Hypothyroidism
Medical Author: Ruchi Mathur, MD, FRCP(C)
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
 |
Thyroid, Iodine, & Diet: What You Should Know
Medical Author: Ruchi Mathur, MD
Medical Editor: William C. Shiel, Jr, MD, FACP, FACR
 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.
|
 |
What is hypothyroidism?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.
Next: What causes hypothyroidism? »
- levothyroxine sodium, Synthroid, Levoxyl, Levothroid, Unithroid - Learn more about Levothyroxine Sodium (Synthroid, Levoxyl, Levothroid, Unithroid), including a description, generic and brand names, drug class and mechanism, preparations, storage, reasons for prescription, dosing, drug interactions, effect on pregnancy and nursing mothers, and common side effects.
- Thyroid Blood Tests - Read about thyroid blood tests, which are used to diagnose disease of the thyroid such as hyperthyroidism and hyperthyroidism, as well as point to other diseases of the thyroid gland.
- Stress - Read about stress symptoms, signs, causes and treatment. Get information on stress management tips, the effects on the body and stress types (teen, job, PTSD).
Latest Medical News
|
|
 |
From WebMD
Healthy Resources
Featured Centers
Health Solutions From Our Sponsors
Hypothyroidism
Premature Ovarian Failure (POF) »
What is premature ovarian failure (POF)?
Health care providers use the term premature ovarian failure to describe a stop in normal
functioning of the ovaries in a woman under the age of 40. Many women naturally
experience a decline in fertility at age 40; this age may also mark the
beginning of irregularities in their
menstrual cycles that
signal the onset of menopause. For women with
premature ovarian failure, the fertility decline and menstrual
irregularities occur before age 40, sometimes even in the teens. Some health
care providers also use the term primary ovarian insufficiency to describe this
condition.
In the past, health care providers called this condition premature menopause,
but this term is not an accurate description of what happens in a woman with
premature ovarian failure. A woman who has gone through
natural menopause will rarely ever have
another period; a woman with premature ovarian failure is much more likely to have ...
Read the Premature Ovarian Failure (POF) article »
|
Thyroid RSS