In this UIC Pharmacy blog, you'll find information on your thyroid, its role in the body, and
conditions that may develop when the thyroid fails to function properly.
What is your thyroid
gland?
The thyroid is a small gland that is located at the base of
the neck. This gland has different functions based on one’s age. In adults, it
controls and maintains many necessary metabolic functions, and in children, it
plays an important role in growth and development.
What happens when the
thyroid fails to function properly?
Disruption of thyroid function may lead to development of
thyroid disorders called “hyperthyroidism” and “hypothyroidism.” Information on
these disorders including causes, signs/symptoms, diagnostic medical tests, and
treatment options are described below.
How common are
thyroid disorders?
Thyroid disorders are likely present in around 30 million
Americans. Unfortunately, in approximately half of these cases, the patient may
be unaware that there is a problem with his/her thyroid.
Are there any risk
factors associated with thyroid disorders?
Women tend to be affected more often than men, and
hereditary factors may also contribute to the development of thyroid disorders.
What about thyroid
cancer?
Like with any organ in the body, there is a small risk of
cancer development. Fortunately, thyroid cancer is rare and the majority of cases
can be successfully treated. While not discussed here, more information on
thyroid cancer can be found at the links attached at the end of this post.
Hyperthyroidism
When a person’s thyroid becomes overactive, it can lead to a
state of hyperthyroidism. In patients with this condition, the thyroid
overproduces 2 hormones called T3 and T4. High levels of
these hormones may affect different parts of the body and can lead to many of
the symptoms below.
Signs/Symptoms
·
Nervousness/anxiety
·
Inability to control emotions
·
Irregular heartbeat
·
Rapid heartbeat while at rest
·
Easy fatigability
·
Weight loss despite increased appetite
·
Intolerance to heat
·
Separation of fingernails from nail bed
·
Loss of scalp hair
·
Frequent, loose bowel movements
·
Enlarged thyroid (“goiter”)
·
Trembling of hands
Diagnosis
If your physician suspects that you may have
hyperthyroidism, he/she may have the following tests performed.
T3 or T4 serum concentrations:
As mentioned above, these hormones may be elevated in patients with
hyperthyroidism, especially in severe cases.
Thyroid-stimulating hormone (TSH) serum concentration:
High levels of T3 and T4 inhibit production of this
hormone. Therefore, TSH concentrations may be low in a patient with
hyperthyroidism.
Radioactive Iodine Uptake: Iodine is one of the main
components of the thyroid hormones, T3 and T4. Overproduction
of these hormones can led to depletion of the thyroid’s iodine reserve. To
correct this, the thyroid will increase iodine uptake, which can be measured
following the administration of a small amount of radioactive iodine.
Alternatively, certain cases of hyperthyroidism may be due
to inflammation of the thyroid. In these cases, the radioactive iodine uptake
will actually be decreased.
Causes of
hyperthyroidism
The most common cause of hyperthyroidism is Graves’ Disease,
an autoimmune condition that is more likely to affect women than men. Other causes
include toxic multinodular goiter, toxic adenoma, subacute thyroiditis, and silent
thyroiditis.
In addition, excessive iodine ingestion (present in kelp
tablets and some medications) as well as overmedication with thyroid hormone in
patients being treated for hypothyroidism may occasionally lead to
hyperthyroidism.
Treatment
Thionamides: Propylthiouracil (PTU) and methimazole
(MMI) are members of a class of drugs called thionamides. These medications act
by inhibiting production of thyroid hormones. Dosing can vary based on disease
severity and improvement in symptoms typically begins around 4 to 8 weeks after
initiation of treatment. Length of therapy may also vary, but 12 to 24 months
of treatment is usually necessary to achieve long-term remission.
Treatment with these medications may in some instances lead
to blood abnormalities. Most of the time, these abnormalities are benign and
involve a temporary decrease in the amount of white blood cells. In rare cases,
however, treatment may lead to a more serious condition called agranulocytosis,
usually within the first 3 months of therapy. If the patient taking one of
these medications experiences fever, malaise, or develops a sore throat, they
are encouraged to stop treatment and contact their physician.
