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Control of thyroid hormones, like many other hormones, is accomplished by negative feedback (see attachment). Should the metabolic rate decrease, receptors in the hypothalamus are activated.Nerve cells secrete thyroid-releasing hormone (TRH), which stimulates the pituitary to release thyroid-stimulating hormone (TSH). Thyroid-stimulating hormone is carried by the blood to the thyroid gland, which, in turn, releases thyroxine. Thyroxine raises metabolism by stimulating increased sugar utilization by body cells. Higher levels of thyroxine cause the pathway to be “turned off.”Thyroxine inhibits the release of TRH from the hypothalamus, thus turning off the production of TSH from the pituitary.