[Relation between the parathyroid glands and arterial pressure: is there a parathyroid hypertensive factor?]

Parathyroid hypertensive factor (PHF) is a newly discovered circulating factor that has been implicated in some forms of hypertension. Such an involvement has been established in several animal models and in hypertensive patients. PHF originates from the parathyroid glands. This explains why hypertensive individuals often have high levels of circulating parathyroid hormone (PTH), which is itself hypotensive. This would reflect the activity of the parathyroid glands, which would produce PHF concomitantly with PTH. The mechanism of action of PHF involves an increase in calcium-channel activity in vascular smooth muscle cells. The opening of these channels would lead to increase calcium entry into these cells, resulting in increased sensitivity to other vasoconstrictors. PHF level explains why a high calcium diet may be effective in lowering blood pressure in patients who respond to calcium-channels blockers: dietary calcium might inhibit the production of PHF (and PTH), whereas calcium-channels blockers would inhibit PHF at its target site.