Anatomy and Physiology II (APII) Milestone 1 Practice Test

Negative feedback in this axis is when rising thyroid hormones signal the brain to dial back the signals that drive their production. The hypothalamus releases TRH, which tells the pituitary to secrete TSH, and TSH then prompts the thyroid to produce T3 and T4. When T3 and T4 levels get high, they suppress TRH and TSH release, reducing further thyroid hormone production and keeping levels balanced. The sequence where elevated thyroid hormone levels inhibit TRH and TSH secretion best describes this feedback inhibition. The other statements describe the initial drive to increase production when thyroid hormone is low or mix up which gland controls which step, so they don’t capture the feedback stopping point.