[Exacerbation of autoimmune hypothyroidism after hemi-hypophysectomy in a patient with Cushing's disease].

A 41 year old woman affected by Cushing's disease underwent hemi-hypophysectomy with removal of an ACTH secreting microadenoma. Forty days later, when normal ACTH, cortisol plasma levels and urinary cortisol levels were restored, features of primary autoimmune hypothyroidism developed. While cortisol levels were elevated serum thyroid hormone levels were normal, serum hormone TSH was at the upper limit of the normal range and serum antimicrosomal antibodies were slightly elevated. It is likely that hypothyroidism already present before surgery was not clinically evident due to the immunosuppressive effect of high cortisol levels. The need to assess thyroid function in patient with hypercortisolism is emphasized with the aim to identify the possible onset of autoimmune thyroid disease when cortisol levels are normalized.