Progoitrin is a biochemical from the glucosinolate family that is found in some food, which is inactive but after ingestion is converted to goitrin. Goitrin decreases the thyroid hormone production.
^Comprehensive Pharmacy Review, Leon Shargel, 6th edition, p1191.
Bibliography
Greer, Monte A. (20 March 1956). "Isolation from Rutabaga Seed of Progoitrin, the Precursor of the Naturally Occurring Antithyroid Compound, Goitrin (L-5-Vinyl-2-Thioöxazolidine)1". Journal of the American Chemical Society. 78 (6): 1260–1261. doi:10.1021/ja01587a052.