A Thyroid Function Test (TFT) is a series of blood tests that are used to evaluate the condition of your thyroid gland. Situated in the neck, the thyroid gland produces hormones T3 (Triiodothyronine), T4 (Thyroxine) and Calcitonin, which regulate the metabolic rate and calcium levels in the body. Commonly employed tests are T4, TSH (Thyroid Stimulating Hormone made by the pituitary gland) and T3. These thyroid function tests are used to determine whether a patient is suffering from hyper- or hypothyroidism and the corresponding TSH levels.
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How Does A Doctor Diagnose Hypothyroidism?
Hypothyroidism is examined by an endocrinologist usually. The patient’s symptoms and blood tests are taken into account when determining an under-active thyroid diagnosis. This holistic approach is important in making the correct diagnosis and gauging the intensity of the issue.
The doctor also takes into account the medical history of the patient and his family and the results of physical examination. This is where the hormones TSH, T3, and T4 come into play.
Medical History
Providing your doctor all the details is imperative. Compile all the information you can from your immediate family members. Get information about your medical history from your personal healthcare professional. The more medical history you can provide, the better the diagnosis the doctor can make.
Some of the important things to consider are: your family member’s relevant issues e.g. if someone has or had hypothyroidism; changes in your medical condition recently; the medication you are in, if any; and whether you have had any thyroid issues in the past.
The Physical Exam
The physical examination will help in identifying any physiological symptoms. These signs may include: skin dryness, relatively slower heart rate and reflexes, and swelling in the legs and around eyes.
Why Are Symptoms Not Enough For A Diagnosis?
The endocrinologist is careful when diagnosing thyroid dysfunction. This is because most of the symptoms of hypothyroidism are common issues that people complain about. People might show these without having any thyroid dysfunction.
Therefore, doctors need to be holistic as stated earlier. Also, one way to rule out the common nature of the symptoms is to wait and see how long they continue for. For example, since when have you been feeling low energy or feeling cold while others are at normal temperature?
If you develop new symptoms then maybe it’s a thyroid issue, however, an endocrinologist can make the correct diagnosis. Let’s go over the tests that your doctor will use to check for thyroid dysfunction.
1- TSH Test
It is a primary test for thyroid function evaluation that observes the TSH levels by milli- international units per litre of blood in the blood sample. The normal TSH range is between 0.4 mIU/L-4.0 mIU/L.
TSH levels higher than 4.0 indicate primary hypothyroidism, that is, the thyroid gland is under producing thyroid hormones whereas a level lower than 0.4 would be an indication of an overactive thyroid gland with extra hormone production, suggesting primary hyperthyroidism. Secondary hypothyroidism, although highly uncommon, can also be considered in case an abnormality is observed in the pituitary gland, which would prevent it from producing adequate amounts of TSH.
2- T4 Test
Also known as the FT4 (Free T4) or FT4I (Free T4 Index), it is used to measure the amount of free T4 in ‘picomols’ per litre of blood, with the normal level being 9.025.0 pmol/l. Since T4 circulates within the blood in two forms: either bound to proteins or unbound T4, a blood test usually measures the available FT4 or free T4 units.
High levels of FT4 indicate hyperthyroidism, whereas a lower FTI is an indication of hypothyroidism. However, if the T4 level is within the normal range and slightly raised levels of TSH are observed, the patient may be suffering from sub-clinical hypothyroidism which may progress into clinical/primary hypothyroidism if not actively treated with levothyroxine, particularly if the TSH level is higher than 10 mIU/L.
Note that the TSH and T4 tests are usually performed simultaneously for accurate results.
3- T3 Test
Usually performed if the T4 and TSH tests indicate possibilities of hyperthyroidism, T3 tests are used to confirm the results of T4 and TSH tests or determine the presence of hyperthyroidism. The normal level of T3 in a healthy individual should be 3.57.8 pmol/l or 100-200 ng/dL (nanograms per decilitre).
Levels of T3 higher than this are usually taken as confirmation of hyperthyroidism. Patients with low TSH levels, normal T4 and elevated T3 levels are also considered hyperthyroidic. However, abnormally high levels of T3 could be a prognosis of Grave’s Disease, an autoimmune disorder associated with hyperthyroidism.
Normal TSH, T4 and T3 ranges for pregnant and birth-control taking women slightly differ from other individuals. The commonly referenced TSH range is 0.4–2.5 mU/l in the first trimester and 0.4–3.0 mU/l in the second and third trimesters while T4 and T3 levels are usually much higher than average.
If you observe any symptoms relevant to thyroid disorders or are suffering from them, get these thyroid function tests done immediately. For help, do not hesitate to Book an Appointment with a Top Endocrinologist in Karachi, Peshawar and Islamabad through . Or call our helpline at 042-3890-0939 for assistance to find the RIGHT Doctor for your Thyroid needs.
