Ruchi Mathur, MD, FRCP(C) is an Attending Physician with the Division of Endocrinology, Diabetes and Metabolism and Associate Director of Clinical Research, Recruitment and Phenotyping with the Center for Androgen Related Disorders, Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Many of my patients ask questions or make comments about iodine use in thyroid disease. Examples are: " Should I increase the iodine in my diet if I'm hypothyroid?" "My mother had hyperthyroidism, and they told her it was because of a lack of iodine." " My sister has thyroid disease, and to avoid getting it, I'm taking Kelp tablets." "Can I eat sushi if I take Synthroid?"
Although these questions and comments are relevant, this subject is peppered with "old wives tales" and folklore. In the first part of this discussion, I'd like to focus on the role iodine in relation to the thyroid gland and its function.... a bit of physiology for the beginner. Later, I will discuss how an excess or deficiency of iodine can contribute to diseases of the thyroid gland.
Hypothyroidism
is a condition characterized by abnormally low thyroid
hormone production. There are many disorders that result in
hypothyroidism. These disorders may directly or indirectly involve the thyroid
gland. Because thyroid hormone affects growth, development, and many cellular processes, inadequate thyroid hormone has widespread consequences for the body.
This article will focus specifically on hypothyroidism in adults.
What are thyroid hormones?
Thyroid hormones are produced by the thyroid gland. This gland is located in the lower
part of the neck, below the Adam's apple. The gland wraps around the windpipe
(trachea) and has a shape that is similar to a butterfly - formed by two wings (lobes) and
attached by a middle part (isthmus).
The thyroid gland uses iodine (mostly available from the
diet in foods such as seafood, bread, and salt) to produce thyroid hormones. The two most
important thyroid hormones are thyroxine (T4) and triiodothyronine (T3), which account
for 99% and 1% of thyroid hormones present in the blood respectively.
However, the hormone with the most biological activity is T3. Once released from
the thyroid gland into the blood, a large amount of T4 is converted into T3 -
the active hormone that affects the metabolism of cells.
Thyroid hormone regulation- the chain of command
The thyroid itself is regulated by another gland that is located in
the brain, called the pituitary. In turn, the pituitary is regulated in part by the thyroid
(via a "feedback" effect of thyroid hormone on the pituitary gland) and by another gland called
the hypothalamus.
The hypothalamus releases a hormone called thyrotropin releasing hormone (TRH), which sends a
signal to the pituitary to release thyroid stimulating hormone (TSH). In turn, TSH sends a
signal to the thyroid to release thyroid hormones. If a disruption occurs at any of these
levels, a defect in thyroid hormone production may result in a deficiency of thyroid hormone
(hypothyroidism).
Hypothalamus - TRH
Pituitary- TSH
Thyroid- T4 and T3
The rate of thyroid hormone production is controlled by the pituitary gland. If there is an
insufficient amount of thyroid hormone circulating in the body to allow for normal functioning,
the release of TSH is increased by the pituitary gland in an attempt to stimulate more thyroid
hormone production. In contrast, when there is an excessive amount of circulating thyroid
hormone, TSH levels fall as the pituitary attempts to decrease the production of thyroid hormone.
In persons with hypothyroidism, there is a persistent low level of circulating thyroid
hormones.
Dizziness is a symptom that is often applies to a variety of sensations including lightheadedness and vertigo. Causes of dizziness include low blood pressure, heart problems, anemia, dehydration, and more. Treatment of dizziness depends on the cause.
Hyperthyroidism is an excess of thyroid hormone resulting from an overactive thyroid gland. Symptoms can include increased heart rate, weight
loss, depression, and cognitive slowing. Treatment is by medication, the use of
radioactive iodine, thyroid surgery, or reducing the dose of thyroid hormone.
