Thyroid and Parathyroid Glands

Abstract

The two lobes of the human thyroid are bridged by the thyroid isthmus tissue. Each thyroid follicle is encased by a single layer of functionally-polarized epithelial cells. The follicles are filled with a proteinaceous colloid that hold the store of the small amine thyroid hormones before they are enzymatically ‘plucked’ and released in to the circulation. Thyroid hormones have a general, priming, metabolic effect on virtually all cells in the body. Perhaps we could view physiologic levels of thyroid hormones as providing the cruise control of various body functions. Hypothyroidism leads to lethargy, slows mentation and reflex time is longer whereas hyperthyroidism increases cell metabolism, appetite is stimulated, anxiety and irritability can be heightened.