T3 (TRI IODO THYRONINE)

• 60-200 ng/dl

Paediatric normal range

• 1-3 days-100 to 740 ng/dl
• 1-11 months -105 to 245 ng/dl

• Triiodothyronine (T3) is one of the two major hormones produced by the Thyroid Gland. Almost all of the T3 found in the blood is bound to protein; the rest is free (Unbound) and is the biologically active form of the hormone. T3 levels are regulated by the feedback system that the body uses to maintain stable amounts of Thyroid hormones in the blood.
• If the Thyroid releases excess amounts of T4 and T3, there will be symptoms associated with Hyperthyroidism (Rapid heart rate, weight loss, nervousness, hand tremors, irritated eyes, difficulty sleeping). Graves disease is the most common cause of Hyperthyroidism.
• If there is decreased production of Thyroid hormones, there will be symptoms associated with Hypothyroidism (weight gain, dry skin, constipation, cold intolerance, fatigue). Hashimoto Thyroiditis is the most common cause of Hypothyroidism.
• T3 measurements are especially valuable in diagnosing hyperthyroidism, T3 Thyrotoxicosis and in conditions caused by iodine deficiency.

• When there are s/s of Hyperthyroidism (Increased heart rate, Anxiety, weight loss, difficulty sleeping, tremors in the hands, weakness, Menstrual irregularity

• Hyperthyroidism
• Inadequately treated Hyperthyroidism
• Excessive treatment for Hypothyroidism
• Patients on T3 treatment
• T3 Toxicosis

• Depressed levels may occur during severe illness
• Malnutrition
• Renal failure
• During therapy with antithyroid drugs propranolol, propylthiouracil and salicylates
• Euthyroid sick syndrome