Dr Siddiqui calls Angela and asks her to come back to the di

Dr. Siddiqui calls Angela and asks her to come back to the dink to discuss her results. It appear! that Angela has a hormone suppressing tumor in cither the hypothalamus or anterior pituitary Dr Siddiqui wants to do some tests to confirm a tumor and determine where the tumor it located. Dr. Siddiqui recommends that Angela go for an MRI, a CAT scan or a PET scan to tee if a tumor is visible. She also recommends a TRH challenge test. Knowing what you do about the HPT axis, what hormonal information would you need to determine if the hormone-suppressing tumor is in the hypothalamus or anterior pituitary? Why is it near impossible to get this information? Dr. Siddiqui injects Angela with a dose of TRH and draws a blood sample to measure TSH and thyroid hormone levels. What results would you expect if the tumor is in the hypothalamus? The anterior pituitary? Use the table below to organize your answers (state high or low) and then explain your rationale for your answer below.

Solution

To determine the location of hormone supressing tumour, thyroid releasing hormone (TRH) is given to observe the release of thyroid stimulating hormone (TSH). If the level rises after TRH administration, the defect is with hypothalamus. If the TSH levels do not rise, the defect is with anterior pituitary. However, false positive or negative results are possible with this test.