A healthy result should fall into the range 4.5 - 12 ug/dL, or 57.92 - 154.46 nmol/L.
Thyroxine (T4) is a hormone produced by the thyroid gland. It is sometimes called total thyroxine because it includes both free T4 and T4 bound to proteins. Thyroxine is only one-tenth as potent as the other major thyroid hormone, triiodothyronine (T3). Moreover, the portion of thyroxine that is biologically active is free T4, that is, the portion of T4 that is not bound to proteins in the blood. Greater than 99% of thyroxine is bound to serum proteins. Thyroxine acts on almost every cell in the body. It sets the metabolic tone of cells. Thyroxine is critically important for the growth and development of fetuses, neonates, and children. The thyroid gland produces and stores thyroxine until it is needed for release. The thyroid gland releases T4 when it is stimulated by thyroid-stimulating hormone, also known as TSH or thyrotropin. Free thyroxine is often more useful than total thyroxine (total T4) in assessing thyroid function, but total T4 can be a useful biomarker in some cases.
Normal Ranges for Total T4:
0-5 days: 5.0-18.5 mcg/dL
6 days-2 months: 5.4-17.0 mcg/dL
3-11 months: 5.7-16.0 mcg/dL
1-5 years: 6.0-14.7 mcg/dL
6-10 years: 6.0-13.8 mcg/dL
11-19 years: 5.9-13.2 mcg/dL
Decreased thyroxine levels in the serum usually indicate hypothyroidism or chronic or subacute thyroiditis. Abnormally low thyroxine may cause symptoms of hypothyroidism including weakness and fatigue, cold intolerance, shortness of breath, weight gain, constipation, cognitive problems, dry skin, hoarseness, and swelling (edema).
Some specific causes of low thyroxine are:
Elevated thyroxine levels may indicate hyperthyroidism, thyroid hormone resistance syndrome, or thyroxine toxicosis. Elevated thyroxine may cause symptoms of hyperthyroidism including excessive appetite, anxiety, heart palpitations, sweating, shortness of breath, weight loss, and intolerance to heat.
Some specific causes of high thyroxine are:
$15 per monthSelect this plan
$59 per yearSelect this plan
$250 single paymentSelect this plan
Health is not exactly rocket science. You just have to know what your body needs and doesn't need. Your medical tests contain that information. Upload them to our service and we’ll help you understand organize, and act on them.Get Started
"I was really concerned about my lab results and my GP was not able to see me for another week. Through HealthMatters I was able to interpret my results instantly."
"I've been keeping all my lab results in a spreadsheet, covering approximately 20 years. The HealthMatters team helped me upload that info into the cloud. I can show this data to my family and doctors now easily."
"I had no idea what my lab results meant. Here I found all the biomarkers that I was looking for online. Finally, I have not only organized them all neatly in one place, but I am also grateful to be able to understand what they mean."