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What organs are affected by hypothyroidism?


In medical terms, the suffix -itis means inflammation; thyroiditis is inflammation of the thyroid gland which may be associated with an underactive thyroid gland or hypothyroidism. In some cases, people have an overactive thyroid gland or hyperthyroidism prior to experiencing hypothyroidism.

There are several different kinds of thyroiditis. Although each different type of thyroiditis may cause different symptoms, many times they can be quite similar.

In the case of thyroiditis, the thyroid gland is damaged by an inflammatory process. When thyroid cells are attacked by inflammation, they stop functioning. Without thyroid cells, the thyroid is no longer able to produce enough thyroid hormone to maintain the body’s normal metabolism. Hypothyroidism, or an underactive thyroid gland, results.

Hashimoto’s Thyroiditis

Hashimoto’s thyroiditis, also called chronic lymphocytic thyroiditis, is the most common form of thyroiditis. This is an autoimmune form of thyroiditis that may run in families. Families that suffer from non-thyroid autoimmune disease such as Type 1 diabetes or rheumatoid arthritis may also be at risk for the development of Hashimoto’s thyroiditis.

Most people with Hashimoto’s thyroiditis don’t even realize they have any thyroid disease because the symptoms are initially very mild. Most often the thyroid enlarges slightly so that it appears bulky and larger. This enlargement is due to the inflammatory cells which destroy the thyroid, resulting in long term scarring. When the cells are damaged they cease thyroid hormone production, resulting in hypothyroidism. Again the symptoms are usually mild, e.g. fatigue, difficulty concentrating and weight gain. But they can progress and become quite severe, affecting every organ system in the body.

Occasionally, people with Hashimoto’s’ thyroiditis develop an overactive thyroid (hyperthyroidism) rather than the usual hypothyroidism. Hyperthyroidism in this case develops when thyroid hormone gets released into the blood stream as thyroid cells are destroyed. This hyperthyroid period is generally short, and is followed by a period of time when the thyroid functions properly. Sometimes, however, this period of normal thyroid function is short-lived and as scarring sets in, hypothyroidism results.

The diagnosis of Hashimoto’s thyroiditis is made using two blood tests: first, a routine thyroid function test to confirm an underactive thyroid gland; and second, thyroid antibody tests (anti-microsomal or anti-thyroglobulin antibodies), which pinpoint Hashimoto’s thyroiditis as the cause of the hypothyroidism. Anti-microsomal and anti-thyroglobulin antibodies are immune components that the body produces to attack specific portions of the thyroid cells. The anti-microsomal antibody test is much more sensitive than the anti-thyroglobulin test, therefore some doctors use only the former blood test. These thyroid autoantibody blood levels are high in about 95% of patients with Hashimoto’s thyroiditis.

Although the thyroid gland enlarges with Hashimoto’s’ thyroiditis and sometimes even has exaggerated contours called bossilations, Hashimoto’s thyroiditis does not form discrete nodules or lumps in the thyroid. If you have Hashimoto’s thyroiditis and a thyroid lump, it must be examined completely to insure that this nodule does not represent a cancer. This examination is usually done by needle biopsy to prove whether or not the thyroid lump is benign or malignant. Although you are unlikely to develop thyroid cancer and Hashimoto’s thyroiditis together, you are at increased risk for a special type of thyroid cancer called a lymphoma which can be treated and cured if discovered early. Therefore, no thyroid nodule should be ignored.

Painful Thyroiditis

Subacute granulomatous thyroiditis, or painful thyroiditis, is a form of thyroid disease that occurs equally in both men and women. It usually starts out as a harmless viral illness such as the flu or a cold which invades the thyroid gland causing thyroiditis. This type of inflammation is quite painful and you may find that the front of your throat is sore to the touch. Often this pain extends to the jaw or ear and can be confused with a whole host of other diseases including temporomandibular joint problems (commonly referred to as TMJ), ear infections or even Strep throat. Sometimes only one lobe of the thyroid is affected causing pain and swelling on just one side of the neck instead of both.

Gradually the thyroid recovers and stops spilling thyroid hormone into the blood stream. The thyroid gland begins to shrink and becomes less tender. The thyroid cells recover and are usually able to produce normal amounts of thyroid hormone. Occasionally, however, the thyroid has been destroyed and can never produce normal quantities of thyroid hormone. In this case, permanent hypothyroidism results and thyroid hormone replacement medication is necessary.

