Breaking News
January 20, 2018 - Morning Break: Missing Maria Deaths; N.J. Doc Charged in Wife’s Murder; Viva Vaseline!
January 20, 2018 - No interventions proven to prevent late-life dementia
January 20, 2018 - Judge orders new Olympus trial over superbug death
January 20, 2018 - Don’t Rely on Just One Blood Pressure Test for Kids: Study
January 20, 2018 - Going Off the Deep End About Water
January 20, 2018 - Parental attention can reduce risk of drug abuse in adolescence
January 20, 2018 - Mast Uri System offers efficient and cost-friendly diagnostic solution
January 20, 2018 - International SOS, Chatham House sign partnership agreement to further advance Global Health Security Agenda
January 20, 2018 - Study offers way to predict onset of lung disease in children with cystic fibrosis
January 20, 2018 - C-Suite Must Lead in Ending Sexual Harassment
January 20, 2018 - Researchers find a way to ‘starve’ cancer
January 20, 2018 - Applied math can help predict genesis and evolution of different cancers
January 20, 2018 - UCLA researchers describe herpes virus structure associated with Kaposi’s sarcoma
January 20, 2018 - New study enrolls first patient to evaluate potential of WaveCrest LAAO System
January 20, 2018 - New review explores effects of exposing developing brains to general anesthesia
January 20, 2018 - GW Pharmaceuticals Announces Acceptance of NDA Filing for Epidiolex (cannabidiol) in the treatment of Lennox-Gastaut syndrome and Dravet syndrome
January 20, 2018 - Weight-Loss Surgery Approaches Offer Similar Results
January 20, 2018 - Free online access to millions of documents on chemical toxicity
January 20, 2018 - CE marked MAST Toxoreagent kit for detection of Toxoplasma antibodies
January 20, 2018 - DNA study sheds light on longstanding puzzle of cell division
January 20, 2018 - Montefiore provides specialized medical care to parents of adopted children
January 20, 2018 - Enzyme discovery provides new horizon of therapeutic opportunities across disease spectrum
January 20, 2018 - New smartphone app successfully enables remote monitoring of surgical wounds
January 20, 2018 - Liquid Biopsy Shows Promise for Colon Cancer
January 20, 2018 - Surgery death rates in Africa are twice global average: study
January 20, 2018 - New isothermal amplification kit using LAMP technology
January 20, 2018 - Pretreatment improves outcomes in high-risk stage 3 melanoma, study shows
January 20, 2018 - Health Highlights: Jan. 17, 2018
January 20, 2018 - House Opioid Task Force has Big Plans for 2018
January 20, 2018 - Perfectionism among young people significantly increased since 1980s, study finds
January 20, 2018 - Evidensia Sweden orders Sectra cloud-based PACS for reviewing all medical images
January 20, 2018 - Researchers test new anti-malaria medication
January 20, 2018 - Small Joint Surgeries Drop among RA Patients
January 20, 2018 - Young people with shared residency have fewer mental problems
January 20, 2018 - Childhood physical activity may have far-reaching implications
January 20, 2018 - Overweight female kidney donors of childbearing age may have greater preeclampsia risk
January 20, 2018 - MSU scientists seek to identify brain mechanisms related to psychosis
January 20, 2018 - CBT is cost-effective treatment in primary care setting, Kaiser Permanente study finds
January 20, 2018 - Scientists find how potential new eczema treatment could also alleviate asthma
January 20, 2018 - Older hospitalized patients less likely to be tested for influenza
January 20, 2018 - Syndax Pharmaceuticals Announces Clinical Collaboration to Evaluate Entinostat in Combination with anti-PD-L1 Cancer Immunotherapy in Breast Cancer
January 20, 2018 - Endoscopes Over Microscopes in Retinal Surgery: Ophthalmology Times
January 20, 2018 - Technology not taking over children’s lives despite screen-time increase
January 20, 2018 - Study finds extensive contamination around lead battery recycling plants in 7 African countries
January 20, 2018 - Flu may pass to others through exhaled breath, study shows
January 20, 2018 - Neuronal loss very limited in Alzheimer’s disease, new study shows
January 20, 2018 - Novel robot can aid treatment of rare birth defect
January 19, 2018 - TherapeuticsMD Announces Submission of New Drug Application for TX-001HR
January 19, 2018 - Fighting Infant Mortality | Medpage Today
January 19, 2018 - Researchers offer new evidence on four-year-old children’s knowledge about ecology
January 19, 2018 - Analysis finds overlooked crucial factor in determining prognosis for DIPGs
January 19, 2018 - Review explores consequences of genetic testing and cancer risk-reducing surgery
January 19, 2018 - Morning Break: HHS Div. of Religious Freedom; Trump’s Heart Health; Minister of Loneliness
January 19, 2018 - Parkinson’s disease ‘jerking’ side effect detected by algorithm
January 19, 2018 - New analysis finds dramatic increases in maternal mortality rates
January 19, 2018 - Study provides more evidence for link between increased cancer risk and advanced gum disease
January 19, 2018 - Study reveals key mechanism of how cancer metastasis happens
January 19, 2018 - Weight-Loss Surgery’s Benefits Wane Over Time for Diabetics
January 19, 2018 - Cath Lab Recap: Sapien 3 Delivery System Recall; Transatlantic PCI Smackdown
January 19, 2018 - Parkinson’s treatment could be more effective, student finds
January 19, 2018 - New vaccine approach offers effective protection against tuberculosis
January 19, 2018 - Home care agencies often wrongly deny Medicare help to the chronically ill
January 19, 2018 - One hundred percent fruit juice does not alter blood sugar levels
January 19, 2018 - Prebiotics could enhance learning and memory skills in infants
January 19, 2018 - CMS May Cover MRI With Cardiac Devices Across the Board
January 19, 2018 - As income rises, women get slimmer—but not men
January 19, 2018 - Researchers develop adhesive materials to prevent bracket stains on teeth
January 19, 2018 - Flu can be spread without coughs and sneezes
January 19, 2018 - AMSBIO’s new recombinant protein shows great promise for organoid culture
January 19, 2018 - AbbVie’s Upadacitinib Granted Breakthrough Therapy Designation from the U.S. Food and Drug Administration for Atopic Dermatitis
January 19, 2018 - ASH: Pomalidomide Dose Escalation Improves Response
January 19, 2018 - AMSBIO offers isogenic panels of neuronal iPSC derivatives
January 19, 2018 - Is your child’s school an obesity risk?
January 19, 2018 - Scientists describe groundbreaking training effect on the innate immune system
January 19, 2018 - MAST announces new AmpC, ESBL & Carbapenemase Detection Set
January 19, 2018 - Signaling molecules likely involved in concussions, rodent studies show
January 19, 2018 - Mast introduces Carba plus for CPE and OXA-48 confirmation
January 19, 2018 - Paleolithic diet helps overweight women maintain weight loss
January 19, 2018 - Agios Submits New Drug Application to the FDA for Ivosidenib for the Treatment of Patients with Relapsed/Refractory AML and an IDH1 Mutation
January 19, 2018 - This Flu Season, Don’t Forget About Tamiflu
Thyroxine (T4) Test: MedlinePlus Lab Test Information

