β-Adrenergic Blockade Augments Pulsatile PTH Secretion in Humans

Pulsatile peptide hormone secretion provides efficient control of specific end organ functions. To test the hypothesis that sympathetic neuronal activity drives synchronous pulsatile PTH release from the parathyroid glands, we investigated the acute effects of β-adrenergic receptor blockade on PTH secretion patterns in a single-blinded study in nine healthy adults. Plasma PTH levels were determined at 1-min intervals. After a 75-min baseline period, seven subjects received a continuous intravenous infusion of the short-acting β-adrenergic receptor blocker esmolol for 105 min. After a 30-min washout period, esmolol was infused for another 30 min. Two additional subjects were randomized to receive solvent infusions. PTH secretion characteristics were analyzed by multiparameter deconvolution analysis, and the orderliness of plasma PTH fluctuations by Approximate Entropy statistics. BP slightly decreased during esmolol infusion, whereas heart rate, ionized calcium, phosphate, magnesium, and plasma and urine catecholamines remained unchanged. Esmolol increased mean plasma PTH by 33 ± 8% (P < 0.01), due to a preferential increase in the pulsatile PTH secretion component (+ 129 ± 44%, P < 0.02). The increased pulsatile PTH secretion was mediated by an augmented PTH burst mass (+ 117 ± 42%, P < 0.01), whereas burst frequency remained unchanged. The regularity of PTH fluctuations was not affected by the β-adrenergic blockade. The effects were reproducible during the second esmolol infusion. The authors conclude that the sympathetic nervous system has a modulating effect on pulsatile PTH secretion. Selective β-1 adrenergic blockade acutely increases plasma PTH by augmenting the mass of hormone secreted per burst, but it does not alter the rhythmicity of pulsatile PTH release.