A TSH, or thyroid-stimulating hormone, level of 100 is very high, and it rests well above the normal range of 0.4 to 4.2 microunits per milliliter for healthy adults. A level of 100 even greatly surpasses expected TSH levels for newborns, which reach up to 39 microunits per milliliter.
A TSH level of 100 results from hypothyroidism. This means the pituitary gland produces high levels of TSH to account for the lack of hormones produced by the thyroid. It is most likely attributable to Hashimoto's thyroiditis, the most prevalent form of primary hypothyroidism.
Although possible, high TSH levels rarely originate from overproduction by a pituitary gland tumor. TSH levels prove to be inadequate for diagnosis and treatment of the core problem. Therefore, it is important to consult a physician about further tests for discovery.