Thyroid & EndocrineNo Fasting RequiredTurnaround: 6–12 hours (same day)

Thyroid Profile (TFT: TSH, Free T3, Free T4)

Also known as: Thyroid Function Test, TFT, TSH with Free T3/T4, Thyroid Panel Complete

Parameters Measured in the Report

A breakdown of individual biomarkers and biological reference intervals typically found in your report:

Biomarker	Standard Range	Unit	What It Means
Thyroid Stimulating Hormone (TSH) (Thyrotropin)	0.45–4.50 (Target in pregnancy or therapy varies)	µIU/mL (mIU/L)	Pituitary hormone regulating thyroid production; the most sensitive single marker of thyroid axis status.
Free T4 (FT4) (Free Thyroxine)	0.8–1.8	ng/dL	The active, unbound fraction of thyroxine circulating in blood available to body tissues.
Free T3 (FT3) (Free Triiodothyronine)	2.3–4.2	pg/mL	The most metabolically potent thyroid hormone; converted from T4 primarily in the liver and kidneys.
Total T4 (Total Thyroxine)	4.5–12.0	µg/dL	Total T4 including hormone bound to transport proteins (thyroxine-binding globulin).
Total T3 (Total Triiodothyronine)	80–200	ng/dL	Total T3 in circulation; sensitive marker in evaluating thyrotoxicosis/hyperthyroidism.

* Note: Reference ranges may vary slightly between testing instruments and reagent kits. Always refer to the reference interval printed on your specific pathology report.

Clinical Focus

Thyroid Stimulating Hormone (TSH), Free Thyroxine (FT4), and Free Triiodothyronine (FT3).

Sample & Specimen

Venous blood (Serum tube)

Fasting Protocol

Fasting is not required, but early morning collection (8:00 AM–10:00 AM) is recommended.

Turnaround Time

6–12 hours (same day)

What Is This Test?

The Thyroid Profile evaluates the health of your thyroid gland — a butterfly-shaped endocrine organ located at the base of your neck. The thyroid produces two master metabolic hormones: Triiodothyronine (T3) and Thyroxine (T4), which dictate your basal metabolic rate, body temperature, cardiac rhythm, and cellular energy expenditure. The master control system lives in your pituitary gland in the brain, which secretes Thyroid Stimulating Hormone (TSH). Through a tight negative feedback loop, if thyroid hormone levels in the blood drop, the pituitary responds by pumping out more TSH to urge the thyroid to work harder.

Why Did Your Doctor Order This Test?

Physicians routinely prescribe the Thyroid Panel in the following clinical scenarios:

Suspected Hypothyroidism: unexplained weight gain, chronic fatigue, cold intolerance, constipation, hair loss, brain fog

Suspected Hyperthyroidism: rapid unintentional weight loss, racing heart (palpitations), heat intolerance, tremors, anxiety

Evaluation of menstrual irregularities, heavy periods, or female infertility

Routine monitoring and dosage titration of levothyroxine or antithyroid medications

How to Prepare Before Your Test

Fasting Requirement: Fasting is not required, but early morning collection (8:00 AM–10:00 AM) is recommended.

Morning blood collection is ideal because TSH levels follow a diurnal rhythm and peak in the early hours.
If you take daily thyroid medication (e.g., Levothyroxine), consult your doctor — most recommend taking your morning pill AFTER the blood draw.
Stop taking high-dose Biotin (Vitamin B7) supplements at least 48 to 72 hours prior, as biotin interferes with laboratory immunoassay reagents and causes falsely abnormal readings.

Understanding Your Results

What higher or lower readings generally mean in clinical practice:

If Values Are Higher Than Normal

Elevated TSH (>4.5 µIU/mL) combined with low FT4 indicates Primary Hypothyroidism (underactive thyroid), most commonly caused by Hashimoto’s autoimmune thyroiditis. Elevated TSH with normal FT4 represents Subclinical Hypothyroidism.

If Values Are Lower Than Normal

Suppressed or low TSH (<0.4 µIU/mL) combined with elevated FT4 and FT3 indicates Hyperthyroidism (overactive thyroid), commonly caused by Graves’ disease or toxic nodular goiter. Symptoms include rapid pulse, sweating, insomnia, and tremors.

Frequently Asked Questions

Why did my doctor only order TSH instead of the full T3/T4 profile?

TSH is the most sensitive first-line screening test. A slight shift in thyroid hormone levels triggers an amplified change in TSH. If TSH is normal, full thyroid disease is very unlikely; if TSH is abnormal, reflex Free T4 testing is done.

Why does Biotin (hair/skin supplement) interfere with thyroid tests?

Many diagnostic lab instruments use biotin-streptavidin technology to bind and measure thyroid hormones. High supplemental biotin in the blood binds to test reagents, leading to falsely high FT3/FT4 and falsely low TSH.

Related Laboratory Tests

Tests frequently prescribed together or used as follow-up investigations:

Complete Blood Count (CBC / Hemogram)

Counts and evaluates red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.

Lipid Profile (Cholesterol Panel)

Total Cholesterol, HDL (good cholesterol), LDL (bad cholesterol), VLDL, and Triglycerides.

Intact Parathyroid Hormone (iPTH)

Biologically intact 84-amino acid polypeptide hormone secreted by the four parathyroid glands.

Vitamin D3 (25-Hydroxy Vitamin D)

Total circulating concentration of 25-hydroxyvitamin D (D2 and D3 combined).

Medical & Diagnostic Disclaimer

This guide is published for educational and patient informational purposes only. It is not a substitute for professional medical evaluation, diagnosis, or clinical advice.

A laboratory result that falls slightly outside standard statistical reference intervals does not automatically indicate disease; conversely, a normal result does not guarantee the absence of medical conditions. Only your attending physician can interpret lab findings in the context of your medical history, physical exam, and symptoms.