“Thyroid” usually refers to the thyroid gland, a small butterfly-shaped gland located in the front of the neck. It plays a major role in controlling the body’s metabolism, energy levels, weight, heart rate, and overall hormonal balance.
The thyroid is a small, butterfly-shaped gland located in the front part of the neck. Its main job is to make hormones that control the body’s metabolism — that means how fast your body uses energy, how your heart beats, how your brain works, and how your body grows.
The thyroid is a gland in the neck that controls energy, metabolism, weight, and many body functions through hormones.
It is very important today to know whether a person’s thyroid is functioning properly or if it is higher than what the body requires. That is why doing a thyroid test once every six months is very important.
| Test Name | Unit | Bio. Ref. Interval | Method |
| Thyroid profile Total | |||
| T3, Total | ng/mL | 0.35-1.93 | CMIA |
| T4, Total | μg/dL | 4.87-11.72 | CMIA |
| Thyroid Stimulating Hormone – Ultrasensitive | μIU/mL | 0.35-4.94 | CMIA |
Below mentioned are the guidelines for pregnancy related reference ranges for TSH, total T3 & Total T4.
| Pregnancy | |||
| TSH (μIU/mL) (as per American Thyroid Association ) | Total T3 (ng/mL) | Total T4(μg/dL) | |
| 1st trimester | 0.1-2.5 | 0.81-1.90 | 7.33-14.8 |
| 2nd trimester | 0.2-3.0 | 1.00-2.60 | 7.93-16.1 |
| 3rd trimester | 0.3-3.0 | 1.00-2.60 | 6.95-15.7 |
TSH levels are subject to circadian variation, reaching peak levels between 2 – 4.a.m. and at a minimum between 6-10 pm
.
The variation is of the order of 50%, hence time of the day has influence on the measured serum TSH concentrations.
TSH is secreted in a dual fashion: Intermittent pulses constitute 60-70% of total amount, background continuous secretion is 30-40%.These pulses occur regularly every 1-3 hrs.
Total T3 & T4 concentrations are altered by physiological or pathological changes in thyroxine binding globulin (TBG) capacity .
The determination of free T3 & free T4 has the advantage of being independent of changes in the concentrations and binding properties of the binding proteins.
Changes in thyroid status are typically associated with concordant changes in T3, T4 and TSH levels.
Unexpectedly abnormal or discordant thyroid test values may be seen with some rare, but clinically significant conditions
such as central hypothyroidism, TSH-secreting pituitary tumors, thyroid hormone resistance, or the presence of
Heterothallic antibodies (HAMA) or thyroid hormone autoantibodies. For diagnostic purposes, results should be used in conjunction with other data.
