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 morning, and it is 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 a 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. 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.

Thank you.