T3 & T4 Total

The thyroid hormones Triiodothyronine (T3) and Thyroxine (T4) are vital for controlling various physiological functions, including metabolism, growth, and energy expenditure. T3, (the active form) directly impacts various metabolic activities and helps control the body’s energy expenditure, while T4 acts as a precursor that is converted into T3 as needed. Both hormones are fundamental in sustaining the body’s metabolic rate, supporting cardiovascular health, aiding digestion, and facilitating muscle development. 

The T3 & T4 Total measures the total level (both free and bound forms) of the T3 and T4 hormones. T3, T4 levels can be influenced by various physiological factors, including age, pregnancy, body temperature, stress, nutritional status, exercise, circadian rhythms, and illness. Total T3 and T4  levels are also affected by changes in thyroxine binding globulin (TBG), the main transport protein for thyroid hormones. Pregnancy and estrogen therapy can elevate TBG levels (high total T3 and T4) while hyperandrogenism can lower TBG levels, (low total T3, T4) in absence of thyroid dysfunction. In such cases, levels of free T4, free T3 may be advised.

The T3 & T4 Total test is used to assess how well your thyroid gland is working and aid in the diagnosis and management of thyroid disorders, such as an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism). Your doctor may advise this test if you show any symptoms suggestive of hyperthyroidism, such as weight loss, nervousness, irritability, increased sweating, and rapid heartbeat, or hypothyroidism, such as weight gain, fatigue, sensitivity to cold, constipation, and dry skin. It is also important for pregnant women to have healthy amounts of thyroid hormones to ensure the healthy development of their babies. 

Fasting is not required for the T3 & T4 Total. Maintain the continuity of taking your thyroid medications on the day of the test unless otherwise advised by the doctor.

Test result ranges can vary slightly between labs due to differences in testing methods and reference intervals. Abnormal test results require expert interpretation; therefore, do not self-medicate at home solely based on these results and consult your doctor for proper understanding of the test results. Based on the results, your doctor will assess your medical condition, suggest lifestyle changes like diet and exercise, and decide if medication is needed to manage your condition.