Thyroid dysfunction is common, especially among women over the age of 50. In caring for peri- and post-menopausal women, it is important to recognize the changing clinical manifestations of thyroid disease with age. Postmenopausal women are at increased risk of both osteoporosis and cardiovascular disease, and untreated thyroid disease may exacerbate these risks. Screening for thyroid dysfunction in asymptomatic individuals is controversial, but aggressive case-finding should be pursued, especially in older women. Women with overt thyroid dysfunction should be treated. Therapy for women with subclinical thyroid dysfunction is more controversial, although women with levels of thyroid stimulating hormone (TSH) > or =10 mU/L should be treated, and treatment may be considered in symptomatic women with subclinical hypothyroidism and TSH values <10 mU/L, and in women with subclinical hyperthyroidism who have TSH values consistently <0.1 mU/L. In women who are treated with thyroxine, careful dose titration and monitoring are required in order to prevent the adverse consequences of iatrogenic subclinical hyperthyroidism or hypothyroidism. Finally, caution is required in diagnosing and treating thyroid dysfunction in women who are taking oral estrogens or selective estrogen receptor modulators.