The thyroid gland, which is part of the endocrine system, synthesizes and stores hormones that are essential to the function of every cell in the body. Located in the lower portion of the neck, the thyroid glands has a butterfly shape;the two lobes are joined in the center. Thyroid hormones regulate heart rate, blood pressure, body temperature and the rate that digested food is converted to energy. Problems with the thyroid gland are caused either because of overactivity (hyperthyroidism) or underactivity (hypothyroidism).
Changes in Metabolism
Thyroid hormones metabolize fats and carbohydrates into energy. Symptoms of hypothyroidism begin with fatigue and sluggishness. These signs can be overlooked and attributed to growing older. The Mayo Clinic says that as metabolism slows a person becomes increasingly sensitive to the cold, has unexplained weight gain, muscle tenderness, weakness, aches, and joint pain and stiffness. Hyperthyroidism also causes fatigue and muscle weakness. Additional signs of an overactive thyroid gland are increased sensitivity to the heat, sudden weight loss despite an increased appetite or normal appetite, and tremors in the hands and fingers.
Changes in Heart Rate
Thyroid hormones affect the cardiovascular system by increasing heart rate, contraction of heart muscle and cardiac output. They stimulate widening of blood vessels to ensure adequate blood flow to organs in the body. A rapid heart rate, high blood pressure, irregular heart rhythms and palpitations are symptoms of an overactive thyroid gland. Conversely, a low pulse rate indicates an underactive thyroid gland.
Body Changes
Physical changes of hypothyroidism include hair loss; dry, brittle hair; and dry, flaky skin. A person’s voice becomes hoarse in the absence of a sore throat, body temperature is consistently below normal and an enlarged thyroid gland is visible. An enlarged thyroid gland (referred to as a goiter) is also a sign of hyperthyroidism. Sometimes, an overactive thyroid gland causes the eyes to protrude and become red and swollen. A person experiences excessive tearing in one or both eyes, sensitivity to the light and blurred vision.
Effects on the Reproductive System
Abnormal menstrual cycles and a decrease in libido for both men and women are signs of hypothyroidism. Women experience difficulty conceiving. An overactive thyroid gland causes irregular menstrual patterns or the absence of a period. Hyperthyroidism can cause breast development in men, according to Medline Plus.
