The hypothalamus produces the thyroid-releasing hormone (TRH), a small molecule derived from a tripeptide. This stimulates release of the thyroid-stimulating hormone (TSH), a glycoprotein produced by the pituitary. TSH stimulates the thyroid gland to secrete thyroxine (T ₄ ), a small molecule derived from the amino acid tyrosine. Thyroxine increases the metabolic rate of many cells in the body. High levels of thyroxine inhibit both TRH production by the hypothalamus and TSH production by the pituitary.

Construct a model to show how these various factors are involved in cell communication pathways in the body.