Treadmill Running Reduces Parathyroid Hormone Concentrations During Recovery Compared With a Nonexercising Control Group

Context: Lower PTH concentrations reported in the hours after acute, endurance exercise compared with preexercise levels might be influenced by factors such as circadian fluctuations. Objective: The objective of the study was to compare postexercise PTH concentrations with a nonexercising control group. Design and Setting: A laboratory-based study with a crossover design, comparing a 60-minute (at 10:30 AM) bout of treadmill running at 65% of the maximal rate of oxygen uptake (exercise) with semirecumbent rest (CON). Blood samples were obtained immediately before (baseline 10:15 AM) and after (11:30 AM) exercise and during recovery (12:30 AM, 1:30 PM, and 2:15 PM). Participants: Ten physically active men(mean +/- 1 SD, age 26 +/- 5 y; body mass 78.3 +/- 5.8 kg; maximal rate of oxygen uptake 57.3 +/- 6.9 mL/kg(-1) . min(-1)) participated in the study. Main Outcome Measures: PTH, albumin-adjusted calcium, and phosphate concentrations were measured. Results: PTHconcentrations increased (+85%, P < .01) during exercise and were higher than in CON immediately at the end of exercise (4.5 +/- 1.9 vs 2.6 +/- 0.9 pmol/L-1, P < .05). In the postexercise period (12:30-2:15 PM), PTH was not different compared with baseline but was lower compared with CON at 1:30 PM (-22%; P < .01) and tended to be lower at both 12:30 PM (-12%; P = .063) and 2:15 PM (-13%; P = .057). Exercise did not significantly affect the albumin-adjusted calcium concentrations, whereas phosphate was higher than CON immediately after exercise (1.47 +/- 0.17 vs 1.03 +/- 0.17 pmol/L-1, P < .001) and was lower at 1:30 PM (-16%; P < .05). Conclusions: Lower PTH concentrations after acute endurance running compared with a rested control condition suggest a true effect of exercise.