What is the thyroid?
Your thyroid gland is located in the front of your neck, just below your voice box. The thyroid produces two forms of thyroid hormone, both of which are derived from the amino acid tyrosine and several atoms of iodine. Thyroid hormones control your body’s metabolism, regulating everything from body temperature and heart rate to glucose consumption and even blood lipid levels.
Too much thyroid hormone (hyperthyroidism) results in an excessively high metabolic rate. People with this condition have rapid heart rates and often palpitations, excessive sweating, and may feel much warmer than other people do, even in a cool room. In extreme cases they may lose weight and experience muscle weakness.
Too little thyroid hormone (hypothyroidism) results in just the opposite set of symptoms: a slower than normal heart rate,29 a chronic feeling of being cold, constipation, unexplained weight gain, dry skin, hair loss or coarse dry hair, weakness, muscle aches, depression, and fatigue. In extreme cases, people with low thyroid function experience cognitive decline, and babies born to mothers with inadequate iodine levels are at high risk for a unique form of mental retardation known as cretinism. Cognitive impairment caused by low thyroid function is reversible with iodine or thyroid hormone supplementation.
Both over- and under-production of thyroid hormone are associated with the thyroid gland swelling known as goiter. In hyperthyroidism, the goiter is the result of inflammation of the gland as it is under attack by an overactive immune system.
In hypothyroidism, the goiter develops as the thyroid attempts to make more thyroid hormone in the absence of sufficient dietary iodine.
Iodine deficiency is the most common cause of goiter, and since it causes hypothyroidism, is also the most common endocrine (glandular) problem in the world. Iodine deficiency is most prevalent in people who live far inland, away from the oceans that provide our best source of iodine. Those areas are commonly referred to as “goiter belts,” because of the high rates of impaired thyroid function.
Iodine deficiency disorders can produce symptoms of low thyroid function (hypothyroidism) even without abnormalities in measured thyroid hormone levels. Recent evidence suggests, for example, that iodine deficiency is linked to obesity, cognitive impairment, psychiatric disorders, fibromyalgia, and a variety of cancers.
Paradoxically, another major consequence of mild-to-moderate iodine deficiency in older adults is hyperthyroidism (excessive thyroid function), especially in women. This is the result of rapidly growing thyroid gland nodules that over-produce thyroid hormone; it can trigger cardiac arrhythmias, osteoporosis, and muscle wasting.
Among those negative consequences is the impact of iodine deficiency on breast health. Compelling data are emerging that link iodine deficiency to breast cancers and high rates of fibrocystic breast disease, two of the greatest concerns of older women in the US. It’s worth exploring those data here; including evidence that iodine supplementation can promote healthy breast tissue.
Fortunately, all iodine deficiency disorders and related health dangers can be prevented by adequate intake of iodine.