What is a triiodothyronine (T3) test?

A triiodothyronine (T3) test measures the level of T3 in a sample of your blood. It's used to help diagnose thyroid disease.

Your thyroid is a small, butterfly-shaped gland at the base of your throat. It makes two hormones, T3 and T4 (thyroxine). Hormones are chemical messengers in your bloodstream that control the actions of certain cells or organs.

Thyroid hormones work together to control the way your body uses energy. They affect your weight, heart, body temperature, muscle strength, and even your mood. In children, thyroid hormones affect growth, too.

There are two forms of T3 in your blood:

• Free T3 is the active form that enters your tissues where it's needed.

• Bound T3 is attached to certain proteins which prevent it from entering your tissues. Most of your T3 is bound.

There are different tests for measuring T3:

• A total T3 test measures both bound and free T3 together. Medical experts think that this test is the more accurate way to measure T3.

• A free T3 test only measures free T3.

Other names: thyroid function test; total triiodothyronine, free triiodothyronine, FT3, TT3, radioimmunoassay FT3

What is it used for?

A T3 test is used to help:

• Diagnose hyperthyroidism, a condition in which your thyroid gland makes too much thyroid hormone. The test can also help find out what's causing the condition.

• Diagnose pituitary disorders. The pituitary is a pea-sized gland at the base of your brain. It makes a hormone called TSH (thyroid stimulating hormone). TSH tells the thyroid how much T3 and T4 to make. So, abnormal T3 levels may be a sign of a pituitary problem.

• Monitor treatment for thyroid disease, including hyperthyroidism and hypothyroidism, which is when the thyroid gland makes to little thyroid hormone.

T3 tests are usually ordered with blood tests that measure T4 and TSH (thyroid stimulating hormone) tests.

Why do I need a T3 test?

You may need a T3 test if you have symptoms of hyperthyroidism (too much thyroid hormone). Symptoms may include:

• Anxiety, nervousness, irritability

• Weight loss, even though your appetite may increase

• Shaky hands, muscle weakness

• Sweating or being very sensitive to heat

• Irregular heartbeat (arrhythmia)

• Frequent bowel movements (poops)

• Goiter (an enlarged thyroid gland)

• Trouble sleeping and fatigue

You may also need a T3 test if:

• You take thyroid hormone medicine to treat a thyroid problem. A T3 test can check whether you're taking the right dose to keep your thyroid hormone levels in a healthy range.

• You had abnormal results on a TSH and/or T4 test. Providers usually order these tests first to look into a possible thyroid disorder. If your test results are abnormal or unclear, your provider may use a T3 test to confirm or rule out hyperthyroidism.

T3 testing isn't commonly used to help check for hypothyroidism (too little thyroid hormone). That's because other thyroid tests can diagnose hypothyroidism earlier than a T3 test.

What happens during a T3 test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a T3 blood test. Certain medicines and supplements can affect your test results. Your provider will let you know if you need to stop taking any medicines before your test. But don't stop taking any medicines unless your provider tells you to.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

To understand the results of your T3 test, your provider will usually compare them with the results of your TSH and T4 tests. Like T3, T4 tests may measure either free or total T4, but providers usually measure free T4.

Your provider will look for different combinations of high, low, and normal results. Each combination suggests a different thyroid condition. Ask your provider to explain what your test results say about your health.

In general:

• Normal T3 levels (free or total) alone do not rule out thyroid disease. But if your TSH and free T4 levels are also normal, you probably don't have a thyroid condition.

• High T3 levels (free or total) may mean you have hyperthyroidism (too much thyroid hormone).

High T3 levels with:

• Low TSH and high free T4 levels may mean that a problem with your thyroid gland is causing too much thyroid hormone.

• Normal or high TSH and high free T4 levels may mean that a pituitary gland condition is causing too much thyroid hormone.

• Low T3 levels (free or total) may mean hypothyroidism (too little thyroid hormone).

Low or normal T3 levels with:

• High TSH levels and low free T4 levels may mean that a problem with your thyroid gland is causing too little thyroid hormone.

• Low TSH and low free T4 levels may mean that a pituitary gland condition is causing too little thyroid hormone.

What is a TSH Test?

TSH stands for thyroid stimulating hormone. A TSH test is a blood test that measures this hormone. TSH levels that are too high or too low may be a sign of a thyroid problem.

The thyroid is a small, butterfly-shaped gland in the front of your neck. Your thyroid makes hormones that control how your body uses energy. Thyroid hormones affect nearly every organ in your body, including your heart. They help control your weight, body temperature, muscle strength, and even your mood. If you don't have enough thyroid hormones in your blood, many of your body functions slow down. If you have too much, many body functions speed up.

