4. Blood tests to see if the tumor secretes hormones in response to specific stimuli, including exercise, food, and various hormones. The hormones are given through an intravenous catheter, or IV a thin plastic tube inserted into an arm vein. After the stimulus, blood is drawn through the same IV every 30 minutes for up to 3 hours to measure hormone levels. Based on the results of these tests, some patients may have additional blood tests to check hormone response to special foods, an IV salt solution, or other hormones or drugs given either IV or by mouth (in pill form).