What are expected TSH levels in a patient with hypothyroidism?

In patients with hypothyroidism, it is expected that TSH (thyroid-stimulating hormone) levels are higher than normal. This occurs because when the thyroid gland is underactive and not producing sufficient thyroid hormones (like T3 and T4), the pituitary gland compensates by increasing the production of TSH in an effort to stimulate the thyroid to produce more hormones. As a result, elevated TSH levels are indicative of hypothyroidism, reflecting the body's response to the low levels of circulating thyroid hormones.

Normal TSH levels would suggest that the thyroid is functioning adequately, which is not the case in hypothyroidism. Fluctuating levels may occur in some patients due to various factors, but they are not characteristic of the disease and do not define the expected TSH levels. Thus, higher than normal TSH levels are a critical diagnostic identifier for hypothyroidism.