The diagnosis of painful thyroiditis is made by routine thyroid function blood tests which may initially show an overactive thyroid because of the sudden release of a surplus of thyroid hormone into the blood stream as the thyroid is attacked by the virus. A radioactive iodine scan will show almost no concentration of the radioiodine by the thyroid cells because these cells are temporarily injured during the inflammatory process. In the situation where only one side of the thyroid gland is enlarged, it can mimic the symptoms of thyroid cancer, therefore a thorough history, including recent viral infections, must be considered. In addition, if the thyroid only shrinks on one side after the infection, it also may be misdiagnosed as a thyroid cancer, therefore it is important that you inform your doctor about the painful initial swelling.

Sometimes medications like aspirin or ibuprofen can be taken under the direction of a physician to help decrease the amount of pain. If the thyroid cells recover, no additional medication is needed. However, if the damage is permanent, replacement doses of thyroid hormone medication must be taken for the rest of your life to treat the hypothyroidism. There is no way to tell who will eventually end up with an underactive thyroid gland. Therefore it is very important to have routine visits with your doctor, to make sure that your thyroid gland is still functioning normally. This information is obtained by routine thyroid function blood tests.

Painless Thyroiditis

Painless thyroiditis, also called subacute lymphocytic thyroiditis, is the type of thyroiditis that may occur in women after they give birth. Initially the overactive or hyperthyroid phase is more common with the destruction of thyroid tissue caused by inflammation. This results in excess thyroid hormone being released into the blood. As a result patients may have a slight enlargement of the thyroid gland and may notice increased anxiety, restlessness, insomnia, weight loss, and difficulty concentrating.

This overactive phase is diagnosed by blood tests to measure the abnormally increased levels of thyroid hormone in the bloodstream and also sometimes the abnormal antibodies, anti-microsomal and antithyroglobulin antibodies During this hyperthyroid phase, treatment is usually not recommended because this phase usually lasts for a short period of time, about 2 to 4 months. However, if the symptoms are extreme, beta blockers may be used to slow the heart rate and decrease nervousness.

The second phase of postpartum thyroiditis is an underactive or hypothyroid period and usually occurs 3 to 8 months postpartum. This phase can be characterized by a slight enlargement of the thyroid gland and symptoms of weight gain, fatigue, lack of energy and often depression. In fact, some cases of postpartum depression have actually been linked to postpartum thyroid disease and are readily treatable. Permanent hypothyroidism may develop especially if you have high antibody levels or a severe hypothyroid phase. Treatment for this hypothyroid phase is with thyroid hormone medication for about six months. After this time, the medication is stopped to determine whether or not the thyroid has recovered its normal function. If so, the medication may be stopped permanently, otherwise the medication must be resumed because of permanent injury to the thyroid gland.

Reidel’s Thyroiditis

Riedel’s invasive fibrous thyroiditis is a very rare form of thyroiditis in which the inflammation of the thyroid gland causes it to merge with surrounding structures such as muscle and trachea (windpipe). In fact, many physicians think that this disease is not a form of thyroiditis at all, but rather a rare form of low-grade tumor that happens to involve the fascia (or envelope) of tissue that surrounds the thyroid gland.

The thyroid gland itself becomes quite hard, like a rock and it may be very difficult to tell if this rock-hard thyroid is a result of inflammation or cancer. Blood tests for thyroid function are usually normal except in the extreme cases where the inflammation is so invasive that the thyroid can no longer function properly. In this situation, you may become hypothyroid. A biopsy is necessary in order to distinguish this benign disease from cancer. However, since the thyroid gland in this illness is so hard, a fine needle aspiration biopsy may not be possible. Instead, a biopsy done in the operating room may be necessary.

In the most severe forms of this disease, the thyroid gland becomes so tight and solid that it may squeeze the trachea or breathing tube. In this instance, an operation may be necessary to remove the middle portion of the thyroid and remove this constricting ring. A complete removal of the thyroid gland can not be performed because the thyroid blends with normal muscles and other tissues, making more extensive surgery quite dangerous. Once this little middle portion of the thyroid is removed, the windpipe is no longer constricted and breathing is facilitated.

