Which of the following statements about regulation of thyroid hormones is true?
a) TSH positively feeds back on the hypothalamus causing TRH release
b) T3 and T4 negatively feed back on the pituitary to reduce TSH release
c) T3 and T4 negatively feed back on the pituitary to reduce TRH release
d) TSH negatively feeds back on the hypothalamus to reduce TRH release
e) Both b and d are true
Answer: b) T3 and T4 negatively feed back on the pituitary to reduce TSH release
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