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Fig. 2. Role of renal calcium leak in essential hypertension. Hypertensives exhibit an increase in urinary calcium losses, which is exacerbated on high salt diets. This results in a transient decrease in serum ionized Ca2+. The parathyroid gland responds to this decrease with the release of parathyroid hormone (PTH), which activates the renal 1-
-hydroxylase, resulting in increased 1,25-(OH)2-D production. 1,25-(OH)2-D serves as a stimulus to increase vascular smooth muscle intracellular Ca2+.