Ethionamide-induced goitrous hypothyroidism.

A 42-year-old woman developed goitrous hypothyroidism while receiving ethionamide for treatment of an atypical mycobacterial infection. Five weeks after discontinuation of ethionamide therapy, thyroid function had returned to normal. The goitrogenic effect was studied in vitro by incubating ethionamide in various concentrations (10(-3) to 10(-7) mol/L) with ovine thyroid cells in tissue cultures. Ethionamide inhibited the trapping of technetium and organification of iodine at concentrations seen clinically (10(-5) mol/L). Ethionamide appears to be a potential goitrogen in susceptible persons.