Download Practice -5

COLLEGE OF HEALTH SCIENCES – HAIL
Medical laboratory Dept.- Second term
THIRD YEAR – Hormones& Endocrinology
Practice 5
T3
Triiodothyronine (T3) is a thyroid hormone. It plays an important role in the body's
control of metabolism.
A laboratory test can be done to measure the amount of T3 in your blood.
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of
the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care
provider wraps an elastic band around the upper arm to apply pressure to the area and
make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects
into an airtight vial or tube attached to the needle. The elastic band is removed from
your arm. Once the blood has been collected, the needle is removed, and the puncture
site is covered to stop any bleeding.
Prepared By Dr. Abdelrahman Elresheid1
In infants or young children, a sharp tool called a lancet may be used to puncture the
skin and make it bleed. The blood collects into a small glass tube called a pipette, or
onto a slide or test strip. A bandage may be placed over the area if there is any
bleeding.
How to Prepare for the Test
Your health care provider will instruct you, if necessary, to stop taking drugs that may
interfere with the test.
Drugs that can increase T3 measurements include:




Birth control pills
Clofibrate
Estrogens
Methadone
Drugs that can decrease T3 measurements include:






Anabolic steroids
Androgens
Antithyroid drugs (for example, propylthiouracil)
Lithium
Phenytoin
Propranolol
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while
others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
This test is done as part of an evaluation of thyroid function. Your doctor may order this
test if you have signs of a thyroid disorder. Thyroid function is complex and depends on
the action of many different hormones, including thyroid-stimulating hormone (TSH) and
T4.
Sometimes it can be useful to measure both T3 and T4 when looking at thyroid function.
For example, in some cases of hyperthyroidism, T3 may be increased but T4 may be
normal.
The T3 test can measure both the T3 that is attached to proteins and floating free in the
blood.
Normal Results
Prepared By Dr. Abdelrahman Elresheid2
The range for normal values is 100 to 200 ng/dL (nanograms per deciliter).
Normal value ranges may vary slightly among different laboratories. Talk to your doctor
about the meaning of your specific test results.
What Abnormal Results Mean
Greater than normal levels may indicate:




High levels of a protein that carries T3 in the blood (may occur in pregnancy, with
use of birth control pills or estrogen, liver disease, or as part of an inherited
condition)
Hyperthyroidism (for example, Graves disease)
T3 thyrotoxicosis (rare)
Thyroid cancer (rare)
Lower than normal levels may be due to:



Long-term illness
Hypothyroidism (for example, Hashimoto's disease)
Starvation
Other conditions under which the test may be performed:



Painless (silent) thyroiditis
Thyrotoxic periodic paralysis
Toxic nodular goiter
Risks
Veins and arteries vary in size from one patient to another and from one side of the
body to the other. Obtaining a blood sample from some people may be more difficult
than from others.
Other risks associated with having blood drawn are slight but may include:




Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Considerations
Pregnancy and liver disease will falsely raise the T3 level. In these cases, it is useful to
measure either the free T3 level or to perform the T3RU test.
Prepared By Dr. Abdelrahman Elresheid3
Alternative Names
Triiodothyronine; T3 radioimmunoassay
T4 test
T4 (thyroxine) is a hormone produced by the thyroid gland. A laboratory test can be
done to measure the amount of T4 in your blood.
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of
the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care
provider wraps an elastic band around the upper arm to apply pressure to the area and
make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects
into an airtight vial or tube attached to the needle. The elastic band is removed from
your arm. Once the blood has been collected, the needle is removed, and the puncture
site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the
skin and make it bleed. The blood collects into a small glass tube called a pipette, or
onto a slide or test strip. A bandage may be placed over the area if there is any
bleeding.
How to Prepare for the Test
Your health care provider will tell you, if necessary, to stop taking drugs that may
interfere with the test.
Drugs that can increase T4 measurements include:



Birth control pills
Clofibrate
Estrogens
Prepared By Dr. Abdelrahman Elresheid4

Methadone
Drugs that can decrease T4 measurements include:








