Notes Ch. 13c Anatomy and Physiology Endocrine System Notes Ch. 13c Anatomy and Physiology

Thyroid Gland The thyroid gland is in the throat area that is made of 2 lobes connected by an isthmus. It’s purpose is to remove iodine from the blood.

Thyroid Hormones Thyroxine and triiodothyronine affect metabolic rates. Thyroxine is call T4 because it is has 4 atoms of iodine. Triiodothyronine is called T3 because it has 3 atoms of iodine. They both regulate the metabolism of carbohydrates, enhance the rate of proteins synthesis, and stimulate the breakdown of lipids.

The last hormone produced in the thyroid is calcitonin – it controls the rate that calcium and phosphate ion concentrations. This is an important hormone during early growth – it may help increase calcium in the bones.

Parathyroid Glands These glands are on the posterior surface of the thyroid gland. There are usually 4 of them. These glands secrete a hormone that regulates the concentrations of calcium and phosphate ions in the blood.

Parathyroid Hormone Parathyroid glands secrete parathyroid hormones (PTH). This hormone increases blood calcium ion concentration and decreases blood phosphate ion concentration. It is also important for making vitamin D.

Parathyroid Gland Disorders Hyperthyroidism – too much PTH – fatigue, muscle weakness, painful joints, altered mental functions, depression, weight loss, bone weakening. Hypothyroidism – decreased PTH – muscle cramps and seizures