A person with symptoms of hypothyroidism (for example, sluggishness and intolera

Question

A person with symptoms of hypothyroidism (for example, sluggishness and intolerance to cold) is found to have abnormally low plasma concentrations of T4, T3, and TSH. After an injection of TRH, the plasma concentrations of all three hormones increase. Where is the site of the defect leading to the hypothyroidism? A full-term newborn infant is abnormally small. Is this most likely due to deficient growth hormone, deficient thyroid hormones, or deficient in utero nutrition? A patient with symptoms of hyperthyroidism is found to have circulating antibodies against the receptors for TSH. Can you deduce the cause of the hyperthyroidism?

Explanation / Answer

Answer 4.

TRH or TRF stands for Thyrotropin releasing hormone/factor. It is produced from the hypothalamus. This hormone instructs anterior pituitary to release TSH (Thyroid stimulating hormone). TSH then instructs thyroid glands to make T3 and T4.

Therefore, the site of defect in this patient is the hypothalamus.

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