypothyroidism (10.7% overt primary hypothyroidism, 28.9% sub-clinical hypothyroidism, 5.4% hypothyroidism secondary to hypopituitarism), 15.6% by hyperthyroidism (overt 7.8% , subclinical 7.8%), and 39.4% showed a low T3 syndrome. Our data confirm the high incidence of previously unrecognized thyroid diseases in the elderly patients admitted to an hospital and the profit that these patients can receive from the appropriate diagnosis at the admission and justify the cost of routine testing for FT4 and TSH in every person at hospital admission.