Beta-blockers: Medications from this drug class (most
often propranolol) may be added to a patient’s therapy to help control symptoms
such as rapid heartbeat, anxiety, and intolerance to heat. While these
medications can lessen the severity of these symptoms, they have little effect
on the disease itself.
Iodides: Iodide rapidly blocks the release of thyroid
hormones from the thyroid and can lead to symptomatic improvement in a matter
of days. However, because this blockage is temporary, it is not used for
long-term treatment. Its use is instead reserved to prepare patients for thyroid
surgery, to quickly reduce thyroid hormone levels in patients with severely
high levels, and to control hormone release following treatment with
radioactive iodine (discussed below).
Radioactive Iodine: Small amounts of radioactive
iodine are taken by mouth. Because the thyroid normally absorbs iodine, which
is necessary to produce the thyroid hormones, it will also absorb the
radioactive form of iodine. Following absorption, the radioactive iodine will
destroy the portions of overactive thyroid. This treatment is relatively safe
and is often used as the treatment of choice in patients with an overactive
thyroid.
Surgery: Surgical removal of the thyroid is typically
reserved for special situations (e.g. pregnancy with severe uncontrolled
hyperthyroidism) and usually leads to lifelong hypothyroidism.
Hypothyroidism
There are 2 types of hypothyroidism: Primary and Secondary.
Primary hypothyroidism results from improper function of the thyroid itself.
This most often occurs in patients with chronic thyroid inflammation that is
autoimmune in nature (i.e., results from one’s immune system attacking his/her
thyroid). Secondary hypothyroidism is less common and is due
to failure of the pituitary gland, a gland that signals the
thyroid to release thyroid hormones. As one might expect, many of the
signs/symptoms of hypothyroidism are opposite of those associated with
hyperthyroidism.
Signs/Symptoms
·
Cold or dry skin
·
Intolerance to cold
·
Weight gain
·
Constipation
·
Fatigue
·
Depression
·
Loss of ambition
·
Muscle cramps, pain, and stiffness
·
Heavy menstruation
·
Infertility
·
Coarse skin and hair
·
Puffy eyes
·
Carpal tunnel syndrome
·
Numbness or tingling in hands or feet
Diagnosis
If your physician suspects that you may have hypothyroidism,
he/she may have the following tests performed.
T3 or T4 serum concentrations:
These hormones will be low in a patient with hypothyroidism.
TSH serum concentration: Because T3 and T4
normally inhibit production of this hormone, TSH will be elevated when T3
and T4 are low. This is the case in primary hypothyroidism.
Secondary hypothyroidism, however, may lead to normal or elevated levels of
TSH.
Causes of
hypothyroidism
The most common cause of hypothyroidism in the United States
is Hashimoto’s disease, an autoimmune condition that may lead to thyroid
damage. Other causes include radioactive iodine treatment, thyroid removal, congenital
hypothyroidism in newborns, pituitary disease, and central hypothyroidism.
Treatment
Levothyroxine: This synthetic version of the thyroid
hormone, T4, is the treatment of choice for thyroid replacement. In
the body, a portion of levothyroxine will be naturally converted to the other
thyroid hormone, T3, thus it leads to replenishment of both thyroid
hormones in patients with hypothyroidism.
The levothyroxine products produced by different
manufacturers are not interchangeable. Therefore, patients taking levothyroxine
should speak with their physician or pharmacist prior to switching products. In
addition, certain vitamins or dietary supplements may affect absorption of
levothyroxine, so these issues should be discussed with your pharmacist or
physician before beginning to take the medication.
In closing
The troublesome symptoms of thyroid disorders may disrupt
one’s life if left untreated. Fortunately, there are good treatments available
for both hyperthyroidism and hypothyroidism. If you have any of the symptoms
listed in the discussion above, be sure to discuss them with your physician or
pharmacist. Likewise, if you have questions regarding medications used in the
treatment of thyroid disorders, please speak with your local pharmacist.
For more information on the thyroid gland, thyroid
disorders, treatment options, and thyroid cancer (which was not discussed
here), please visit http://www.thyroidawareness.com/.
Prepared
by: James Williams, UIC PharmD candidate, Class of 2012
