A nurse manages care for a patient starting treatment with propylthiouracil for hyperthyroidism. The nurse understands that propylthiouracil acts by:
1. Blocking the iodide uptake mechanism
2. Blocks proteolysis of thyroglobulin
3. Inhibition of iodide
4. Inhibiting the coupling mechanism which forms T3 and T4 from mono- and di-iodotyrosine