Your thyroid is controlled by a gland in your brain, called the pituitary gland. The pituitary gland makes thyroid stimulating hormone (TSH). TSH tells your thyroid how much thyroid hormone it needs to make.

If the thyroid hormone levels in your blood are too low, your pituitary gland makes larger amounts of TSH to tell your thyroid to work harder. If your thyroid hormone levels are too high, the pituitary gland makes little or no TSH. By measuring TSH levels in your blood, you can find out if your thyroid is making the right level of hormones

What is it used for?

A TSH test is used to find out how well your thyroid is working. It can tell if you have hyperthyroidism (too much thyroid hormone) or hypothyroidism (too little thyroid hormone) in your blood. But a TSH test can't show what is causing a thyroid problem.

If you take prescription thyroid hormone medicine because of hypothyroidism or because you had your thyroid removed, you'll have regular TSH tests to check your thyroid hormone levels. TSH tests are also used to monitor your thyroid hormone levels after treatment for hyperthyroidism.

Why do I need a TSH test?

You may need a TSH test if you have symptoms of too much or too little thyroid hormone in your blood.

Hyperthyroidism (too much thyroid hormone) is also called overactive thyroid. Having more thyroid hormones than you need speeds up your body functions and causes symptoms that include:

• Weight loss, even though you may be eating more than usual

• Rapid or irregular heartbeat

• Feeling nervous or irritable

• Trouble sleeping, fatigue

• Shaky hands, muscle weakness

• Sweating or being very sensitive to heat

• Frequent bowel movements (pooping a lot)

• Goiter (enlarged thyroid)

Hypothyroidism (too little thyroid hormone) is also called underactive thyroid. Not having enough thyroid hormone slows down your body functions and causes symptoms that include:

• Fatigue

• Weight gain

• Being very sensitive to cold

• Joint and muscle pain

• Dry skin

• Dry, thinning hair

• Heavy or irregular menstrual periods

• Depression

• Constipation

You may also have a TSH test, along with other tests, to help diagnose unusual bumps or lumps on your thyroid that may be thyroid cancer or thyroid nodules (growths on your thyroid that aren't cancer).

What do the results mean?

Your TSH test results can tell you if your thyroid is making too much or too little thyroid. But the test can't explain why your TSH levels may be too high or too low.

If your test results aren't normal, your provider will probably order other thyroid blood tests to find out what's causing your thyroid problem. These blood tests may include:

• T4 thyroid hormone test

• T3 thyroid hormone test

• Thyroid antibodies test to help diagnose an autoimmune thyroid disorder, such as:

• Graves' disease, the most common cause of hyperthyroidism

• Hashimoto's disease, that the most common cause of hypothyroidism

In certain cases, an abnormal TSH result may be a sign of a pituitary gland problem, but this doesn't happen often

Is there anything else I need to know about a TSH test?

TSH levels may be high or low even when your thyroid gland is healthy. Serious illnesses not related to your thyroid may cause lower TSH levels for a short time. And TSH levels may be higher in people over age 80, even though they don't have any thyroid problems.

Pregnancy also affects TSH levels. They are often a little low during the first three months. But sometimes, thyroid disease develops during pregnancy. If you develop thyroid disease during pregnancy, your provider will monitor your condition through your pregnancy and after your baby is born. That's because hyperthyroidism, and less often, hypothyroidism, can continue after you give birth. If you have a history of thyroid disease, be sure to talk with your provider if you are pregnant or are thinking of becoming pregnant.

Newborn babies are routinely screened with a TSH test to see if they were born with hypothyroidism (congenital hypothyroidism).

What is HDL cholesterol?

HDL (high-density lipoprotein) is often referred to as “good” cholesterol. This is because it absorbs other types of cholesterol and carries them away from your arteries and back to your liver, which eliminates it from your body.

LDL (low-density cholesterol) is referred to as the ”bad“ cholesterol because it can build up on the walls of blood vessels, narrowing the passageways. If a blood clot forms and gets stuck in the narrowed passageway, it can cause a heart attack or stroke.

HDL is considered the “good” cholesterol because it helps get other types of cholesterol out of your body.

LDL is labeled the “bad” cholesterol because it can build up on your arterial wall and restrict blood flow. This build-up of cholesterol, along with plaque (inflammatory deposits), can result in atherosclerosis, also known as hardening or narrowing of the arteries. Atherosclerosis increases your risk for stroke, heart attack, and peripheral arterial disease (PAD).

