The cause of hypothyroidism is the result of several factors, including underlying conditions. These include;
Hashimoto's Thyroiditis: This is the most common cause of hypothyroidism and is categorized as an inherited condition.
Hashimoto's results from an underlying autoimmune disease, in which the body's immune system attacks thyroid tissues. This condition usually presents with an enlarged thyroid gland, or goiter, and inhibits the production of thyroid hormones.
Lymphocytic Thyroiditis: Thyroiditis is an inflammation of the thyroid gland. It is thought to be caused by a type of white blood cell known as a lympocyte.
Severe Iodine Deficiency Hypothyroidism: This results from a dietary deficiency of iodine. Severe hypothyroidism resulting from iodine deficiencies are primarily seen in underdeveloped countries.
Hypothyroidism caused by iodine deficiency is so prevalent, in fact, that an estimated 5-15% of the entire population in lesser developed countries (e.g. Chile and India) suffer from this condition.
This condition is extremely rare in the U.S., due to the inclusion of iodine in table salt and bread products.
Pituitary or Hypothalamic disease: Pituitary disease is also referred to as "secondary hypothyroidism." Hypothalamic disease is defined as "tertiary hypothyroidism."
These two conditions result from the inability of either the pituitary gland or hypothalamus to signal the thyroid for hormone production. Even if the thyroid gland itself is normal, a decreased level of circulating T3 or T4 may still occur as a result of these underlying diseases.
Medications: Common medications used to treat hyperthyroidism (over-active thyroid) can actually cause hypothyroidism.
Psychiatric medications, like lithium, may also diminish thyroid hormone production. The administration of other drugs that contain large amounts of iodine can also lead to extremely low levels of thyroid hormone within the blood.
Destruction of the Thyroid: Thyroid destruction typically results from radioactive iodine treatments, radiation therapy, or surgical procedure.
For instance, Grave's disease patients (caused by hyperthyroidism) may receive radioactive iodine therapy, resulting in the destruction or impairment of some, or even all of existing thyroid tissue. Removal of the thyroid gland during surgery is also accompanied with hypothyroidism.
Signs and Symptoms
The signs and symptoms of hypothyroidism often take years to surface, and are solely dependent upon the severity of hormone deficiency.
Moreover, detecting hypothyroidism in infants, children, and teens can prove even more challenging. Classic symptoms include lethargy and extreme fatigue.
However, a greater decline in metabolism usually presents more obvious signs and symptoms of the disease, and may include;
Pale, dry skin
Elevated blood cholesterol levels
Muscle aches and joint stiffness
Heavy menses in females
Increased sensitivity to climate change; particularly the cold
Symptoms of hypothyroidism usually become worse if not accurately diagnosed.
Depression, anxiety, insomnia, and forgetfulness are classic symptoms which can result if not treated correctly. Additionally, advanced hypothyroidism, or myxedema, can be life-threatening.
Although this condition remains extremely rare, persons with intense drowsiness, intolerance to cold, profound lethargy, and periods of unconsciousness warrant immediate medical intervention.
Are You at Risk?
Anyone can develop hypothyroidism. However, women older than 40 years of age have the greatest chance for onset.
Generally, for both sexes, risk factors do increase as our metabolic rates continually decline with age.
Other potential risk factors and at-risk populations include; having a close relative with an autoimmune disease, diabetics, pregnant women, those who are taking anti-thyroid medications or have received radioactive and radiation treatments, as well as persons who have had thyroid surgery (thyroidectomy).