What is the process of TRH & TSH when stimulating thyroid hormones?
1. Low levels of T3 & T4 or low metabolic rate stimulate the hypothalamus to secrete TRH
2. TRH enters the hypophyseal portal veins and flows to the anterior pituitary, where it stimulates thyrotrophs to secrete TSH
3. TSH stimulates virtually all aspects of thyroid follicular cell activity, including iodide trapping, hormone synthesis and secretion, and growth of the follicular cells
4. The thyroid follicular cells release T3 & T4 into the blood until the metabolic rate returns to normal
5. An elevated level of T3 inhibits release of TRH and TSH (negative feedback inhibition)