It is a fact that hormone imbalance is the basic cause of various diseases and disorders. Thyroid gland, situated in the neck, releases the hormone triiodothyronine (called T3) and thyroxine hormone (called T4). The hormone released by the pituitary gland stimulates the release of thyroid hormones and hence it is known as thyroid stimulating hormone (TSH). When symptoms of abnormal thyroid function are noticed, a simple blood test known as TSH blood test is performed to measure the amount of TSH in blood.
Thyroid Hormone Levels and TSH
When the thyroid gland does not release sufficient hormones, the condition is described as hypothyroidism. As TSH is required to trigger the secretion of thyroid hormones, more TSH is released by the pituitary gland to stimulate the thyroid gland. Elevated levels of TSH thus indicate thyroid dysfunction or decreased levels of thyroid hormones. The condition wherein excessive production of thyroid hormones is noticed is known as hyperthyroidism. Very high levels of the hormones released by thyroid gland are characteristic of an overactive thyroid gland. The pituitary gland therefore restricts the flow of TSH. Thus, as a result of increased flow of thyroid hormones, TSH levels drop down. Here is a chart that provides information on the normal levels of the hormones released by thyroid gland.
Normal Thyroid Level Chart
Hormones Normal Range (mIU/L) Interpretation
T3 (Serum triiodothyronine) 80 – 220 T3<80 indicates hypothyroidism.
Total T4 (Serum thyroxine) 4.5 to 12.5 T4<4.5 with elevated TSH indicates under-active thyroid. T4>12.5 indicates hyperthyroidism. T4<4.5 with low TSH suggests a pituitary problem.
TSH 0.3 to 3.0 (as of 2003, revised by the American Association of Clinical Endocrinologists) but many labs or doctors follow the old numbers 0.4 to 6 TSH<0.3 indicate hyperthyroidism and TSH>3.0 indicate hypothyroidism.
Along with ‘total T4’ levels, levels of ‘Free T4’ are also measured. 0.7 to 2.0 is considered as normal range for ‘Free T4’. Similarly, ‘Free T3’ levels are also measured and 2.3 to 4.2 is the normal range of ‘free T3’.
Low Thyroid Levels
Children may naturally exhibit slightly higher TSH level (or low thyroid levels) when compared to adults. Thyroid hormones determine the rate of metabolism. Low levels of these hormones may lead to low basal metabolic rate resulting in loss of appetite, increased fatigue, weakness. The person may notice increased somnolence all the time, and suffer from frequent attacks of cold. He may experience joint pain, swelling in the neck, dry skin, hair loss, hoarse voice, etc. In spite of dieting, he may not be able to control his cholesterol levels.
High Thyroid Levels
An overactive thyroid can cause hot flashes, irregular heartbeat, nervousness resulting in depression and weight loss. Women usually complain about joint pain and irregular menstrual cycles when they have elevated thyroid levels. Confusion or poor concentration is also noticed sometimes. Hyperthyroidism in men may result in impotence, rapid heart rate, increased bowel movement, heat intolerance, palpitations, arrhythmia, profuse sweating, increased irritability, decreased concentration, weight loss, tremor, insomnia and depression.
To assess the thyroid function, TSH test alone cannot provide sufficient information. Similarly measuring T3 and T4 levels, without measuring TSH levels will not be useful for diagnosing thyroid problems. It is essential to measure T3, T4 and TSH levels simultaneously to detect the cause of abnormal thyroid activities.
Prescribed medicines and specially designed thyroid diet help manage the symptoms of abnormal thyroid function. The element ‘iodine’ in your diet, plays an important role in maintaining thyroid health. Normal levels for thyroid hormones may slightly vary from person to person. I hope you found the above chart and the information, helpful. Thyroid levels keep on fluctuating, so consult your doctor for correct interpretation of the thyroid test results.