The most common causes of hypothyroidism are:
some prescription drugs
Hormonal imbalance. Women have hypothyroidism at least four (4) times as frequently as do men. This is commonly due to female hormonal imbalance in midlife which leads to a condition known as estrogen dominance. As the ovaries age, women produce decreasing amounts of progesterone, the hormone of the last half of the menstrual cycle. Progesterone deficiency is the cause of estrogen dominance. Estrogen dominance causes the liver to produce increasing levels of a protein, which circulates in the blood, called thyroid binding globulin (TBG). Even when the thyroid gland is producing sufficient amounts of hormone, TBG will bind to the thyroid hormones, lowering the free, unbound thyroid hormone available for use. This in turn causes a decrease in the metabolic rate, lowering the body’s overall energy level. Birth controls pills, pregnancy and postmenopausal estrogen supplementation all lead to increased TBG. Commonly, women complain that their metabolism changed after one of their pregnancies or when they began birth control pills or supplemental counterfeit estrogen hormones. The male hormone, testosterone, does not increase TBG. In fact, testosterone stimulates the conversion of the inactive thyroid hormone, T4, to the active thyroid hormone, T3, within the cells. This is why men have fewer problems with low thyroid function than do women.
Autoimmune Thyroiditis, also known as Hashimoto’s Thyroiditis, is another cause of hypothyroidism. In this disease, the patient’s own immune system is dysregulated and produces antibodies to the individual’s thyroid gland and to the thyroid hormones circulating in the blood. This immune system disorder is frequently associated with allergic disorders. Low intracellular thyroid function and allergies travel together like thieves in the night. In my practice we have tested thousands of individuals since 1991 to determine the presence of thyroid antibodies. Approximately 31% of our female allergy patients and 18% of our male allergy patients have Autoimmune Thyroiditis. This is far greater than the 5% of individuals in the general population who have this disorder. Autoimmune Thyroiditis prevents thyroid hormone from being properly assimilated into the cells.
Nutritional deficiencies. Less commonly than the above, hypothyroidism may be caused by nutritional deficiencies. The thyroid gland requires iodine for the normal production of the thyroid hormones. In the past, hypothyroidism occurred commonly in the Midwest and in the Great Lakes regions of the United States and was characterized by an enlarged thyroid gland, known as a goiter. This condition was due to low iodine levels in the soil and in fresh water fish. With the advent of iodized salt the incidence of this problem has been dramatically reduced. Goiter areas still exist in many areas of the world. Clinical hypothyroidism may also be caused by a selenium deficiency. Selenium is a trace mineral that plays a critical role in the conversion of the inactive hormone, T4, to the active intracellular thyroid hormone, T3. The soil in the United States is deficient in Selenium. The thyroid gland may produce insufficient amounts of the thyroid hormone due to a variety of underlying genetic defects. These conditions are very uncommon.
Another rare cause of the hypothyroidism is pituitary gland dysfunction. The pituitary gland is located in the brain and regulates the thyroid gland by secreting thyroid stimulating hormone (TSH). When there is not a sufficient amount of thyroid hormone in the blood, the pituitary gland increases the production of TSH. If the pituitary gland is diseased and unable to secrete TSH, then the thyroid gland will not produce thyroid hormone.
Prescription drugs, such as Dilantin, Lithium, and Beta Blockers, used in the treatment of hypertension and heart disease, blunt the effect of the thyroid hormones in the cells of the body, leading to symptoms of hypothyroidism. As mentioned earlier, the counterfeit hormones and horse estrogens, such as Premarin, Ogen, and Cenestin, and birth control pills, which are also counterfeit hormones, raise the level of thyroid hormone binding globulin and prevent the proper uptake of thyroid hormones by the cells of the body.