Thyroxine (T4) Test: MedlinePlus Lab Test Information

image_pdfDownload PDFimage_print

What is a Thyroxine (T4) Test?

A thyroxine test helps diagnose disorders of the thyroid. The thyroid is a small, butterfly-shaped gland located near the throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. Thyroxine, also known as T4, is a type of thyroid hormone. This test measures the level of T4 in your blood. Too much or too little T4 can indicate thyroid disease.

The T4 hormone comes in two forms:

  • Free T4, which enters the body tissues where it’s needed
  • Bound T4, which attaches to proteins, preventing it from entering body tissues

A test that measures both free and bound T4 is called a total T4 test. Other tests measure just free T4. A free T4 test is considered more accurate than a total T4 test for checking thyroid function.

Other names: free thyroxine, free T4, total T4 concentration, thyroxine screen, free T4 concentration

What is it used for?

A T4 test is used to evaluate thyroid function and diagnose thyroid disease.

Why do I need a thyroxine test?

Thyroid disease is much more common in women and most often occurs under the age of 40. It also tend to run in families. You may need a thyroxine test if a family member has ever had thyroid disease or if you have symptoms of having too much thyroid hormone in your blood, a condition called hyperthyroidism, or symptoms of having too little thyroid hormone, a condition called hypothyroidism.

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

  • Anxiety
  • Weight loss
  • Tremors in the hands
  • Increased heart rate
  • Puffiness
  • Bulging of the eyes
  • Trouble sleeping

Symptoms of hypothyroidism, also known as underactive thyroid, include:

  • Weight gain
  • Fatigue
  • Hair loss
  • Low tolerance for cold temperatures
  • Irregular menstrual periods
  • Constipation

What happens during a thyroxine 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 thyroxine blood test. If your health care provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

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?

Your results may come in the form of total T4, free T4, or a free T4 index.

  • The free T4 index includes a formula that compares free and bound T4.
  • High levels of any of these tests (total T4, free T4, or free T4 index) may indicate an overactive thyroid, also known as hyperthyroidism.
  • Low levels of any of these tests (total T4, free T4, or free T4 index) may indicate an underactive thyroid, also known as hypothyroidism.

If your T4 test results are not normal, your health care provider will likely order more thyroid tests to help make a diagnosis. These may include:

  • T3 thyroid hormone tests. T3 is another hormone made by the thyroid.
  • A TSH (thyroid stimulating hormone) test. TSH is a hormone made by the pituitary gland. It stimulates the thyroid to produce T4 and T3 hormones.
  • Tests to diagnose Graves’ disease, an autoimmune disease that causes hyperthyroidism
  • Tests to diagnose Hashimoto’s thyroiditis, an autoimmune disease that causes hypothyroidism

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

Thyroid changes can happen during pregnancy. These changes are usually not significant, but some women can develop thyroid disease during pregnancy. Hyperthyroidism happens in about one in every 500 pregnancies, while hypothyroidism happens in approximately one in every 250 pregnancies. Hyperthyroidism, and less often, hypothyroidism, may remain after pregnancy. If you develop a thyroid condition during pregnancy, your health care provider will monitor your condition after your baby is born. Also, if you have a history of thyroid disease, be sure to talk with your health care provider if you are pregnant or are thinking of becoming pregnant.

Tagged with:

About author

Related Articles