Total T4 in Dehradun

What is a Total T4?

Thyroxine, or T4, is the principal hormone the thyroid gland secretes, and it sets the metabolic pace of nearly every tissue in the body. Most of it acts as a reservoir: tissues convert T4 into the more active T3 as they need it, so T4 represents supply while T3 represents use. Total T4 measures all the thyroxine present, both the small unbound fraction that is biologically active and the much larger portion travelling bound to carrier proteins. That is the measurement's main limitation and the reason free T4 exists. Anything that changes carrier-protein levels changes the total without altering thyroid function at all, and several common situations do exactly that: pregnancy, the contraceptive pill and oestrogen therapy raise carrier proteins and so raise total T4, while serious illness, liver disease and certain medicines lower them. In those circumstances a total T4 can read abnormal in someone whose thyroid is working perfectly, or normal in someone whose thyroid is not. Read alongside TSH it remains a serviceable part of a thyroid profile, but where carrier proteins are likely disturbed, free T4 is the more dependable measure.

Why take this test?

A T4 test is advised as part of a thyroid profile when TSH is abnormal, to confirm the finding and grade how marked it is, and when thyroid symptoms are present: unexplained tiredness, weight gain or loss without a change in diet, hair fall, dry skin, feeling unusually cold or unusually hot, constipation, palpitations, tremor, anxiety, low mood, irregular periods or difficulty conceiving. It is used to monitor treatment, both to check a thyroxine dose and to follow anti-thyroid medicines, and it is particularly informative in suspected overactivity where TSH is suppressed. In pregnancy, and in anyone on the contraceptive pill or oestrogen therapy, your doctor will often prefer free T4 for the reasons above. Thyroid disorders are notably common across the sub-Himalayan belt that includes Uttarakhand and affect women several times more often than men, so long-running vague symptoms in this region are worth testing rather than dismissing.

• An abnormal TSH result needing confirmation
• Tiredness, weight change, hair fall or dry skin
• Feeling unusually cold or unusually hot
• Palpitations, tremor, anxiety or low mood
• Monitoring a thyroxine dose or anti-thyroid treatment
• Irregular periods or difficulty conceiving

Normal reference ranges

Ranges are indicative for adults. Your report carries the lab-specific reference range and is reviewed by a LabONE pathologist; always interpret results with your doctor.

FAQs: Total T4 in Dehradun