Thyroid
- Iodine-containing hormones produced by the thyroid gland
- Thyroxine (T4)
- secreted by the follicular cells of the thyroid gland
- transported in blood
- 99.95% is protein bound
- primarily to thyroxine-binding globulin (TBG)
- lesser extent to transthyretin and serum albumin.
- prohormone and reservoir for active thyroid hormone triiodothyronine (T3)
- converted as required in the tissues by deiodinases.
- Type II deiodinase converts T4 into T3.
- Triiodothyronine (T3)
- one less iodine atom per molecule than Thyroxine
- most powerful thyroid hormone
- produced in smaller quantity
- Thyroxine (T4)
- Increases metabolic activities of virtually all tissues of body
- influences physical development
- Regulates brain, nerve, muscle function
- Stimulates nearly all aspects of carbohydrate metabolism
- Increases uptake of glucose by cells
- Enhanced glucolysis
- Enhanced gluconeogenesis
- Increased rate of absorption from GI tract
- Decreases cholesterol, phospholipids, and triglycerides in plasma
- Increases free fatty acids
- Extreme levels cause high basal metabolic rates
Calcitonin
- Parathyroid hormone
- Regulates blood calcium levels by effects on bone modeling