A 20-year-old male presents with weight loss, heat intolerance, bilateral exophthalmos, a lid lag, sweating, and tachycardia. These symptoms are due to an increased production and secretion of a hormone that is derived from which one of the following?

The patient has Graves' disease hyperthyroidism, an overproduction of thyroid hormone, which is derived from tyrosine. Hyperthyroidism increases the rate of oxidation of fuels by muscle and other tissues, increasing heat production, and causes a sense of heat intolerance and increased sweating. The heart rate and blood pressure are also increased, as is weight loss in spite of a healthy appetite. Dopamine (a catecholamine) is also derived from tyrosine and can be hydroxylated to norepinephrine, which can then be methylated to epinephrine, but the catecholamines cannot be transformed to thyroxine. Tryptophan can be metabolized into serotonin and melatonin. Cholesterol is the basis of the steroid hormones progesterone, testosterone, E2 , cortisol, and aldosterone. Glutamate gives rise to GABA via a decarboxylation reaction.