Toxic agents present in food which interfere with thyroxine synthesis lead to the development of
1. toxic goitre
2. cretinism
3. simple goitre
4. thyrotoxicosis

The thyroid hormone that has the most potent effect on increasing metabolic rate would be:
1. thyroxine
2. thyroglobulin
3. triiodothyronine
4. thyrocalcitonin