Intro | Anterior Pituitary | Adrenal Glands | Ovaries | Pancreas | Posterior Pituitary | Testes | Thyroid
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
The Thyroid Gland is located at the front of the throat. It produces and secretes hormones that increase body metabolism, or the rate at which chemical reactions take place in the body.
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The thyroid gland is named after its appearance, resembling a shield. It produces and secretes two primary hormones, thyroxine (T4) and triiodothyronine (T3), when stimulated by thyroid-stimulating hormone from the anterior pituitary. These two hormones increase the overall metabolic rate (catabolic or body building chemical reactions) with the net effect of body growth and maturation. Cellular respiration and oxygen utilization are increased, body heat is increased, muscle tone is enhanced, and the force of heart rate is increased by the thyroid hormones.
Thyroid abnormalities may result in either excessive (hyperthyroidism) or reduced (hypothyroidism) levels of T3 and T4, with striking effects on the person's ability to function. Thinking and activity may reach manic levels in the former, whereas such functions become lethargic in the later.