PINEAL, THYROID, PARATHYROID, THYMUS

• Pineal gland - hangs from the roof of the brain's third ventricle; secrets melatonin
• Thyroid gland - found at the base of the throat; produces thyroid hormone (TH) and calcitonin
• Thyroid hormone - controls rate of oxidation of glucose to supply body heat and chemical energy
• Iodine-containing hormones that compose the thyroid hormone:

  Thyroxine (T₄) - secreted by thyroid follicles

  Triiodothyronine (T₃) - conversion of T₄ at target tissues
• Calcitonin - decreases blood calcium levels by causing calcium deposition on bone; antagonistic to parathyroid hormone
• Parathyroid Glands - tiny masses on the posterior of the thyroid; secrete parathyroid hormone (PTH)
• Parathyroid hormone (PTH) - increases calcium levels in the blood
• Thymus - located in the upper thorax, posterior to the sternum; largest in children, decreases throughout adulthood; produces thymosin
• Thymosin - matures WBCs, develops the immune system