Thyroid

• T4 = thyroxine: two T2 molecules join to form T4
• T3 = triiodothyronine: one T1 and one T2 join to form T3.
• thyroid hormones (T4 and T3):  

  stimulate use of cellular oxygen to produce ATP. 

  stimulate synthesis of Na+ / K+ pumps. 

  increase heat generated. 

  increase protein synthesis, lipolysis, cholesterol excretion. increase use of glucose & fatty acids for ATP production. enhance some actions of norepinephrine & epinephrine. accelerate body growth – particularly of nervous tissue. 
• calcitonin: Can decrease blood calcium. 

  inhibits osteoclasts.