hello and thank you for asking HCM, I understand your concern. Normal blood pressure is everything under 140/90. Your brother have a diastolic number — the bottom number of a blood pressure measurement — less than 90 millimeters of mercury (mm Hg) and a systolic number — the top number of a blood pressure measurement — greater than 140 mm Hg, so he has a common type of high blood pressure called isolated systolic hypertension. Since your brother has hypothyreoidism, your doctor made a good decision to gave him blood pressure therapy, because hypothyroidism triples the risk of developing high blood pressure, and your brother already has high systolic blood pressure. I hope this answer was helpful to you.