There are four major types of thyroid cancer: papillary, follicular, medullary, and anaplastic thyroid cancer. Tumors on the thyroid are referred to as thyroid nodules. Symptoms of thyroid cancer include swollen lymph nodes, pain in the throat, difficulty swallowing, hoarseness, and a lump near the Adam's apple. Treatment usually involves chemotherapy, surgery, radioactive iodine, hormone treatment or external radiation and depends upon the type of thyroid cancer, the patient's age, the tumor size, and whether the cancer has metastasized.
Stress occurs when forces from the outside world impinge on the individual. Stress is a normal part of life. However, over-stress, can be harmful. There is now speculation, as well as some evidence, that points to the abnormal stress responses as being involved in causing various diseases or conditions.
Raynaud's phenomenon is characterized by a pale-blue-red sequence of color changes of the digits, most commonly after exposure to cold. Occurring as a result of spasm of blood vessels, the cause is unknown. Symptoms of Raynaud's phenomenon depend on the severity, frequency, and duration of the blood vessel spasm. Treatments include protection of the digits, medications, and avoiding emotional stresses, smoking, cold temperature, and tools that vibrate the hands.
Restless leg syndrome (RLS or restless legs syndrome) is a common cause for painful legs that typically eases with motion, and becomes worse and more noticeable at rest. This characteristic nighttime worsening can frequently lead to insomnia. Treatment of the symptoms of restless leg syndrome is generally with medication as well as treating any underlying condition causing restless leg syndrome.
Hashimoto's thyroiditis is the most common cause of hypothyroidism in the US. This conditions is caused by inflammation of the thyroid gland. Symptoms may include: fatigue, weight gain, cold intolerance, excessive sleepiness, dry or coarse hair, difficulty swallowing, a lump in the front of the throat, and many more. Treatment is usually hypothyroid medication.
Carpal tunnel syndrome is a condition in which irritation of the wrist's median nerve causes tingling and numbness of the thumb, index, and the middle fingers. This condition is known as tarsal tunnel syndrome in the ankles and feet. Treatment of carpal tunnel syndrome depends on the severity of the symptoms and the nature of any disease that might be causing the symptoms.
Thyroid nodules are the most common endocrine problem in the United States. The term "thyroid nodule" refers to any abnormal growth that forms a lump in the thyroid gland. The vast majority of thyroid nodules are benign.
Hyponatremia is a condition where the level of sodium in the blood is low. Causes of hyponatremia can occur from excess fluid in the body, or a loss of sodium in body fluid. Some of the symptoms of hyponatremia include headache, muscle cramps or spasm, seizures, weakness and confusion. Treatment of hyponatremia depends on the cause.
There are many types of thyroid disease. Some occur due to the function of the thyroid itself such as hypothyroidism, hyperthyroidism, Hashimoto's thyroiditis, etc. Some causes of thyroid disease occur due to problems with the structure of the thyroid gland such as goiters, thyroid nodules, and thyroid cancer. Treatment of thyroid disease depends on the cause of the disease.
Rhabdomyolysis is a rapid deterioration and destruction of skeletal muscle. Some of the causes of rhabdomyolysis include severe burns, muscle trauma, coma, seizures, electrolyte imbalance, medications (statins), viruses, bacteria. Treatment of rhabdomyolysis depends on the cause.
Obesity is the state of being well above one's normal weight. A person has traditionally been
considered to be obese if they are more than 20 percent over their ideal weight.
That ideal weight must take into account the person's height, age, sex, and
build.
Pleural effusion is an excess fluid between the two membranes that envelop the lungs. There are two classifications of causes of pleural effusion; transudate and exudate. The treatment of pleural effusion depends on the cause.
Hypothyroidism during pregnancy can be treated with synthetic thyroid hormones to maintain the proper thyroid hormone balance. Hypothyroidism symptoms include fatigue, weight gain, lethargy, and constipation. Treatment of hypothyroidism in pregnant women is important, because inadequate levels of thyroid hormones may affect the fetus, and child during growth and development.
Hypothermia is having a body core temperature of less than 35 C or 95 F. Most causes of hypothermia are preventable. Risk factors for hypothermia include age, mental status, medical conditions, and medications. Symptoms of hypothermia generally depend upon the severity of the condition. Treatment depends upon the severity of hypothermia. If not treated early, hypothermia can lead to cardiac arrest, coma, or death.
