What Do High & Low TSH Levels Mean?

The thyroid gland, located at the front of your neck, produces hormones called T3 and T4 that regulate many bodily functions. Some functions that are controlled by the thyroid gland include temperature regulation, heart rate, brain development, and metabolism. Hyperthyroidism occurs when your thyroid gland is overactive and producing too much T3 and T4, while hypothyroidism occurs when your thyroid gland is underactive and not producing enough of these hormones. 

When to Get TSH Levels Checked

According to Penn Medicine, your healthcare provider may recommend that you get your TSH levels checked if you: 

• Experienced significant weight change without changing your eating or exercise habits
• Notice differences in the appearance of your skin, such as dryness, redness, itchiness, puffiness, or swelling near the base of your neck
• Are always tired, experiencing muscle weakness, or joint pain
• Are always either hot or cold
• Are not pregnant but are missing your period
• Are planning on getting pregnant. It is important that TSH levels are normal before pregnancy
• Recently started thyroid therapy and your doctor wants to recheck your TSH levels

In addition, at birth baby’s TSH levels are checked to ensure proper brain development. 

What TSH Is

TSH, or thyroid-stimulating hormone, is released by the pituitary gland, which is a small endocrine gland located at the base of your brain. TSH levels measure if the thyroid gland is overactive or underactive. 

When the thyroid levels in your body are low (hypothyroidism), your pituitary gland will produce more TSH and when the thyroid levels in your body are high (hyperthyroidism), the pituitary gland will produce less TSH. Therefore, your TSH levels can show how well your thyroid gland is functioning and if there are any abnormalities.