A TSH level below the normal range may indicate hyperthyroidism, where thyroid hormone levels are too high. This could result from the thyroid gland itself producing too much hormone, or external factors (such as excessive iodine intake) stimulating thyroid hormone production.
TSH levels are below the normal range, but free thyroid hormones (FT4 and FT3) remain within normal limits. This condition often requires further monitoring to determine if there are signs of hyperthyroidism.
Low TSH levels may occur due to weakened feedback regulation of thyroid hormones by the hypothalamus or pituitary gland, leading to decreased TSH secretion.
Patients on long-term thyroid hormone replacement therapy may have TSH levels below the normal range.