Low TSH levels can be caused by pituitary gland tumors, which are almost always benign (not cancerous). If a tumor is detected, you’ll receive hormone or radiation therapy, or have it surgically removed. Cases of low TSH levels due to a pituitary gland disorder are rare.

The standard reference range for the TSH level is anywhere between 0.30 and 5.0 uIU/mL. If your TSH level is higher than 5.0 uIU/mL, then the lab will flag you as “high,” and you may experience the symptoms listed above 5.0 uIU/mL. Values of the TSH level more than 10.0 uIU/mL need long-term thyroid supplements.

Normal TSH ranges can vary widely, depending on a person’s age, sex, and body weight. Reference ranges remain controversial, but for most people, the normal range falls between 0.4 and 4.0 mU/l.

High TSH levels can mean your thyroid is not making enough thyroid hormones, a condition called hypothyroidism. Low TSH levels can mean your thyroid is making too much of the hormones, a condition called hyperthyroidism.

If your TSH levels are abnormally high, it could mean you have an underactive thyroid, or hypothyroidism. That’s because it indicates your pituitary gland is producing more TSH in an effort to stimulate your thyroid to produce thyroid hormone, according to the Mayo Clinic.

The normal TSH range is 0.4 to 5 milli-international units per liter (mIU/L). If your level is higher than this, chances are you have an underactive thyroid. Pregnancy can also make your TSH levels higher.

Serious complications can result from low TSH levels.These complications can include a variety of heart problems, weak bones, eye and skin problems, and thyrotoxic crisis—a serious condition that can cause delirious behavior. Seek medical care if your symptoms increase intensely as this can indicate thyroxic crisis.

High level of TSH usually indicates that you have an underactive thyroid and that it doesn’t produce enough thyroid hormones. Thyroid-stimulating hormone (TSH) directly affects how much T3 and T4 hormones the thyroid secretes.