A 53 year-old woman with a 10-days history of upper respiratory tract infection and had fever which relapsed within 3 days was diagnosed to be subacute thyroiditis by clinical story, increased sedimentation rate (112 mm/h), decreased radioactive iodine uptake and by biopsy confirmation. Her typical neck pain regressed within 5 days. Although thyroidal function tests were expected to be hyperthyroid, they were; free-T3: 2.41 pg/ml (1.45-3.48), free-T4: 0.77 ng/dl (0.71-1.85), TSH: 0.039 µIU/ml (0.49-4.67), and antimicrosomal antibody: 35.96 IU/ml (<20). Her indefinite symptoms of hypothyroidism became evident during the last 1-2 years and her menses stopped when she was 35 years old. When her basal and stimulated pituitary hormone levels were evaluated, all of the pituitary hormones except ACTH were found to be insufficient. Pituitary MRI revealed total empty sella.

Her clinical story was not typical for Sheehan's syndrome. Although the positivity of antimicrosomal antibody can be due to subacute thyroiditis it can also suggest that hypopituitarism in this patient is probably related with lymphocytic hypophysitis. Free-T4 was in the lower normal limit due to the release of minimal reserve hormone after thyroidal tissue destruction. Replacement therapy was given to her one month later, because of free-T4 value was decreased. A case of subacute thyroiditis that can otherwise be an outpatient was found to have hypopituitarism as a result of the careful evaluation of thyroidal function tests.