Hormone
Function
Thyroxine (T4) - carries 4 iodine atoms)
Regulation of metabolism and growth
Triiodothyronine (T3) - carries 3 iodine atoms)
Regulation of metabolism and growth
Reverse-triiodothyronine (r-T3) - formed by peripheral conversion of T3
Metabolically inactive
Calcitonin
Regulation of calcium and phosphate levels (lowers serum levels through deposition in bone and renal excretion)