Thyroid-stimulating hormone (TSH) is a hormone produced by the pituitary gland that regulates the function of the thyroid gland, which in turn controls metabolism, energy levels, and growth. TSH stimulates the thyroid to produce and release thyroid hormones, mainly thyroxine (T4) and triiodothyronine (T3), maintaining a delicate balance in the body’s metabolic processes. Abnormal TSH levels can indicate thyroid dysfunction: elevated TSH may suggest an underactive thyroid (hypothyroidism), while low TSH can indicate an overactive thyroid (hyperthyroidism). Measurement of TSH in the blood is a key diagnostic tool for assessing thyroid health and guiding treatment decisions.