Abnormally high thyroid hormone levels, or hyperthyroidism, can cause increased heart rate, anxiety and weight loss. When thyroid hormone levels drop too low the result is fatigue, weight gain and slowed heart rate, a condition known as hypothyroidism.
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Inflammation of the thyroid gland can disrupt normal thyroid hormone levels in numerous ways. Hashimoto’s thyroiditis is an autoimmune disorder, and one of several diseases that causes inflammation of the thyroid. Hereditary factors, gender, radiation exposure and pregnancy all influence a person’s likelihood of getting Hashimoto’s thyroiditis, according to the U.S. Department of Health and Human Services. This disease is the most common cause of hypothyroidism.
Toxic substances and radiation exposure can also inflame the thyroid gland, prompting an abnormal increase in the release of stored of thyroid hormones.
Postpartum thyroiditis typically affects less than 10 percent of women during the year after giving birth, according the Hormone Foundation. It begins with a 2- to 4-month phase during which the thyroid is overactive. The over-stimulation eventually damages the gland, which then produces less hormone, beginning a hypothyroid phase.
Tumors of the pituitary gland can affect thyroid hormone levels. The pituitary gland produces thyroid stimulating hormone, or TSH. Some pituitary tumors cause an increase in the production of thyroid stimulating hormone, while others can cause decreases. Thyroid stimulating hormone in turn prompts the thyroid to produce greater amounts of hormone.
According to Lab Tests Online, dysfunction of the hypothalamus can alter the pituitary gland’s ability to make TSH, which in turn affects thyroid hormone levels. Benign tumors called adenomas can grow in the thyroid and produce excess thyroid hormone even in the absence of the TSH usually released by the pituitary gland. The Hormone Foundation states that 90 percent of thyroid tumors are benign, but cancerous thyroid nodules do exist, and can spread through the body rapidly.
A deficiency or excess of iodine in the diet can affect the function of the thyroid gland. Iodine is essential for the creation of thyroid hormones. In the United States, iodine is added to salt, which has lead to an elimination of iodine deficiency from the realm of major public health problems, but in some other areas of the world, iodine deficiency still causes problems such as goiter and hypothyroidism.
Overexposure to dietary iodine can cause hyperthyroidism. Dr. Daniel Drucker, Professor of Medicine in the Endocrinology Division at the University of Toronto, states that some dietary supplements, cold remedies, prescription drugs and seaweed products contain amounts of iodine that could prompt a hyperthyroid reaction if taken in excess.