Hypothyroidism (Underactive Thyroid)
Hypothyroidism, also referred to as low thyroid or underactive thyroid, is a very common condition that affects millions of North Americans. The most widely prescribed drug in the United States is Synthroid, a synthetic thyroid-hormone replacement used by more than twenty-two million Americans every month.
The thyroid gland, situated at the base of the neck, below the Adam’s apple, secretes hormones that control metabolic activity in every cell of the body. This means the thyroid has an impact on processes as varied as temperature control, weight regulation, heart rate, and energy production. It also affects the balance of other hormones in the body, including the neurotransmitters, which influence mood. In hypothyroidism, the thyroid fails to produce sufficient quantities of its hormones. There are many possible symptoms of hypothyroidism. Common ones include fatigue, weight gain, dry skin, hair loss, constipation, intolerance to cold, and poor memory. See the symptom section below for a complete listing.
About the causes.
The most common cause of hypothyroidism in the United States is Hashimoto’s thyroiditis, an autoimmune disease in which the immune system attacks and destroys thyroid cells. It makes the affected person less able to produce thyroid hormone. In addition, they have an increased risk of thyroid cancer. Hashimoto’s is diagnosed by blood tests that detect elevated thyroid antibodies. The exact cause is unknown, although there seems to be a genetic predisposition. Vitamin D deficiency and gluten sensitivity/allergy increase one’s risk as well. Other possible risk factors include increased intestinal permeability, other hormone imbalances, environmental toxins, other infections, and the effects of stress.
Worldwide, the most common cause of hypothyroidism is iodine deficiency. Iodine is required for the thyroid gland to produce thyroid hormones. Iodine deficiency has become more common in North America in recent years as people avoid iodized salt due to concerns about high blood pressure. Other than in certain seafood and algae products, iodine is not readily available in the diet. In addition, certain chemicals present in the environment and the food supply block iodine from being received by the thyroid gland. These include bromine, fluoride, chloride, and perchlorate. Some research suggests that iodine overload can suppress thyroid function, although this is much less common than iodine deficiency.
Hypothyroidism can also be caused by hormonal changes that accompany pregnancy, certain medications, infectious/inflammatory reactions, and problems with the hypothalamic and pituitary areas of the brain.
Hypothyroidism is more common in women. The balance of estrogen and progesterone can have an indirect influence on the thyroid glands. Most common is estrogen dominance, wherein relatively higher estrogen levels suppress thyroid function. This predisposition can occur throughout a woman’s life. Women on synthetic estrogen therapy are particularly susceptible to decreased thyroid function.
The effects of stress and the balance of stress hormones are also important in thyroid function. Chronic elevation of the stress hormone cortisol suppresses thyroid function. While low levels of DHEA appear to make one more susceptible to hypothyroidism. Toxic metals, such as mercury, lead, arsenic, and others, can also interfere with thyroid activity.