Thyroid Stimulating Hormone (TSH) is a hormone produced by the pituitary gland that regulates the function of the thyroid gland. It stimulates the thyroid to produce thyroid hormones (T3 and T4), which are critical for metabolism, growth, and development.

High TSH Levels: Elevated TSH usually indicates an underactive thyroid (hypothyroidism), where the thyroid gland isn’t producing enough hormones, prompting the pituitary to produce more TSH to stimulate the thyroid.

Low TSH Levels: Low levels often suggest an overactive thyroid (hyperthyroidism), where excessive thyroid hormone production suppresses TSH release from the pituitary gland.