L2.3.4: Thyroid Gland

• THYROID GLAND

  ● Location: found at the base of the throat, inferior to the adam’s apple

  ● Consists of 2 lobes and a connecting isthmus

  ● Follicles are hollow structures that store colloidal material

  ○ Thyroid hormone is derived from this colloid

  ● Hormones produced: THYROID HORMONE and CALCITONIN
• ○ THYROID HORMONE

  ■ Major metabolic hormone

  ■ Controls rate of oxidation of glucose to supply body heat and chemical energy (ATP)

  ■ Needed for tissue growth and development

  ■ Composed of 2 active iodine-containing hormones
• ○ THYROID HORMONE

  Thyroxine (T4): Secreted by thyroid follicles

  Triiodothyronine (T3) : Formed from the conversion of T4 at target tissues
• ○ CALCITONIN

  ■ A hypocalcemic hormone

  ■ Decreases blood calcium levels by causing calcium deposition on bone

  ■ Released in response to rising blood calcium levels

  ■ Antagonistic to parathyroid hormone

  ■ Produced by parafollicular cells found between the follicles