Can Losartan change blood pressure in three days?

Hello doctor,

My blood pressure went up to 169/100 mm of Hg a couple of days before a scheduled stress Echo. My T4 is elevated and my Synthroid dose is being tweaked and I am three weeks into that. I am a 68-year-old woman in good health and not overweight and have not had a history of hypertension. An internist that I saw thought I needed to be medicated. I started Losartan (25 mg) once a day for three days. I had the stress Echo yesterday and my blood pressure before the test was 159/96 mm of Hg. Afterward, it was 138/94 mm of Hg. Today it is down 120/80 mm of Hg in the am and the same this afternoon. I have not taken the 25 mg of Losartan for 28 hours now. Do I need to continue? Could the three doses of Losartan be responsible for the change or just the relief that the test is over? I would prefer not to be medicated unnecessarily. I eat a healthy diet and do not smoke or drink alcohol. Is there a need to taper off the Losartan and how would I? My thyroid glands are suppressed because 68 years ago my thymus gland was radiated because I sounded raspy. I have had no issues but have been on Synthroid for 48 years. A few times I have had to change my dose. Currently, my T4 is elevated, and l landed in the ER three weeks ago with stomach, chest, and left arm pain. I had a full workup for my heart and CT abdominal scan with contrast and everything checked out WNL. I found out a few days later about the elevated T4. Three years ago this happened and my Synthroid dose was adjusted and I felt better in a few weeks. I am currently on Pravastatin 20 mg and vitamin D medication for three days.