Expression of parathyroid hypertensive factor in hypertensive primary hyperparathyroid patients

Hypertension is frequently associated with primary hyperparathyroidism, yet the mechanism of such hypertension is unknown. Parathyroid hypertensive factor (PHF) is a circulating hypertensive factor found in a proportion of human essential hypertensive patients as well as in spontaneously hypertensive rats (SHR). In the latter case, PHF has been shown to be secreted by the parathyroid gland. The purpose of this study was to determine if PHF expression might be responsible for the hypertension seen in primary hyperparathyroidism. Ten hypertensive and 10 normotensive primary hyperparathyroid patients underwent measurement of blood pressure and PHF pre- and post-parathyroidectomy. Cases reported are those of parathyroid adenomas. There were no significant differences between the hypertensive and normotensive groups preoperatively except that 9 out of 10 of the hypertensive group had significant PHF levels (mean 11 +/- 2 mm Hg vs 0.6 +/- 2 mm Hg, respectively, p = 0.003). Post-operative change in mean arterial pressure could be predicted by pre-operative PHF level, with all PHF-positive patients showing a fall in blood pressure (r = -0.73, p < 0.01). Post-operatively, PHF was undetectable in PHF-positive patients. These results suggest that the parathyroid gland can express PHF in humans and that such expression may be responsible for a proportion of the high reported incidence of hypertension in primary hyperparathyroidism.