MedicineNet.com
About Us | Privacy Policy | Site Map
February 9, 2010
MedicineNet home Picture Slideshows Diseases and conditions Symptoms and signs Procedures and tests Medications Picture Image Collection MedTerms medical dictionary Pet Health
Font Size
A
A
A


Hypothyroidism

Medical Author: Ruchi Mathur, MD, FRCP(C)
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
Doctor to Patient

Thyroid, Iodine, & Diet: What You Should Know

Medical Author: Ruchi Mathur, MD
Medical Editor: William C. Shiel, Jr, MD, FACP, FACR

Diet and HypothyroidismMany 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.


Doctor to Patient

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 Gland illustration - Hypothyroidism

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
down arrow
Pituitary- TSH

down arrow
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.

Illustration of the Pituitary Gland



Next: What causes hypothyroidism? »

Hypothyroidism - Symptoms Experienced

The MedicineNet physician editors ask:

For hypothyroidism, what were the symptoms and signs you experienced?

Comment submissions for this question have ended. Patient Discussions FAQs
See 30 Viewer Comments

View Comments


Printer-Friendly Format  |  Email to a Friend


Suggested Reading by Our Doctors
MedicineNet Doctors
  • 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


Women's Health

Find out what women really need.


Are you Depressed? Take the Quiz

Your Guide to Symptoms & Signs: Pinpoint Your Pain



Hypothyroidism

Introduction to thyroid disease

When I was asked to write an article on "thyroid disease", I took a very deep breath. The task seemed daunting. As any Endocrinologist (hormone specialist) knows, there are many subtopics within this giant topic, and an article like this could go on for a hundred pages! So, once I caught my breath, I decided to simply design this article to present a "rough guide" to the thyroid. This article will be an outline or introduction to many conditions that involve the thyroid gland. As you read through this, you will find a number of links that will take you to more in-depth articles dealing with the specific topic in question.

Thyroid 101: What is the thyroid and what does it do?

The thyroid is a butterfly-shaped gland located in the front of the neck just below the Adams apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly ...

Read the Thyroid Disease article »









  • More Resources
    on WebMD
  • More Resources
    on eMedicineHealth
  • More Resources
    on RxList

More Hypothyroidism Resources on WebMD

Hypothyroidism Exams and Tests

A thorough medical history and physical exam are the first steps in diagnosing hypothyroidism or mild (subclinical) hypothyroidism. If the results lead your doctor to suspect you have hypothyroidism or subclinical hypothyroidism, you will have tests to confirm the diagnosis.

Blood tests are always used to confirm a diagnosis of hypothyroidism or mild hypothyroidism. The tests used most often are:

Thyroid-stimulating hormone (TSH) assay.

Thyroxine (T4) measurement.

If the above tests are not normal, the antithyroid antibody test may determine whether you have the autoimmune disease Hashimoto's thyroiditis, in which the body's defense system attacks the thyroid gland.

Learn more about exams and test for hypothyroidism »

More Hypothyroidism Resources on eMedicineHealth

Thyroid FAQs

The thyroid is an organ that is considered part of the endocrine, or hormone system. It is located in the neck below the Adam's apple. The thyroid's main purpose is to produce thyroid hormones. These hormones then travel through the body in the bloodstream to all the other tissues and organs to help control metabolism.

Learn more about the thyroid »

More Hypothyroidism Resources on RxList

Cytomel (liothyronine sodium)

This drug may be one drug prescribed for or symptoms of Hypothyroidism.

Thyroid hormone drugs are indicated:

As replacement or supplemental therapy in patients with hypothyroidism of any etiology, except transient hypothyrodism during the recovery phase of subacute thyroiditis. This category includes cretinism, myxedema and ordinary hypothyroidism in patients of any age (pediatric patients, adults, the elderly) or state (including pregnancy); primary hypothyroidism resulting from functional deficiency, primary atrophy, partial or total absence of thyroid gland, or the effects of surgery, radiation, or drugs, with or without the presence of goiter and secondary (pituitary) or tertiary (hypothalamic) hypothyroidism (see WARNINGS).

As pituitary thyroid-stimulating hormone (TSH) suppressants, in the treatment or prevention of various types of euthyroid goiters, including thyroid nodules subacute or chronic lymphocytic thyroiditis (Hashimoto's) and multinodular goiter.

Learn more about the drug Cytomel »



Health categories:

Slideshows | Diseases & Conditions | Symptoms & Signs | Procedures & Tests | Medications | Image Collection | Medical Dictionary | Pet Health

Popular health centers:

Allergies | Arthritis | Blood Pressure | Cancer | Chronic Pain | Cold & Flu | Diabetes | Digestion | Eyesight | Health & Living | Healthy Kids

Hearing & Ear | Heart | Infectious Disease | Men's Health | Mental Health | News & Views | Pregnancy | Sexual Health | Skin | Women's Health | More...

MedicineNet.com:

About Us | Newsletters | RSS Feeds | Privacy Policy | Site Map | WebMD® | Medscape® | eMedicine® | eMedicineHealth® | RxList®

This website is certified by Health On the Net Foundation. Click to verify. This site complies to the HONcode standard for trustworthy health information:
verify here.

©1996-2010 MedicineNet, Inc. All rights reserved. Notices and Legal Disclaimer.
MedicineNet does not provide medical advice, diagnosis or treatment. See additional information.