Hypothyroidism is a condition in which the thyroid does not produce enough hormones. This condition occurs mostly in women over the age of 50. If left untreated it can lead to numerous health conditions such as obesity, infertility, and joint problems. Hypothyroidism can be congenital:
Approximately one in 3,000 babies in the United States is born with a defective thyroid gland or no thyroid gland at all. In most cases, the thyroid gland didn't develop normally for unknown reasons, but some children have an inherited form of the disorder. Often, infants with congenital hypothyroidism appear normal at birth. That's one reason why most states now require newborn thyroid screening.
Hyperthyroidism is a condition in which the thyroid produces too much thyroxine, which a hormone. Some symptoms of hyperthyroidism include weight loss, rapid heart beat, and nervousness. Graves disease is the most common cause of hyperthyroidism. Scientists are not exactly sure what causes Graves Disease but it thought that people who have this disease have a genetic predisposition.
I agree with the previous responder that hyperthyroidism and hypothyroidism can have a genetic basis. There is also the autoimmune form of hypothyroidism and hyperthyroidism. An autoimmune disease occurs when the body's immune response mistakes a person's body part as a foreign agent and attacks it. When this occurs to the thyroid the diseases are called Graves Disease (hyperthyroidism) and Hashimoto's Disease (hypothyroidism). The cause of these diseases are unknown. Many believe that there is a trigger, such as a virus or bacterial infection, and the body's immune response overreacts and begins targeting a specific body part. These diseases are chronic and at times acute.
Hyperthyroidism and hypothyroidism are endocrine disorders that alter the normal metabolic rate. Hyperthyroidism is due to oversecretion of the thyroid hormones(thyroxine,triiodothyronine) and causes glucose to be burned by the body at an increased rate. People with hyperthyroidism tend to lose body weight,have increased hunger, show protrusion of the eyeballs(exophthalmia), be irritable, and suffer from tachyarrythmias. These people may complain of nervousness, bowel changes, and a fast heart beat.
Hypothyroidism (undersecretion of thyroid hormones) causes a slow metabolic rate with resultant weight gain, goiter, apathy, and bradycardia. These people may complain of feeling tired all the time and sluggishness.
Both conditions are readily treatable with proper diagnosis. They are also genetically passed from generation to generation.