MRCP2-1606

A 50-year-old female presents with symptoms of depression, constipation, polyuria, and thirst. She has been experiencing tiredness and arthralgia for the past six months since being diagnosed with hypertension and taking bendroflumethiazide 2.5 mg daily. Physical examination is normal except for a blood pressure of 162/94 mmHg. Her lab results show elevated serum sodium and corrected calcium levels, as well as high plasma parathyroid hormone levels. What is the most suitable initial treatment for this patient?