This study will evaluate whether commonly used blood pressure medications called "ACE inhibitors" can lower parathyroid hormone.

The RAAS-PARC study will evaluate whether angiotensin-converting enzyme inhibitors (ACEi) can lower parathyroid hormone (PTH) in normal controls and in individuals have a diagnosis of primary hyperparathyroidism.

Emerging data has implicated the renin-angiotensin-aldosterone system (RAAS) activity with increased PTH. The principal investigator, and other investigators, have previously shown that inhibiting the RAAS may lower PTH. The current study will focus on:

1. Normal Physiology: Does an ACEi (which lowers angiotensin II and aldosterone) reduce PTH in normal individuals?
2. Pathophysiology: Does an ACEi reduce PTH in individuals with primary hyperparathyroidism?

The results of this study may have important implications for cardiovascular and skeletal health, as both the RAAS and PTH have been implicated as mediators of these conditions.

Inclusion Criteria:

• Healthy subjects with with no medical problems (n=15) and individuals with primary hyperparathyroidism (n=30)
• normal blood pressure or stage 1 hypertension that is either untreated, or adequately treated with a single anti-hypertensive medication.
• Age >18 years and <80 years
• Estimated GFR > 60ml/min

Exclusion Criteria:

• Chronic Kidney Disease or eGFR<60
• Stage 2 or Stage 3 hypertension or the use of more than 1 antihypertensive drug
• Type 2 Diabetes Mellitus that is not controlled by diet or Metformin alone or with a Hemoglobin A1c >7.5%
• History of liver failure
• History of heart failure
• The use of typical or atypical antipsychotic medications or lithium.
• Chronic inflammatory conditions (such as inflammatory bowel disease or arthritis) that are treated with prescribed doses of NSAIDs or glucocorticoids
• The use of prescribed doses of potassium supplements.
• Illness requiring overnight hospitalization in the past 6 months
• Active tobacco or recreational drug use
• Pregnancy or current breast feeding

4 years

This a small physiology pilot study that is open-label and non-randomized. The intervention was an ACE inhibitor, an approved therapy. Results have physiologic implications, but treatment implications are not intended.

Open Label