Carum induced hypothyroidism: an interesting observation and an experiment

Carum carvi is a widely available herb that has been used as a food additive and as a medication in traditional medicine for many years. Its potential biological effects include analgesic, anti-inflammatory, anti-anxiety and antispasmodic activities. We report a patient with papillary thyroid carcinoma who were under treatment with levothyroxine and experienced an elevated TSH level by ingestion of Carum carvi. TSH level was increased to 60.3 mIU/L with no change in levothyroxine dosage and decreased to normal range after discontinuation of the Carum carvi. Observing this dramatic change in TSH level by carum ingestion, carum carvi capsules was produced and one of the researcher tried the medication on herself with a dose of 40 mg/kg/day. She had a history of hypothyroidism and was taking 100 ugr/day of levothyroxine. TSH was markedly increased 2 weeks after ingestion of Carum carvi and returned to normal range 5 months after discontinuation of it. This case report shows the effect of consumption of Carum carvi in increasing TSH level in hypothyroid patients treating with levothyroxine. The exact mechanism of action of carum carvi remains unknown.