Anabolic steroids
Androgens
Antithyroid drugs (for example, propylthiouracil and methimazole)
Interferon alpha
Interleukin-2
Lithium
Phenytoin
Propranolol
This list may not include all medications.
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while
others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
This test is done as part of an evaluation of thyroid function. Your doctor may order this
test if you have signs of a thyroid disorder. Thyroid function is complex and depends on
the action of many different hormones, including thyroid-stimulating hormone (TSH) and
T3 (triiodothyronine).
T4 levels are important, because T4 increases numerous substances that produce
energy for the body.
Most T4 is transported by proteins. If T4 is not attached to a protein, it is called "free"
T4.
Conditions under which the test may be performed:




Hypopituitarism
Hypothyroidism - primary
Hypothyroidism - secondary
Thyrotoxic periodic paralysis
Normal Results
A typical normal range is 4.5 to 11.2 micrograms per deciliter (mcg/dL).
Normal value ranges may vary slightly among different laboratories. Talk to your doctor
about the meaning of your specific test results.
Prepared By Dr. Abdelrahman Elresheid5
What Abnormal Results Mean
Greater than normal levels of T4 along with low levels of TSH may be due to conditions
that involve an overactive thyroid, including:








Early Hashimoto's disease
Graves disease
Germ cell tumors
High levels of the protein that carries T4 in the blood (can occur with pregnancy,
use of birth control pills or estrogen, liver disease, and as part of an inherited
condition)
Iodine-induced hyperthyroidism
Subacute or chronic thyroiditis
Toxic multinodular goiter
Trophoblastic disease
Lower than normal levels of T4 may indicate:




Hypothyroidism (including Hashimoto's disease and several other disorders
involving an underactive thyroid)
Illness
Malnutrition or fasting
Use of certain medications
Risks
Veins and arteries vary in size from one patient to another and from one side of the
body to the other. Obtaining a blood sample from some people may be more difficult
than from others.
Other risks associated with having blood drawn are slight but may include:




Excessive bleeding
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Alternative Names
Thyroxine test
Practice 3
Prepared By Dr. Abdelrahman Elresheid6
TSH
TSH is a laboratory test that measures the amount of thyroid stimulating hormone (TSH)
in your blood. TSH is produced by the pituitary gland and tells the thyroid gland to make
and release the hormones thyroxine (T4) and triiodothyronine (T3).
How the Test is Performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of
the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care
provider wraps an elastic band around the upper arm to apply pressure to the area and
make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects
into an airtight vial or tube attached to the needle. The elastic band is removed from
your arm. Once the blood has been collected, the needle is removed, and the puncture
site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the
skin and make it bleed. The blood collects into a small glass tube called a pipette, or
onto a slide or test strip. A bandage may be placed over the area if there is any
bleeding.
How to Prepare for the Test
Your health care provider may ask you to stop taking drugs that may interfere with the
test. Drugs that can affect TSH measurements include:






Amiodarone
Antithyroid medications
Dopamine
Lithium
Potassium iodide
Prednisone
How the Test Will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while
others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the Test is Performed
Prepared By Dr. Abdelrahman Elresheid7
Your doctor will order this test if you have signs of abnormal thyroid function
(hyperthyrodism or hypothyrodism). It is also used to monitor treatment of these
conditions.
Normal Results
Normal values are 0.4 - 4.0 mIU/L.
However, those without signs or symptoms of an underactive thyroid who have a TSH
value over 2.0 mIU/L but normal T4 levels may develop hypothyroidism in the future.
This is called subclinical hypothyroidism (mildly underactive thyroid) or early-stage
hypothyroidism. Anyone with a TSH value above this level should be followed very
closely by a doctor.
If you are being treated for a thyroid disorder, your TSH level should be between 0.5
and 3.0 mIU/L.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor
about the meaning of your specific test results.
What Abnormal Results Mean
Greater than normal levels may indicate:





Congenital hypothyroidism (cretinism)
Exposure to mice (lab workers or veterinarians)
Primary hypothyroidism
Thyroid hormone resistance
TSH-dependent hyperthyroidism
Lower than normal levels may be due to:



Hyperthyroidism
TSH deficiency
Use of certain medications (including dopamine agonists, glucocorticoids,
somatostatin analogues, and bexarotene)
Risks
Veins and arteries vary in size from one patient to another and from one side of the
body to the other. Obtaining a blood sample from some people may be more difficult
than from others.
Other risks associated wit having blood drawn are slight but may include:

Excessive bleeding
Prepared By Dr. Abdelrahman Elresheid8



Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Alternative Names
Thyrotropin; Thyroid stimulating hormone
Prepared By Dr. Abdelrahman Elresheid9