Lithium, thyroid function and antithyroid antibodies.

1. Lithium is known to affect thyroid function. It can cause both subclinical and overt hypothyroidism that may involve in some instances an autoimmune mechanism. 2. Sixty (60) psychiatric patients, already under treatment with lithium for at least 6 months, were administered additional thyroid tests and monitored over a one-year period to study the implication of the autoimmune system in the development of hypothyroidism and thyroiditis during lithium therapy. 3. At the beginning of the study, 16 patients presented biological hypothyroidism (laboratory values under normal limits) and only 4 of them showed some slight clinical symptoms. Initially, antithyroid antibodies were detected in 20% of the patients (6 hypothyroids and 6 euthyroids): 12 had antimicrosomal antibodies and only 8 antithyroglobulin antibodies. 4. During the study, only one additional patient (euthyroid) developed antimicrosomal antibodies. All patients with antithyroglobulin antibodies had antimicrosomal antibodies and 6 hypothyroid patients had both types of antibodies.