Amenorrhea is a condition in which there is an absense of menstrual periods in a woman. There are two types of amenorrhea, 1) primary and 2) secondary. Treatment of amenorrhea depends on the type (primary or secondary). In prmiray, surgery may be an option and in secondary amenorrhea medication or lifestyle changes may be treatment options.
Fatigue can be described in various ways. Sometimes fatigue is described as feeling a lack of energy and motivation (both mental and physical). The causes of fatigue are generally related to a variety of conditions or diseases for example, anemia, mono, medications, sleep problems, cancer, anxiety, heart disease, drug abuse, and more. Treatment of fatigue is generally directed toward the condition or disease that is causing the fatigue.
Dry skin (xeroderma) may be caused by external factors, like cold temperatures, low humidity, harsh soaps, and certain medications, or internal factors, such as thyroid disease, diabetes, psoriasis, or Sjogren's syndrome. Symptoms and signs of dry skin include itching and red, cracked or flaky skin. The main treatment for dry skin is frequent, daily lubrication of the skin.
Myxedema coma is the loss of brain function due to severe longstanding low levels of thyroid hormone in the blood. Myxedema coma is a life-threatening complication of hypothyroidism. Examples of triggers of myxedema coma include medications, infections stroke, trauma and more. Some of the ymptoms of myxedema coma include: hypothermia, seizures, coma, difficulty breathing and more. Treatment of myxedema coma depend on the severity of the condition.
Premature ovarian failure (POS) is the cessation of normal functioning of the ovaries in women under the age of 40. Premature ovarian failure may be caused by follicle depletion or dysfunction. The most common symptom of premature ovarian failure are irregular periods. There is no "treatment" that will restore the ovarian function, but there are treatments that my relieve symptoms.
Millions of women suffer from urinary incontinence (UI). UI occurs twice as often in women as in men. There are many types of urinary incontinence: stress incontinence, urge incontinence, overactive bladder, functional incontinence, overflow incontinence, transient incontinence, and mixed incontinence.
Thyroiditis is the inflammation of the thyroid gland. The inflamed thyroid gland can release an excess of thyroid hormones into the blood stream, resulting in a temporary hyperthyroid state. Some forms of thyroiditis can be diagnosed based on tenderness and enlargement of the thyroid gland. A thyroid scan sometimes is used in making the diagnosis. Thyroiditis can also be diagnosed with a biopsy of the thyroid gland.
Cholesterol occurs naturally in the body. High blood cholesterol levels increase a person's risk of developing heart disease, heart attacks, strokes, TIAs, and more. In addition to medication (fibrates, statins, bile acid sequestrants, and niacin), lifestyle changes can be made to lower blood cholesterol levels
Pendred syndrome, a genetic disorder that causes hearing loss. Generally, the hearing loss is affected in early childhood. Pendred syndrome also affects other parts fo the body (for example, the thyroid gland). Treatment is generally cochlear ear implants.
Hashimoto's thyroiditis is the most common cause of hypothyroidism in the
United States. It is named after the first doctor who described this condition,
Dr. Hakaru Hashimoto, in 1912.
What causes Hashimoto's thyroiditis?
Hashimoto's thyroiditis is a condition caused by inflammation of the
thyroid gland. It is an
autoimmune disease, which means that the body inappropriately attacks the thyroid
gland--as if it was foreign tissue. The underlying cause of the autoimmune
process still is unknown. Hashimoto's thyroiditis tends to occur in families, and is
associated with a clustering of other autoimmune conditions such as Type 1
diabetes, and celiac disease. Hashimoto's
thyroiditis is 5-10 times more common in women
than in men and most often starts in adulthood. Blood drawn from patients with
Hashimoto's throiditis reveals an increased number of antibodies to the enzyme, thyroid
pero...
Many of my patients ask questions or make comments about iodine use in thyroid disease. Examples are: " Should I increase the 
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