What are the optimal levels of HDL cholesterol?

Cholesterol is measured through a blood test called a lipid panel. A lipid panel shows:

• Your total cholesterol

• LDL levels

• HDL levels

• VLDL levels and triglycerides

How can you boost your HDL cholesterol levels?

There are lifestyle changes you can make to increase your levels of HDL cholesterol, including:

• Physical activity. The American Heart Association (AHA) Trusted Source recommends a weekly minimum of 40 minutes of moderate intensity aerobic exercise 3 to 4 times weekly.

• Diet. Avoid trans fats (certain baked goods, fried foods, some margarines) and limit saturated fats (full-fat dairy, meats).

• Smoking. Try to stop smoking (tobacco products are known to lower HDL levels and increase LDL levels and triglycerides).

• Drinking. Avoid or limit alcoholic beverages (up to one drink a day for women of all ages and men older than age 65, and up to two drinks a day for men age 65 and younger).

HDL is known as the “good” cholesterol because takes the “bad” cholesterol (LDL) out of your arteries to reduce the chances of stroke, heart attack, and coronary artery disease (CAD).

Talk with a doctor about how often you should have your cholesterol level tested. Your doctor can also provide recommendations on boosting your HDL levels, with diet, exercise, and other lifestyle changes.

what causes low blood pressure?

Low blood pressure is generally considered a blood pressure reading lower than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic).

What's considered low blood pressure for one person might be OK for someone else. Low blood pressure might cause no noticeable symptoms, or it might cause dizziness and fainting. Sometimes, low blood pressure can be life-threatening.

The causes of low blood pressure range from dehydration to serious medical conditions. It's important to find out what's causing low blood pressure so that it can be treated, if necessary.

Types

Types of low blood pressure include:

• Orthostatic hypotension (postural hypotension). This is a sudden drop in blood pressure when standing from a sitting position or after lying down. Causes include dehydration, long-term bed rest, pregnancy, certain medical conditions and some medications. This type of low blood pressure is common in older adults.

• Postprandial hypotension. This drop in blood pressure occurs 1 to 2 hours after eating. It's most likely to affect older adults, especially those with high blood pressure or autonomic nervous system diseases such as Parkinson's disease. Eating small, low-carbohydrate meals, drinking more water, and avoiding alcohol might help reduce symptoms.

• Neurally mediated hypotension. This is a blood pressure drop that happens after standing for long periods. This type of low blood pressure mostly affects young adults and children. It might result from miscommunication between the heart and the brain.

• Multiple system atrophy with orthostatic hypotension. Also called Shy-Drager syndrome, this rare disorder affects the nervous system that controls involuntary functions such as blood pressure, heart rate, breathing and digestion. It's associated with having very high blood pressure while lying down.

Symptoms

Low blood pressure (hypotension) symptoms may include:

• Blurred or fading vision

• Dizziness or lightheadedness

• Fainting

• Fatigue

• Trouble concentrating

• Nausea

For some people, low blood pressure may be a sign of an underlying health condition, especially when it drops suddenly or occurs with symptoms.

A sudden fall in blood pressure can be dangerous. A change of just 20 mm Hg — a drop from 110 mm Hg systolic to 90 mm Hg systolic, for example — can cause dizziness and fainting. And big drops, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening.

Extreme low blood pressure can lead to a condition known as shock. Symptoms of shock include:

• Confusion, especially in older people

• Cold, clammy skin

• Decrease in skin coloration (pallor)

• Rapid, shallow breathing

• Weak and rapid pulse

When to see a doctor

If you have symptoms of extreme low blood pressure (hypotension) or shock, seek emergency medical help.

Most health care providers consider blood pressure to be too low only if it causes symptoms. Occasional minor dizziness or lightheadedness can be caused by many things, such as spending too much time in the sun or in a hot tub. It's important to see a health care provider to get a correct diagnosis.

If you have consistently low blood pressure readings but feel fine, your provider may just monitor you during routine health checkups. It can be helpful to keep a record of your symptoms, when they occur and what you're doing at the time.

• pressure.

• Lack of nutrients in the diet. Low levels of vitamin B-12, folate and iron can keep the body from producing enough red blood cells (anemia), which can lead to low blood pressure.

