Thyroid Function
The thyroid is a small, butterfly-shaped gland located in the neck just below the thyroid cartilage (the Adam's apple in men). The thyroid gland produces two hormones, T4 and T3, which both work to help regulate the body's metabolism. In essence, both hormones work by stimulating cells to use more energy. This causes the cells to burn through the body's energy reserves, and use this energy to make proteins and other molecules for the cells' use. The thyroid also makes a hormone called calcitonin which helps regulate blood calcium levels by blocking the breakdown of blood and causing the kidneys to excrete excess calcium.
Hypothyroidism
Hypothyroidism is the result of the thyroid gland not producing enough T4 and T3, causing the metabolism to slow down. As a result, people with hypothyroidism may experience weight gain (from not burning enough energy), as well as feelings of fatigue and lethargy. Patients may feel cold because the burning of energy creates heat, which helps to maintain body temperature. Hypothyroidism can also cause dry skin, constipation, hair loss and irregularities in women's menstrual cycles; all normal body processes slow down due to the decreased use of energy.
Hyperthyroidism
Hyperthyroidism is the opposite of hypothyroidism in that too much T4 and T3 are produced. This causes the body to use energy faster than usual, which can cause patients to become jittery, have an elevated heart rate and develop high blood pressure. Patients may also lose weight (because they are burning more calories), and develop diarrhea and insomnia. Some patients also experience bulging of their eyes, intolerance to heat and shaking of the hands because of involuntary muscle tension. Hyperthyroidism can also cause sensitivity to light, visual problems and persistent staring (because patients may not be able to properly move their eyes).
