Hyperthyroidism and propylthiouracil-induced agranulocytosis during chronic lithium carbonate therapy

The authors describe the case of a 49-year-old woman who developed a goiter, mild symptoms of hyperthyroidism, and grossly elevated thyroid function tests after 2 years of treatment with lithium carbonate. Thyroid microsomal autoantibodies were also present. She was retreated with propylthiouracil and improved, but within 3 months she developed agranulocytosis. Propylthiouracil was discontinued, and the patient was treated with antibiotics and recovered. She was then given 131I to control her hyperthyroidism. The case is an example of the rare association of hyperthyroidism with lithium, which usually suppresses thyroid function, and demonstrates that lithium carbonate cannot prevent agranulocytosis caused by propylthiouracil.