Acute Suppurative Thyroiditis

Acute suppurative thyroiditis is a rare form of thyroiditis caused by a bacterial infection that causes pus to collect and form an abscess within the thyroid gland. The bacterial infection may be carried in the bloodstream from anywhere in the body or it may come from the throat itself. Because antibiotics are now routinely used, this form of thyroiditis has become very rare since bacterial infections are usually treated before they spread to the thyroid gland. In the few instances where it still occurs, antibiotics and surgery to drain the pus can result in complete cure.

Next Steps

If you are dealing with a thyroid issue, our team at the Columbia Thyroid Center is here to help. Call (212) 305-0444 or request an appointment online.

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Hyperthyroidism in Cats

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Hyperthyroidism is a common disease in cats, and mostly afflicts cats middle-aged and older.

Also called thyrotoxicosis, hyperthyroidism is caused by an increase in production of thyroid hormones (known as T3 and T4) from an enlarged thyroid gland in a cat’s neck. In most cases, enlargement of thyroid glands is caused by a non-cancerous tumor called an adenoma. Some rare cases of hyperthyroid disease are caused by malignant tumors known as thyroid adenocarcinomas. Although the cause of feline hyperthyroidism is not known, possible contributing factors include deficiencies or excesses of certain compounds in the diet and chronic exposure to thyroid-disrupting chemicals in food or the environment.

Thyroid hormones affect nearly all of the organs in the body; therefore, thyroid disease often causes secondary problems.

Clinical Signs
Cats afflicted with hyperthyroidism usually develop a variety of signs that may be subtle at first but that become more severe as the disease progresses. The most common clinical signs of hyperthyroidism are weight loss, increased appetite, and increased thirst and urination. Hyperthyroidism may also cause vomiting, diarrhea, and hyperactivity. The coat of affected cats may appear unkempt, matted, or greasy (see Figure 1).

A veterinarian who suspects a cat has a thyroid problem will conduct a physical examination and palpate the cat’s neck area to check for an enlarged thyroid gland (see Figure 2). The cat’s heart rate and blood pressure may also be checked. If thyroid disease is a possibility, your veterinarian will likely order a blood chemistry panel and an analysis of thyroid hormone levels. Most cats with hyperthyroidism have elevated levels of the thyroid hormone T4 in their bloodstream, but a small percentage of cats with hyperthyroidism have T4 levels within the normal range. If your cat does not have elevated T4 levels but your veterinarian still suspects your cat has hyperthyroidism, additional tests may be recommended. Since hyperthyroidism can predispose a cat to other conditions, it is important to evaluate general health, with particular focus on the heart and kidneys. A blood chemistry panel and urinalysis will provide information about other organs and provide your veterinarian with an overall picture of your cat’s health.

There are four treatment options for feline hyperthyroidism: medication, radioactive iodine therapy, surgery, and dietary therapy. Each treatment option has its advantages and disadvantages. The treatment a cat receives for hyperthyroidism will depend on specific circumstances, including the patient’s overall health status, the owner’s ability and willingness to medicate the cat regularly, and financial considerations.

Anti-thyroid drugs act by reducing the production and release of thyroid hormone from the thyroid gland. These medications do not provide a cure for the disease, but they do allow either short-term or long-term control of hyperthyroidism. The advantages of medication are that the drugs are readily available and relatively inexpensive. Some cats may experience side effects from medication, however, including vomiting, anorexia, fever, anemia, and lethargy. Lifelong treatment, usually involving twice-daily oral dosage, will be required, and for some owners and cats, this dosage schedule may be difficult to maintain. Antithyroid medications are also available in a gel that can be applied to the skin. The effectiveness of this transdermal gel is acceptable in most cases. Regardless of the medication, blood tests should be conducted periodically during treatment to evaluate whether the therapy is effective and to monitor kidney function and for potential side effects.

Radioactive Iodine Therapy
When available, radioactive iodine therapy is the treatment of choice for cats with hyperthyroidism. During treatment, radioactive iodine is administered as an injection and is quickly absorbed into the bloodstream. The iodine, which is required for the production of both T3 and T4, is taken up by the thyroid gland and the emitted radiation destroys the abnormal thyroid tissue without damaging the surrounding tissues or the parathyroid glands. The majority of cats treated with radioactive iodine have normal hormone levels within one to two weeks of treatment.

