The normal thyroid-stimulating hormone range is 0.4 to 4.0 milli-international units per liter, according to MedlinePlus. In children, the normal TSH level is 0.7 to 6.4 microunits per milliliter. For newborns, a normal level of TSH is 1 to 39 microunits per milliliter. However, this range may vary from one lab to another, as different labs may use different sample tests. Measurement differences among labs also cause the normal range variation.
When the level of the thyroid-stimulating hormone, or TSH, is abnormally high, the implication is that the patient may have hypothyroidism, which is an underactive thyroid gland, explains MedlinePlus. When the TSH level is abnormally low, the patient may have hyperthyroidism, which is an overactive thyroid gland. The causes of lower-than-normal TSH levels include multinodular goiter, excessive body iodine and Graves' disease. Women often experience low TSH levels during the first trimesters of their pregnancies.