Medications that can cause low blood pressure

Some medications can cause low blood pressure, including:

• Water pills (diuretics), such as furosemide (Lasix) and hydrochlorothiazide (Microzide)

• Alpha blockers, such as prazosin (Minipress)

• Beta blockers, such as atenolol (Tenormin) and propranolol (Inderal, Innopran XL, Hemangeol)

• Drugs for Parkinson's disease, such as pramipexole (Mirapex) or those containing levodopa

• Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor) and imipramine (Tofranil)

• Drugs for erectile dysfunction, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Alyq, Cialis), particularly when taken with the heart medication nitroglycerin (Nitrostat, Nitro-Dur, Nitromist)

Risk factors

Anyone can have low blood pressure (hypotension). Risk factors for hypotension include:

• Age. Drops in blood pressure on standing or after eating occur primarily in adults older than 65. Neurally mediated hypotension primarily affects children and younger adults.

• Medications. Certain medications, including some blood pressure drugs, increase the risk of low blood pressure.

• Certain diseases. Parkinson's disease, diabetes and some heart conditions may increase risk of low blood pressure.

Complications

Potential complications of low blood pressure (hypotension) include:

• Dizziness

• Weakness

• Fainting

• Injury from falls

Severely low blood pressure can reduce the body's oxygen levels, which can lead to heart and brain damage.

When to worry about high blood pressure?

Blood pressure is a term used to describe the measurement of force exerted by the blood against the walls of the blood vessels. The heart pumps pure blood through the arteries from the heart to different parts of the body. Elevated blood pressure is also known as hypertension. High blood pressure is considered as an abnormal condition as it makes it harder for the heart to pump blood from the heart to other parts of the body. This can lead to development of other conditions such as arteriosclerosis (hardening of the arteries), stroke, kidney disease and heart failure.

In medical terms, blood pressure is expressed with a top number called as systolic pressure and a bottom number called as diastolic pressure. The standard unit for measuring blood pressure is mmHg. The clinical importance of blood pressure values are as follows:

• <120/80 mm/hg – Normal

• Between 120/80 to 139/89 mmHg – Prehypertension

• Between 140/90 to 159/99 mmHg – Stage 1 high blood pressure

• >160/100 mmHg – Stage 2 high blood pressure

• High blood pressure in people above 60 years of age : >150/90 mmHg

Under normal circumstances, it is advised to consult a physician when the blood pressure numbers are above or below the normal limits. In case of any major deviations from the normal blood pressure, it is a warning sign and requires immediate medical attention.

When to Worry about High Blood Pressure?

It is advised to seek medical advice immediately if the patient with high blood pressure does not respond to treatment prescribed by the doctor and the blood pressure still appears to be above normal limits. If 2 to 3 consecutive readings appear higher than normal, the condition needs to be evaluated as there may be other underlying conditions such as kidney issues, excess production of hormones, blood vessels blockage, thyroid issues etc. which makes one worry.

It is also advised to consult a physician at the earliest if symptoms such as fatigue, shortness of breath, light-headedness, headache, nausea, visual disturbances, and confusion develop in association with elevation in blood pressure. These may occur due to side effects of certain medication or it may be due to drug interaction with other regular medication. It may be needed to evaluate the condition, followed by discontinuation of a medication, or change in dosage of a medication, or switching over to a newer medication.

Resistant high blood pressure or resistant hypertension is a condition where the blood pressure is above normal limits even after taking medication and lifestyle modification. It occurs in about 20 to 30 percent of cases diagnosed with hypertension. The most possible causes of this condition are as follows:

• Underlying Risk Factors for Resistant High Blood Pressure: Poor control of underlying conditions such as obesity and diabetes leads to high blood pressure.

• Irregular Medication: If the prescribed medications are not taken as directed; i.e. incorrect dosage of medication, skipping medication or discontinuing without physicians approval, it can lead to alteration in blood pressure.

• Intake of Salt and Alcohol: It has been seen that in people with high blood pressure, unrestricted intake of salt and alcohol can lead to further elevation of blood pressure.

• Drug Interaction: Certain over the counter drugs such as pain relievers, decongestants and certain herbal compounds interfere with high blood pressure control.

• Presence of Underlying Health Issue: Presence of certain medical conditions such as sleep apnea, adrenal disorder, kidney issues can also lead to resistant blood pressure.

If any of the causes of resistant blood pressure persists and the person encounters high blood pressure, it is a serious thing to be worried about and one must seek immediate medical help.

How to Control High Blood Pressure?

High blood pressure is generally a treatable condition. In most of the cases, the following are recommended for controlling the high blood pressure:

• Quit smoking

• Encouraged to lose weight

• Limit alcohol and caffeine intake

• Exercise regularly and follow a healthy lifestyle

• Follow a healthy diet and limit salt intake in diet

• Reduce stress

In addition to the above, certain anti-hypertensive drugs may be prescribed by the doctor based on the condition of the patient.

