INTACT SERUM PARATHYROID-HORMONE LEVELS INCREASE DURING RUNNING EXERCISE IN WELL-TRAINED MEN

The purpose of this study was to examine the influence of exercise on the serum concentrations of intact parathyroid hormone (PTH). Serum PT H and plasma lactate were measured in 15 well-trained men, 9 long-dist ance runners and 6 fire-fighters, during two running exercises. Test o ne consisted of 40-minute treadmill running with a stepwise increased load and test two consisted of 50-minute treadmill running with a cons tant velocity. When the load was step-wise increased, the PTH concentr ations increased moderately at the slower running paces but reached a final value that was about 50% higher than the starting value. This ri se occurred despite a concomitant increase of total serum calcium from 2.38 +/- 0.06 to 2.49 +/- 0.05 mmol/liter (P < 0.01). During the cons tant running exercise, the long-distance runners, but not the fire-fig hters, displayed a significant increase in PTH concentrations although the rise in total serum calcium was similar in both groups. There was a weak correlation between the changes in PTH and lactate in both exe rcises. The findings demonstrate that both high and low intensity exer cise enhance release of PTH in long-distance runners through a mechani sm that does not involve serum calcium. This relationship might be of importance for bone mass in men performing long-distance training.