Sex related goitrogenic effect of lithium carbonate in healthy young subjects.

Eight healthy males and 8 healthy females without a family history of thyroid disease or detectable thyroid autoantibodies were given 300 mg of lithium carbonate twice a day for 28 days. Using a precise and accurate ultrasonic technique we demonstrated an increase in median thyroid volume from 18 ml on day 0 to 34 ml on day 28 (P less than 0.005) in the female group, whereas the median thyroid volume was unchanged in the male group. A significant increase in basal serum TSH level and serum TSH levels 20, 60 and 90 min after 200 micrograms of TRH iv was found in both groups after 28 days of lithium treatment. The means of the individual TSH increments during the TRH test were not significantly different between the two sexes neither before nor after lithium treatment. After 14 and 28 days a significant fall in serum T4 levels was found in both sexes. 131I uptake (24 h) in the thyroid gland was increased in both sexes, but only in the male group was the mean PB131I (24 h) significantly reduced after 28 days of lithium treatment. In conclusion the present study suggests a difference in susceptibility of the thyroid gland to the growth stimulating effect of minute increments in serum TSH in young healthy males and females given lithium carbonate.