What is VLDL cholesterol?

VLDL stands for very-low-density lipoprotein. Your liver makes VLDL and releases it into your bloodstream. The VLDL particles mainly carry triglycerides, another type of fat, to your tissues. VLDL is similar to LDL cholesterol, but LDL mainly carries cholesterol to your tissues instead of triglycerides.

VLDL and LDL are sometimes called "bad" cholesterols because they can contribute to the buildup of plaque in your arteries. This buildup is called atherosclerosis. The plaque that builds up is a sticky substance made up of fat, cholesterol, calcium, and other substances found in the blood. Over time, the plaque hardens and narrows your arteries. This limits the flow of oxygen-rich blood to your body. It can lead to coronary artery disease and other heart diseases.

How do I know what my VLDL level is?

There isn't a way to directly measure your VLDL level. Instead, you will most likely get a blood test to measure your triglyceride level. The lab can use your triglyceride level to estimate what your VLDL level is. Your VLDL is about one-fifth of your triglyceride level. However, estimating your VLDL this way does not work if your triglyceride level is very high.

What should my VLDL level be?

Your VLDL level should be less than 30 mg/dL (milligrams per deciliter). Anything higher than that puts you at risk for heart disease and stroke.

How can I lower my VLDL level?

Since VLDL and triglycerides are linked, you can lower VLDL level by lowering your triglyceride level. You may be able to lower your triglycerides with a combination of losing weight, diet, and exercise. It is important to switch to healthy fats, and cut back on sugar and alcohol. Some people may also need to take medicines.

What does a cortisol test tell you?

A cortisol level test uses a blood sample to measure the level of cortisol in your blood.

Cortisol is a steroid hormone released by the adrenal glands. The adrenal glands sit on top of your kidneys. A cortisol level test may also be called a serum cortisol test.

What is cortisol?

Cortisol is a steroid hormone produced by the adrenal glands. Whenever you experience something your body perceives as a threat, like a large dog barking at you, a chemical known as adrenocorticotropic hormone (ACTH) is released in your brain. This triggers your adrenal glands to release cortisol and adrenaline.

Cortisol is the main hormone involved in stress and the fight, flight, or freeze response. This is a natural and protective response to a perceived threat or danger. Increased levels of cortisol result in a burst of new energy and strength.

In the fight, flight, or freeze response, cortisol suppresses any functions that are unnecessary or detrimental to that response. During a fight, flight, or freeze response, you can have:

• a rapid heart rate

• dry mouth

• stomach upset

• diarrhea

• panic

Cortisol release also:

• suppresses your growth processes

• suppresses your digestive system

• suppresses your reproductive system

• changes how your immune system responds

Why is the cortisol level test performed?

The cortisol level test checks whether your cortisol production levels are too high or too low. Certain conditions, such as Addison’s disease and Cushing’s disease, affect the amount of cortisol your adrenal glands produce.

The test is used in the diagnosis of these diseases and as a way to assess the functioning of the adrenal and pituitary glands.

Cortisol plays a role in several systems in the body, including:

• stress responses

• immune system

• nervous system

• circulatory system

• skeletal system

• the breakdown of proteins, fats, and carbohydrates.

How to prepare for the cortisol level test

Cortisol levels vary throughout the day but are usually highest in the morning. Your doctor will usually request that the test be done in the morning. You don’t need to fast for a cortisol test.

Certain drugs affect cortisol levels. Your doctor may request that you not take these drugs before the test is done. Cortisol levels are sometimes increased by:

• drugs containing estrogen

• synthetic glucocorticoids, such as prednisone

• pregnancy

Cortisol levels are sometimes decreased by:

• drugs containing androgens

• phenytoin

Cortisol levels can also be affected by physical and emotional stress and illness. This is due to the increased release of ACTH by the pituitary gland during the usual stress response.

What do the results of the cortisol level test mean?

Standard results for a blood sample taken at 8 a.m. range between 6 and 23 micrograms per deciliter (mcg/dL). Many laboratories have different measuring techniques, and what’s considered standard may vary.

Higher-than-usual cortisol levels may indicate that:

• your pituitary gland is releasing too much ACTH due to a tumor or excess growth of the pituitary gland

• you have a tumor in your adrenal gland, resulting in excess cortisol production

• you have a tumor elsewhere in your body that’s involved in cortisol production

Lower-than-usual cortisol levels may indicate that:

• you have Addison’s disease, which occurs when the production of cortisol by your adrenal glands is too low

• you have hypopituitarism, which occurs when the production of cortisol by your adrenal glands is too low because the pituitary gland is not sending proper signals