1. Twenty-four patients with primary hyperparathyroidism were studied before and 18 restudied 6.5 months (mean) after parathyroidectomy, to investigate the pathogenesis of the hypertension which may accompany this condition. Comparison was made with age-matched patients with essential hypertension and with normotensive control subjects.
2. There was a significant inverse relationship between mean arterial pressure and 51Cr-labelled ethylenediaminetetra-acetate (51Cr-EDTA) clearance in patients with hyperparathyroidism both before and after parathyroidectomy, but not in patients with essential hypertension.
3. Creatinine clearance appeared to overestimate glomerular filtration rate in some patients with hyperparathyroidism, falling significantly after surgery while 51Cr-EDTA clearance was unchanged. This observation may explain the failure of some previous studies to relate hypertension to impairment of renal function.
4. Plasma renin activity, plasma aldosterone and whole-body exchangeable sodium did not differ between normotensive and hypertensive patients with primary hyperparathyroidism and were unchanged after surgery.
5. Parathyroidectomy did not result in any change in blood pressure or in glomerular filtration rate measured by 51Cr-EDTA clearance.