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.
The thyroid gland produces hormones that are essential for normal body metabolism.
Blood testing is now commonly available to determine the adequacy of the levels of
thyroid hormones. These blood tests can define whether the thyroid gland's hormone production is normal, overactive, or
underactive.
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 99.9% and 0.1% 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 (thyroid hormone production is below normal), there is a
continuously decreased level of circulating thyroid hormones. In persons with hyperthyroidism (thyroid
hormone production is above normal), there is a continuously elevated level of circulating thyroid hormones.
Hypothyroidism is any state in which thyroid hormone production is below normal. Normally, the
rate of thyroid hormone production is controlled by the brain at the pituitary.
Hypothyroidism is a very common condition and the symptoms of hypothyroidism are
often subtle.
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.
Muscle spasms are involuntary muscle contractions that come on suddenly and are usually quite painful. Dehydration, doing strenuous exercise in a hot environment, prolonged muscle use, and certain diseases of the nervous system may cause muscle spasms. Symptoms and signs of a muscle spasm include an acute onset of pain and a possible bulge seen or felt beneath the skin where the muscle is located. Gently stretching the muscle usually resolves a muscle spasm.
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.
Fibromyalgia, formerly
known as fibrositis, causes chronic pain, stiffness, and
tenderness of muscles, tendons, and joints without detectable inflammation. Fibromyalgia patients have an unusually low pain threshold. Symptoms of fibromyalgia include fatigue, abnormal sleep, mental/emotional disturbances, abdominal pain, migraine and tension headaches, and irritable bladder. Treatment of fibromyalgia involves patient education, medication, exercise, and stress reduction.
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.
Fainting, also referred to as blacking out, syncope, or temporary loss of consciousness has many causes. Often a person will have signs or symptoms prior to the fainting episode. Diagnosis and treatment depends upon the cause of the fainting or syncope episode.
There are many causes of scalp hair loss. This featured article covers the common ones such as patchy hair loss (alopecia areata, trichotillomania, and tinea capitis), telogen effluvium, and androgenetic alopecia (male-pattern baldness, female-pattern baldness).
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.
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.
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.
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.
Graves' disease is an autoimmune disease that affects the thyroid. Some of the symptoms of Graves' disease include hand tremors, rapid heartbeat, trouble sleeping, enlarged thyroid, thinning of the skin or fine brittle hair. Causes of Graves' disease are thought to be multifactorial such as genes, gender, stress, and infection. Treatment for Graves' disease is generally medication.
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.
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.
Thyroid peroxidase (TPO) is an enzyme made in the
thyroid gland that is
important in the production of thyroid hormone. TPO is found in thyroid follicle
cells where it converts the thyroid hormone T4 to T3.
The thyroid gland is located in the lower part of the neck, below the Adam's
apple, wrapped around the trachea (windpipe).
What is the thyroid peroxidase test?
Thyroid peroxidase test is a test that measures the level of an antibody that
is directed against thyroid peroxidase (TPO).
Autoantibodies to thyroid peroxidase (TPOAb) are produced within the body.
The presence of TPOAb in the blood reflects a prior attack on the thyroid tissue
by the body's immune system.
What does a positive thyroid peroxidase test mean?
Most people with chronic thyroiditis (70%-90%) display a positive TPO test.
The test is also positive in lesser n...
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