The advantages of radioactive iodine therapy are that the procedure most often cures hyperthyroidism, has no serious side effects, and does not require anesthesia. It does, however, involve the handling and injection of a radioactive substance that is only permitted at facilities specially licensed to use radioisotopes. The radioactivity carries no significant risk for the cat, but precautionary protective measures are required for people who come into close contact with the cat. A treated cat has to remain hospitalized until its radiation level has fallen to within acceptable limits. Usually this means that the cat will need to be hospitalized for between three and five days after treatment. Because of strict treatment guidelines, most facilities will not allow visitors during this quarantine period.

Radioactive iodine therapy is curative within three months of therapy in approximately 95 percent of all hyperthyroid cases. In cases where radioactive iodine therapy is not successful, the treatment can be repeated. Rarely, a permanent reduction in thyroid-hormone levels called hypothyroidism occurs after radioactive iodine treatment. If this is accompanied by clinical signs such as lethargy, obesity, and poor hair coat, then thyroid hormone supplementation may be required.

Removal of the thyroid glands, called surgical thyroidectomy, is a relatively straightforward surgical procedure that has a good success rate. The advantage of surgery is that it is likely to produce a long-term or permanent cure in most cats, and therefore eliminates the need for long-term medication.

This surgery requires general anesthesia, however, and there might be added risks if older cats have heart, kidney, or other problems that could cause complications. One major risk associated with surgical thyroidectomy is inadvertent damage to the parathyroid glands, which lie close to or within the thyroid gland and are crucial in maintaining stable blood calcium levels. Medication and radioactive iodine therapy are just as effective at treating hyperthyroidism in cats as surgery and are less invasive, so surgical treatment is rarely chosen for treating this condition.

Dietary Therapy
Certain studies suggest that in some hyperthyroid cats, limiting the amount of iodine in the diet may be a viable option for treating this disease. This may be particularly useful in cats with medical conditions that make other treatment options impossible. Dietary restriction of iodine is, however, somewhat controversial because of concerns about the effects of long-term iodine restriction on overall health and the possibility that such a diet may actually backfire and worsen hyperthyroidism. Research into this potential treatment option is ongoing. Discuss these issues with your veterinarian when considering dietary iodine restriction as a treatment for hyperthyroidism in cats.

Secondary Problems
Because of the important role the thyroid gland plays in the body, some cats with hyperthyroidism develop secondary problems, including heart disease and high blood pressure.

Elevated thyroid hormones stimulate an increased heart rate and a stronger contraction of the heart muscle, and can cause thickening of the left ventricle of the heart over time. If left untreated and unmanaged, these changes may eventually compromise the normal function of the heart and can even lead to heart failure. For this reason, some cats with hyperthyroidism may require additional treatment to control secondary heart disease. However, once the underlying hyperthyroidism has been controlled, the cardiac changes will often improve or may even resolve completely.

Hypertension, or high blood pressure, is another potential complication of hyperthyroidism, and can cause additional damage to several organs, including the eyes, kidneys, heart, and brain. If hypertension is diagnosed along with hyperthyroidism, drugs may be needed to control the blood pressure and reduce the risk of damaging other organs. As in the case of heart disease, after the hyperthyroidism has been successfully treated, high blood pressure will often resolve, and permanent treatment for it may not be required.

The prognosis for cats with hyperthyroidism is generally good with appropriate therapy. In some cases, complications involving other organs may worsen this prognosis.

More specific information on what to expect when your cat is treated with radioactive-iodine therapy at Cornell can be found here.

Updated January 2017

Hypothyroidism Secondary

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Hypothyroidism Secondary: Symptoms, Treatment, Diagnosis


What is Hypothyroidism Secondary?

Secondary hypothyroidism involves decreased activity of the thyroid caused by failure of the pituitary gland.

Alternative Names: Pituitary hypothyroidism

Causes, incidence, and risk factors:

The thyroid gland is an important organ of the endocrine system, located in the front of the neck just below the voicebox. The thyroid secretes the hormones thyroxine (T4), triiodothyronine (T3), and calcitonin, which control body metabolism and regulate calcium balance. The secretion of T3 and T4 by the thyroid is controlled by an endocrine feedback system involving the pituitary gland and the hypothalamus (structures in the brain). Lowered levels of these thyroid hormones result in increased levels of pituitary and hypothalamic hormones. The reverse is also true — when levels of the thyroid hormones rise, pituitary and hypothalamic hormones fall back. This helps keep levels appropriately balanced.

Since the thyroid gland is regulated by the pituitary gland and the hypothalamus, thyroid disorders may result not only from defects in the thyroid itself but also from the disruption of the control system in these other organs. Thyroid disorders caused by overproduction of thyroid hormones are called hyperthyroidism, and underproduction of these hormones is known as hypothyroidism.

The cause of secondary hypothyroidism is failure of the pituitary gland to secrete thyroid stimulating hormone (TSH). This is usually caused by a tumor in the region of the pituitary. Rarely the cause is an infiltration of the pituitary by inflammatory cells from the immune system or foreign substances (such as iron in hemochromotosis). Hypothyroidism may cause a variety of symptoms and can affect all body functions. The body’s normal rate of functioning slows, causing mental and physical sluggishness. Symptoms vary from mild to severe. The most severe form is called myxedema, which is a medical emergency and can lead to coma and death.

Risk factors for secondary hypothyroidism include being over 50 years old, being female, and having a history of pituitary or hypothalamic dysfunction.


  • Weakness
  • Fatigue
  • Cold intolerance
  • Constipation
  • Weight gain
  • Depression
  • Joint or muscle pain
  • Brittle fingernails
  • Coarseness, thinning of hair
  • Slow speech
  • Dry, flaky skin
  • Thickening of the skin
  • Puffy face, hands, and feet
  • Decreased hearing
  • Thinning of eyebrows
  • Hoarseness
  • Menstrual disorders

Signs and tests:

A physical exam usually reveals a small thyroid gland. Vital signs (temperature, pulse, rate of breathing, blood pressure) reveal a slow heart rate, low blood pressure, and low temperature. A chest x-ray may reveal an enlarged heart. Laboratory tests to determine thyroid function include:

  • Free T4 test
  • Total T3
  • Serum TSH — Results are generally low in secondary hypothyroidism because the pituitary is damaged. However, normal or even high values may be seen.

Additional laboratory abnormalities may include:

  • Increased cholesterol levels
  • Increased liver enzymes
  • Increased serum prolactin
  • Low serum sodium
  • Low blood glucose
  • A CBC that shows anemia
  • Deficiency or excess of other pituitary hormones
  • Imaging will include an MRI of the pituitary to look for a tumor.


The purpose of treatment is to replace the deficient thyroid hormone. Levothyroxine is the most commonly used medication. The lowest dose effective in normalizing thyroid function is used. Life-long therapy may be necessary. Medication must be continued even when symptoms subside. After replacement therapy has begun, report any symptoms of increased thyroid activity (hyperthyroidism), such as restlessness, rapid weight loss, and sweating.

A high-fiber, low-calorie diet and moderate activity will help relieve constipation and promote weight loss if weight was gained during the time when thyroid activity was low. In individuals with accompanying hypoadrenalism, steroid replacement must be instituted before thyroid replacement is begun. In patients who have hypothyroidism caused by a pituitary tumor, surgery may be required. However, surgery may not cure the hypothyroidism, and thyroid replacement will still be needed.

Myxedema coma is treated by intravenous (IV) thyroid replacement and steroid therapy. Supportive therapy of oxygen, assisted ventilation, fluid replacement, and intensive care nursing may be indicated.

Support Groups:

Expectations (prognosis):

With early treatment, return to the normal state is usual. However, relapses will occur if the medication is not continued. Myxedema coma can result in death.


Myxedema coma, the most severe form of hypothyroidism, is rare. It may be precipitated by an infection, illness, exposure to cold, or certain medications.

Symptoms and signs of myxedema coma include:

  • Unresponsiveness
  • Decreased breathing
  • Low blood pressure
  • Low blood sugar
  • Below-normal temperature

Other complications include:

  • Heart disease
  • Infertility
  • Miscarriage in pregnant women
  • Adrenal crisis, if thyroid replacement is begun prior to steroids in hypoadrenal patients

Calling your health care provider:
Call your health care provider if signs of hypothyroidism are present, or if chest pain or rapid heartbeat occur. Call your provider if restlessness, rapid weight loss, sweating, or other symptoms occur after beginning treatment for this disorder. Call your provider if headache, visual loss, or breast discharge occur.


This condition may not be preventable. Awareness of risk may allow early diagnosis and treatment.

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